Depth of Field and VFX
This is in response to a question from a reader about depth of field and how it relates to visual effects.
Models
With miniatures you need enough depth of field to hold focus from the front of the model to the back of the model. This means a lot of light and a stopped down lens. Lack of depth of field is one of the key things that give away the look of the model since in real life a large area would be photographed from a further distance and (possibly in sunlight) so depth of field wouldn't be a problem.
Greenscreen/Bluescreen
If you're shooting a greenscreen then you'll typically want to make sure all the foreground people and objects are in sharp focus. This is easily and frequently overlooked, especially by directors of photography. (And at times by the VFX supervisor) If you have a sunlit, exterior background image then it's likely to be shot at f8-f16. This provides a reasonable amount of depth of field. But when the DP lights the stage he probably won't be lighting to same intensity levels. If the lack of depth of field is apparent then it causes two problems. If the back end of the foreground is soft then you're forced to blur the background even if there's something important to see. It's impossible in real life to have only a mid-section that's blurred. If the director really needs to see what's back there then you're forced to try to sharpen the edges and back detail of the foreground. The end result will never appears natural. The other problem is the audience senses that this is unnatural (i.e. they only see this in vfx shots). An 'exterior' scene in bright sunlight with a normal or wide angle lens should be in focus throughout a normal shot.
You'll see animated films where they have cheated the depth of field. I find it best if you want your vfx or animation to appear natural is to use the guidelines and restrictions that a normal movie has. (depth of field, camera movement, etc)
Markers
The other depth of field issues for VFX people is soft tracking markers and very soft edge mattes. If you're on a stage shooting a greenscreen with a long lens then the markers may be so out of focus as to disappear. This is a big problem, especially if you're shooting a character from the waist up who's moving and jumping around. Since the markers are invisible, you have no easy way of distinguishing the camera motion from the character motion. Someone will have to manually work on that shot by eye until it looks reasonable. This can be very time consuming and require a number of takes.
Note that LED markers tend to hold up better for out of focus shots. These are markers using key ring lites (possibly modified) you see in the store. The point source of a red LED holds up better than an X piece of tape.
Mattes
The soft edges of the greenscreen matte (or a place you want the roto matte) will require delicate settings of the key. Any blur (from depth of field or motion) will cause some of the background to bleed through that area as if it were partially transparent. The blurred area then becomes more contaminated with the greenscreen. When rotoing a blurred edge it's sometimes a subjective question where the blur stops. If you include all of the blur then you'll be including some of the original background. If you clip off too much of the blur then it will look incorrect in the composite unless you blur the edges of the matte similar to the original. Fortunately software like Commotion could deal with natural motion blur so it was less of an issue. If you shot someone slightly soft in front of bright points of light (city, Las Vegas, etc) then in the edges of the blur you would have points of light that likely aren't in the new background. In these cases you may have to clamp down or paint out the offending lights.
Showing posts with label plate photography. Show all posts
Showing posts with label plate photography. Show all posts
Sunday, February 03, 2008
Tuesday, November 20, 2007
Photo Real and Realism in Visual Effects
At the start of most projects every director requests their shots be photo real
What does Photo Real mean? Are realistic vfx shots a lot more difficult than fantasy shots?
Photo Real means to create a shot that looks as real or true to life as it possibly can. It can mean that the visual effect is so totally convincing that the audience doesn’t see it. Another term for this is Invisible effects.
The lighting, textures, detail and compositing try to mimic a scene that the audience will think is real. To do this the visual effects supervisor shoots as much reference as possible when shooting the plates (live action footage that will be augmented or modified with visual effects). This may mean filmining a physical prop in the same lighting and setup. The clock in The Mask and a piece of fur for Van Helsing were photographed for the TDs (Technical Directors) to use as a look and lighting reference.
As much information is recorded at the time of photography as possible. This includes lighting diagrams, measurements of the set, camera and lens information as well as filming of the chrome and gray spheres.
All the vfx artists that work on the shot will have access to that material and be able to use it directly as well as to use it as a comparison. From this they try to create and integrate the images as much as possible.
The visual effects animator may film or obtain reference footage of people or animals moving to use as a guide, even if it’s a fictional creature.
The trouble is you may not even be creating a shot that will ever be believed.
No matter how well the animator, TD and compositor do their job if the script calls for a pink feathered whale in the sky it still won’t be considered Photo Real by the audience. There’s nothing wrong with creating shots like this since that’s the requirements for the film. The vfx artists try to add as much of real life as they can into shots like this to give it a more solid foundation. This may mean moving the whale slowly and adding in a haze layer to set the scale.
This leads to our second question regarding the difficulty of creating realistic effects.
There’s the impression that realistic effects are very difficult and much harder than shots dealing with fantasy or science fiction. Yes, realistic effects are difficult when you’re trying to create something very complex such as a held close-up of a human, moving cloth or flowing hair. But the difficulties of a shot are usually more dependent on the specific shot and less on the context of the content.
Let’s consider an effects shot: a man on crutches coming toward camera and is missing one leg. The audience will easily accept the man missing part of his leg, especially if it’s an unknown actor. The audience knows this could be real and doesn’t require a suspension of disbelief. Now consider the same shot but instead of missing the leg this man is missing his head. The headless man however doesn’t exist in real life so the audience instantly knows it not real. It will be in the back of their minds no matter how well the vfx are done. A large part of the reality of a shot is based on the perception from the viewer. From a difficulty level these are similar and use the same techniques. The headless man is probably more difficult because you have to create and track the inside of the collar.
Suspension of disbelief plays a large role in film. To some degree everything is a bit unreal in film. The basic story is a fabrication and the dialogue is hand crafted. The director of photography doesn’t necessarily match real life. He lights it to go for a specific style and to make it cinematic. Note that this can be a real problem when you’re trying to match greenscreen people with real outdoor backgrounds). Stunt people rig ramps to make cars spiral in mid-air. Not necessarily real, but certainly visually exciting (cinematic). This is the same thing with the winged spaceships and hearing explosions in the Star Wars films. Not real but cinematic.
Hopefully the story will keep the audience engaged and there will be nothing to force the audience to fixate on the effect. Anytime you give the audience a reason to suspect something, they will find it. You could have a real shot and if the audience thinks something has been added they’ll happily point out several things that are wrong with the shot. A real shot can seem fake under the certain circumstances.
People think since something exists and they know what it looks like they could certainly judge the quality. The reality is most of these effects when correctly deigned pass by audience members unless they’re very poorly done or there’s something to arouse their suspicion.
If you have a matte painting of a stylized or haunted house and center it in frame as the only thing in the shot then it’s going to be suspect. If you add a matte painting of a normal house to fill in a vacant lot on a street and then have the actors in the foreground the audience is unlikely to think about the matte painted house, especially if it doesn’t play a promenant role. Most people think a matte painting has to be super detailed but the primary issue with matte paintings is to get the lighting and perspective right.
The advantage of creating something real is you have reference of the real object or creature to constantly compare to while working on the shot. It may take a lot work to get your CG model or other items to match the real thing but you always know how close your are and where it falls short.
With imaginary shots there are frequently doubts and changes to the design since you don’t have anything to compare to. Some people think the creature should move it’s arms in one way and another group thinks it should move them in a different way. The director may switch his/her thoughts as well. A real reference gives everyone something to lock into.
If you recreate one of the NASA rocket shots now you have reference to the original material and people will accept it. They may know that you created it but it won’t remove them from the movie. If you showed the same footage 50 years ago people wouldn’t accept it as real since they had nothing to relate to.
Old movies had shots done on stage sets that were supposed to be outside. People in cars were placed in front of a rear projection screens. By today’s standards those shots don’t hold up as well because we have a different level of realism in films. It’s not that people at that time thought they were real, it’s that they accepted it much as a theater audience accepts a stage play in front of single sheet sets.
This also applies to camera moves. If you move around a model like a helicopter then the audience will accept it more than if it’s totally static from 1000 feet up or if it moves a mile in 2 seconds. The director may have wanted a photo real effect but in the effort to spice it up by moving the camera faster and further than it could in real life, you destroy the illusion of reality you had created. If you zoom out to space and then back down thousands of miles away like on Google earth then that a style decision but not one that will help the feeling of realism.
The ‘though the engine’ shots in Fast and Furious or the slit-scan shots from 2001 are pure stylized shots. They may have had a high tolerance as to what they looked like but they would still require a fair bit of effort to make work.
Some directors want to try to convince the audience that something is real by focusing on the effect and doing what they can to show it off. In the headless man shot they want the camera to fly around the man and then down through the collar to prove that there’s nothing there. This is like the magician that moves the hoops over the levitated assistant floating over the floor. But the difference is most of the time the visual effects are used to tell the story. By trying to convince the audience the shot may actually come across as more fake.
In summary, the vfx artist tries to make every shot as real as possible. In some cases that may not be possible due to the subject matter itself and in other cases may just be a style choice. Creating invisible effects is usually more dependent on the subject matter and the design of the shot than the execution difficulty.
What does Photo Real mean? Are realistic vfx shots a lot more difficult than fantasy shots?
Photo Real means to create a shot that looks as real or true to life as it possibly can. It can mean that the visual effect is so totally convincing that the audience doesn’t see it. Another term for this is Invisible effects.
The lighting, textures, detail and compositing try to mimic a scene that the audience will think is real. To do this the visual effects supervisor shoots as much reference as possible when shooting the plates (live action footage that will be augmented or modified with visual effects). This may mean filmining a physical prop in the same lighting and setup. The clock in The Mask and a piece of fur for Van Helsing were photographed for the TDs (Technical Directors) to use as a look and lighting reference.
As much information is recorded at the time of photography as possible. This includes lighting diagrams, measurements of the set, camera and lens information as well as filming of the chrome and gray spheres.
All the vfx artists that work on the shot will have access to that material and be able to use it directly as well as to use it as a comparison. From this they try to create and integrate the images as much as possible.
The visual effects animator may film or obtain reference footage of people or animals moving to use as a guide, even if it’s a fictional creature.
The trouble is you may not even be creating a shot that will ever be believed.
No matter how well the animator, TD and compositor do their job if the script calls for a pink feathered whale in the sky it still won’t be considered Photo Real by the audience. There’s nothing wrong with creating shots like this since that’s the requirements for the film. The vfx artists try to add as much of real life as they can into shots like this to give it a more solid foundation. This may mean moving the whale slowly and adding in a haze layer to set the scale.
This leads to our second question regarding the difficulty of creating realistic effects.
There’s the impression that realistic effects are very difficult and much harder than shots dealing with fantasy or science fiction. Yes, realistic effects are difficult when you’re trying to create something very complex such as a held close-up of a human, moving cloth or flowing hair. But the difficulties of a shot are usually more dependent on the specific shot and less on the context of the content.
Let’s consider an effects shot: a man on crutches coming toward camera and is missing one leg. The audience will easily accept the man missing part of his leg, especially if it’s an unknown actor. The audience knows this could be real and doesn’t require a suspension of disbelief. Now consider the same shot but instead of missing the leg this man is missing his head. The headless man however doesn’t exist in real life so the audience instantly knows it not real. It will be in the back of their minds no matter how well the vfx are done. A large part of the reality of a shot is based on the perception from the viewer. From a difficulty level these are similar and use the same techniques. The headless man is probably more difficult because you have to create and track the inside of the collar.
Suspension of disbelief plays a large role in film. To some degree everything is a bit unreal in film. The basic story is a fabrication and the dialogue is hand crafted. The director of photography doesn’t necessarily match real life. He lights it to go for a specific style and to make it cinematic. Note that this can be a real problem when you’re trying to match greenscreen people with real outdoor backgrounds). Stunt people rig ramps to make cars spiral in mid-air. Not necessarily real, but certainly visually exciting (cinematic). This is the same thing with the winged spaceships and hearing explosions in the Star Wars films. Not real but cinematic.
Hopefully the story will keep the audience engaged and there will be nothing to force the audience to fixate on the effect. Anytime you give the audience a reason to suspect something, they will find it. You could have a real shot and if the audience thinks something has been added they’ll happily point out several things that are wrong with the shot. A real shot can seem fake under the certain circumstances.
People think since something exists and they know what it looks like they could certainly judge the quality. The reality is most of these effects when correctly deigned pass by audience members unless they’re very poorly done or there’s something to arouse their suspicion.
If you have a matte painting of a stylized or haunted house and center it in frame as the only thing in the shot then it’s going to be suspect. If you add a matte painting of a normal house to fill in a vacant lot on a street and then have the actors in the foreground the audience is unlikely to think about the matte painted house, especially if it doesn’t play a promenant role. Most people think a matte painting has to be super detailed but the primary issue with matte paintings is to get the lighting and perspective right.
The advantage of creating something real is you have reference of the real object or creature to constantly compare to while working on the shot. It may take a lot work to get your CG model or other items to match the real thing but you always know how close your are and where it falls short.
With imaginary shots there are frequently doubts and changes to the design since you don’t have anything to compare to. Some people think the creature should move it’s arms in one way and another group thinks it should move them in a different way. The director may switch his/her thoughts as well. A real reference gives everyone something to lock into.
If you recreate one of the NASA rocket shots now you have reference to the original material and people will accept it. They may know that you created it but it won’t remove them from the movie. If you showed the same footage 50 years ago people wouldn’t accept it as real since they had nothing to relate to.
Old movies had shots done on stage sets that were supposed to be outside. People in cars were placed in front of a rear projection screens. By today’s standards those shots don’t hold up as well because we have a different level of realism in films. It’s not that people at that time thought they were real, it’s that they accepted it much as a theater audience accepts a stage play in front of single sheet sets.
This also applies to camera moves. If you move around a model like a helicopter then the audience will accept it more than if it’s totally static from 1000 feet up or if it moves a mile in 2 seconds. The director may have wanted a photo real effect but in the effort to spice it up by moving the camera faster and further than it could in real life, you destroy the illusion of reality you had created. If you zoom out to space and then back down thousands of miles away like on Google earth then that a style decision but not one that will help the feeling of realism.
The ‘though the engine’ shots in Fast and Furious or the slit-scan shots from 2001 are pure stylized shots. They may have had a high tolerance as to what they looked like but they would still require a fair bit of effort to make work.
Some directors want to try to convince the audience that something is real by focusing on the effect and doing what they can to show it off. In the headless man shot they want the camera to fly around the man and then down through the collar to prove that there’s nothing there. This is like the magician that moves the hoops over the levitated assistant floating over the floor. But the difference is most of the time the visual effects are used to tell the story. By trying to convince the audience the shot may actually come across as more fake.
In summary, the vfx artist tries to make every shot as real as possible. In some cases that may not be possible due to the subject matter itself and in other cases may just be a style choice. Creating invisible effects is usually more dependent on the subject matter and the design of the shot than the execution difficulty.
Monday, November 21, 2005
Filming
Filming live action for visual effects on feature films. I discuss the process of shooting on locations and sets, using references, creating interactions and things to watch for. In addition I give some suggestions of to apply this to low budget filmmaking.
I'll probably discuss moving cameras and matchmoving in the next podcast. Filming of bluescreen, minatures and other elements will be covered in future podcasts.
Transcript
In today's podcast I'll be covering the filming process relative to visual effects. First I'll focus on how it's done on a feature film and at the end I'll provide additional suggestions for filmmakers. I've actually split up this podcast so moving cameras will be discussed in the next podcast.
There are infinite possibilities when shooting a film, which is one of the reasons why visual effects are interesting. I'll be covering the basics of shooting with actors or what we term as live action. Later podcasts will discuss shooting bluescreen and miniatures.
First a review of a few terms I'll be using.
CG stands for computer graphics.
An element is an image that will be part of a composite.
A plate is a live action element.
A clean plate is a version of the shot without actors that can be used to remove any unwanted items from the real shot.
The shooting of a feature film can take two to six months. Much of the shooting depends on the project. Some projects such as Dragonheart are shot almost all outdoors, regardless of weather. This makes it like a camping trip with 2 or 300 hundred other people. Other projects may be primarily on sound stages in front of bluescreens. Most projects are a balance of exterior and stage shooting.
Prepping for the shoot
Before shooting begins it's important that the cameras are checked and prepped. This is handled by the camera assistant but for visual effects we request a steady test. When film goes through a movie camera the camera movement may cause the film to shift a bit from frame to frame. This isn't visible in a typical shot projected on the movie screen but if you composite multiple images you may well see them moving against each other. In some older movies when you watch the titles you may see them shaking against the background. This was because the original camera wasn't completely steady.
To test the steadiness a grid of white lines is applied to a black backing. This can be tape lines on a 4 by 8 foot black. This is filmed with the camera fixed on a tripod or pedestal. Depending on the test the film can be rewound and re-exposed to the same grid offset halfway by a grid space. When this is processed and projected you can see if the camera is steady and repeatable to itself. The preferred steady test is to scan the grid from the camera with your film input scanner and confirm that it's not moving relative to your control system, the input scanner.
Film live action for visual effects
The visual effects crew directly involved with the shooting is fairly small. Normally the team consists of the visual effects supervisor or a plate supervisor, 1 to 4 matchmovers, a coordinator and possibly the effects producer as well. If the show is heavy with animated creatures the animation supervisor may also be part of the team. The remainder of the visual effects crew is back at a facility working on creating CG and real models along with preparing for the full render and composite processes. The full effects crew won't start until a sequence has been shot and edited since they need to work with the footage. Because of the deadlines most shows are editing simultaneously with the shooting so finished edited sequence will be done even before the entire movie is finished being shot.
The visual effects supervisor or plate supervisor is in charge of making sure the required footage is shot correctly to do the effects later. The plate supervisor is called that since live action pieces or elements are frequently referred to as plates. A background plate for a bluescreen would be called BG plate. The matchmover position was created primarily in the digital age. It's important to be able reproduce the camera and objects exactly and that means recording all the camera information such as lens, tilt and also to measure specific items in the scene. The coordinator helps to organize all of this and to facilitate passing of information. The effects producer is normally busy at the effects house overseeing that process but the production itself may have their own effects producer on the location to help the different departments and to make sure things are moving smoothly.
Before the photography begins there's usually some pre-production at the location. Part of this is a key meeting with all the department heads, including visual effects, so everyone is clear on the requirements of each sequences and who's doing what. It's also a chance to flag any problems. Typically the storyboards and animatics are shown to the department heads and the actors so they're aware of what the final shots will look like.
Each day there is a call sheet passed out to all crew members that lists the shots/sequences for the next day as well as when each crew member is required on set. A shooting day is usually 7am to 7pm and night shooting is 6 or 7 pm to 7 am. Shooting is 5 or 6 days a week.
The setup
First thing in the morning is brief huddle of key personnel with the first asst director and director. The director has his shot list, which is the list of all shots he plans to shoot that day. For shots that require visual effects the first task is to figure out the camera position and blocking. A director may run through with the actors first to get a handle on how he wants the scene covered. For camera placement it's important to consider anything that will be added later in postproduction. I typically have a set of storyboards that have been reduced to half size so it fits in my side bag or jacket pocket. I've gone through and made notes about every element or piece of film we have to shoot for each shot and have a technique in mind for each shot. We do a quick review of the storyboard. Since the storyboard is only a guide the director or circumstances may require a change. As a visual effects supervisor I have to be able to quickly determine any implications these changes might mean. Will other elements be required? Does this change the technique? Have we already shot something else that this needs to work with? Will there be any major cost differences?
For Dragonheart I wrote some software for a powerbook that would display the dragon in the correct size on a location still, but we found it faster to take the poseable dragon model in front of the camera. With the actor standing in the scene and the physical model of the dragon we can easily check the composition and framing. I'd have a matchmover measure the distance to the actor and would calculate the scale distance for the model. If the actor was 50 feet away it might mean the model should be 23 and ½ inches away. Now the director, DP and myself would review the framing. Once the initial framing is setup we review the specific storyboard and animatic with the camera operator and actors along with key people. The practical effects and stunt crews start any rigging necessary while the director of photography lights the scene.
To help the actors and the camera operator interact with a creature we try to provide a stand in. For Dragonheart we had a monster stick that was an expandable pole with 2 disks on each side representing the eyes. For something like Mr. Hyde on Van Helsing a 2d foam core cutout was attached to a helmet worn by an actor for reference. Roger Rabbit used 2d cutouts and full-size 3d practical model. If the creature is moving someone moves the stand-in around. The actors can use the eyes as a guide where to look and react and the camera operator can make sure they provide enough room in the film frame for the creature. At least one reference is shot with this stand-in moving around. This can be used as a temp in the edit stage since the action and framing is clearer with the reference. We try to do the majority of takes without the reference to avoid having to do paint out removal of it in post. In some cases though the complexity of the action may require the stand-in be in all the takes.
Interaction
Any time you're combining multiple images you want them to blend together to make them appear to be a real scene or location. To help with this illusion we try to provide interaction of the different elements such as a creature that lifts up the actor and then swings it's tale to knock over a bookcase. This is where the special effects crew gets involved. As mentioned before technically special effects in movie credits are practical or mechanical type of effects. Normally this will have already been discussed with the special effects supervisor who will have planned and constructed some type of rig to do this. If it involves moving the actor or a stunt person then the stunt coordinator is involved. New ideas from the director at the time of the shoot require everyone to scramble to make it happen. If it was preplanned and there is an animatic we use that as a starting point for the timing of the action. If there is no animatic the animation supervisor or the visual effects supervisor is involved in working out the timing with the director. We need enough time for the actor and the imaginary creature or object to react. The asst director will usually provide a verbal cue so the special effects crew can do their part at the right time. If the creature is supposed to speak then someone on the set will be a stand-in for the creature by speaking off camera or this may come from a pre-taped voice. An actual person on the set delivering the dialog is preferred since the timing and dialog can change easily.
Another form of interaction is the lighting from the director of photography. If colored objects are supposed to emerge from a glass then the DP has to create an interactive light on the faces of the actors so when the objects are added later by the visual effects crew they look like they're creating the light effect on the faces.
Rolling film
Each shot and take is noted on the camera report and slated. For visual effects shots there are usually specific shot names or ID codes that relate to the sequence. These names may have been defined months before in pre-production and relates to specific storyboards.
The first take is usually done with any interactive reference material as monster sticks or a stand-in. After that the shots may be done without these depending on the specific requirements.
During each take the visual effects supervisor is making sure everything is working as required. Is the actor's eye line correct? Is he looking for where the creature will be in that specific moment? Has he missed a mark and put his arm through where the creature is supposed to be? Are there additional items that may need to be removed? Will the special effects rigging work and will everything look correct once the shot is finished in post? Are any cables causing a bunching up on the costumes that give away the fact the actor is on wires? Is the camera move correct and timed right? There are a hundred items to keep an eye on.
The actor's eye line becomes even more difficult when there are multiple actors. If you have a lot of extras it becomes very difficult. If you have a small object flying and hovering the illusion won't work if everyone is looking in a different direction. So to handle this you do the run through with the reference and may need to shout out timings so to choreograph this eye motion. You may need to work with the special effects people to create a small target that can be moved around that people watch. For Dragonheart we used an ultralight plane for some shots where the dragon is flying. This provides everyone with a clear idea where to look and the plane itself is removed in post.
Multiple video cameras may be mounted on tripods to provide additional reference for the animators and match movers.
I try to list on my storyboard book any additional items that may be critical to keep an eye on in a specific shot. I've also listed the additional elements that may be required.
Most of this checking involves looking at a video monitor coming from the video camera mounted in the film camera. This is known as a tap camera and unfortunately the quality of the tap cameras is about the same as surveillance cameras. The video monitor itself is at what's known as the video village. There's an operator who runs this and records video of the different takes for reference. It's around this small monitor or two that the director, script supervisor and other key people may be grouped around during a take.
If there are changes to be made the effects supervisor discusses this with the director. Normally you let the director be the one giving directions to the actors to avoid confusion.
Once the director is satisfied with the takes for the main action any additional elements are filmed. This may be the clean plate as previously discussed. This could be some practical effects such as dirt hit or an additional actor. For things like dust hits a black flat may be placed behind the dust and this element would be screened or lumikey in the final composite. If it an additional actor this may be shot against a small portable bluescreen on the location. One of the advantages of shooting these elements on the location or set is the lighting will match and camera position will match exactly. Trying to re-create sunlight months later on a stage and have it match is very difficult. The downside is this will take up more time when shooting the live action.
Once any additional elements are shot references are shot. For 3D work normally a ½ of a gray sphere is shot. This will provide a controlled reference for the technical director who lights the CG scene later. It shows where the light is coming from and the basic balance of the lights. A ½ of a chrome sphere, which may be the other side of the gray sphere, is filmed. This will provide an image for the reflection map that is wrapped around the image. This provides some of the ambient illumination as well as image for the reflection. Sometimes stills are taken with a fish eye lens to provide this same map.
A color card or grayscale may be filmed to provide a color reference. I usually try to have a reference of the object that will be added later. If we're adding a CG version of a clock such as in The Mask I'll move that through the action so the technical director, also known as TDs, can use as a guide for how the material and lighting interact. If there's a creature the model shop may provide a reference material such as section of fur if this is a creature with fur. By trying to have as many real world references as possible the final results will be based on what it would really look like in that environment. Even with fantastical creatures the aim is to make them photo real. It's actually more important to make them photo real since the eye and mind knows it's not real it tries to find any discrepancies.
So finally we have one shot done. There may be another 20 more to do that day, each with their own concerns and rigging. On a large show they may be running 2 cameras all the time to provide more angles and coverage. For complex action scenes they may be running 4 or more cameras at the same time. Any of these shots that will require visual effects will need to be watched and measured. A large film usually has second unit crew shooting additional scenes or pickups and inserts at a different location. Each of these shots has to be dealt with the same way if there are any visual effects.
On a large effects film there comes a time when the crew along with the director and assistant director start assuming that you can fix everything and they may become a bit sloppy about removing things from the scene or making final adjustments or providing you what you need. There is always pressure to keep moving on a film shoot and in some cases it will be cheaper for you to do something in post rather than taking an hour at a cost of tens of thousands of dollars to do it on location. The visual effects supervisor has to weigh these two issues and choose his battles wisely. If the quality will suffer because of production shortcuts then it's critical to flag the director and discuss the issue.
Low Budget
So how can we apply all of this to a low budget filmmaker? As always planning and preproduction are vital for keeping production moving smoothly and keeping the costs down. Make sure the effects are there to tell the story.
Try to do a rough storyboard of all your effects shots. Don't get wrapped up in created elaborate animatics or 3D storyboards. Usually the added value of these, especially for simple projects, is minimal but the time required can be enormous. It's better to put your additional time and energy into the real shot.
Analyze the different elements required to make the final shots. Remember to keep it simple. If you can do it using 2 elements instead of 5 do it with 2. List those elements with the storyboards.
Keep the storyboards with you while shooting and check off the elements as you shoot them.
Do tests ahead of time to check your technique and to determine if there are other requirements when shooting.
If this is a really low budget film you may be directing and running the camera in addition to doing the effects. This makes it even more critical to have a checklist and make sure everything is shot correctly.
Communicate with your crew so they understand what you need done. Make sure the actors understand what's required of them. The storyboards will help here.
Don't rush the shoot. If you don't get what you need or get poor quality elements then you're likely to spend a lot of time in postproduction just to create something marginal.
Be prepared. Have your tools with you. Storyboards, notepad, pens, tape measure, etc. A fanny pack or other bag is useful to hold these items.
Slate and label everything. Try being organized. When you're doing effects work you may end up with several elements for each shot. It's very easy to get overwhelmed but al l the different variations. On a feature film we have people who's focus is to keep track of all these bits.
Double-check your camera settings. If you review the footage on your video camera be sure to cue it up to after the last take. This is to avoid recording over a shot and to make sure the timecode is correct if your camera supports timecode.
Just because you can do something in post doesn't mean you should. As an example if someone left a c-stand in the shot you could paint that out later but why bother when you can just take 5 minutes and move it out before shooting. Don't try to fix everything in post. Balance the time on the location with the amount of work required and the final quality.
Keep the shots simple, especially if this is one of your first projects. Even when on set make sure you're not making things too complicated. When we were filming the The Mask we had planned a wide shot where large props are being pulled out of Jim Carrey's pants. Since this included items such as a tuba and bazooka and we saw his entire body we were going to make CG pants and stretch them to show the objects being pulled out. On the night of the shoot the director changed it to a cowboy framing, which means the bottom of the frame, is between the knees and waist. Jim's costume was a very baggy zoot suite so the stretching pants gag became un-necessary with this framing and costume. I suggested we cut the pants to make them into shorts and cut holes in the pockets. We then had two people shoving real props up into the pant pockets.
We eliminated an effects shot and had something that was better for that shot.
If you're shooting on film, especially 16mm, do steady tests before shooting or your images may jump against each other. If you're shooting film but will be finishing on video make sure the telecine is done with a solid movement. In the past you had to request a special pin registered transfer but film movements have gotten better. Just check with the video house and make sure to steady test it.
If you're shooting video try to shoot progressive if you can with a camera like the Panasonic DVX100. You can shoot visual effects with a standard video camera but the interlacing makes the process a little more difficult. Likewise if you're planning to shoot video and doing a lot of greenscreen work consider shooting on a higher end system than miniDV. You can do greenscreen with miniDV but a higher end system will provide better quality easier.
Shoot your shots as locked down cameras if possible. This will simplify most effects a lot.
Try to shoot a clean plate when possible. To make sure there's a good match you can just keep the cameras rolling and have the actors leave the scene. This avoids the chance of the camera changing or the lighting changing as the sun moves.
If you're going to purchase a composting software try to get one with motion tracking. If you're in school check on educational pricing for all software. And certainly take advantage of cameras that may be available through your school.
High quality visual effects takes a lot of time and work. Even with all the tools available nothing is as simple and easy as you would think it would be. Accept that and keep moving forward.
I'll probably discuss moving cameras and matchmoving in the next podcast. Filming of bluescreen, minatures and other elements will be covered in future podcasts.
Transcript
In today's podcast I'll be covering the filming process relative to visual effects. First I'll focus on how it's done on a feature film and at the end I'll provide additional suggestions for filmmakers. I've actually split up this podcast so moving cameras will be discussed in the next podcast.
There are infinite possibilities when shooting a film, which is one of the reasons why visual effects are interesting. I'll be covering the basics of shooting with actors or what we term as live action. Later podcasts will discuss shooting bluescreen and miniatures.
First a review of a few terms I'll be using.
CG stands for computer graphics.
An element is an image that will be part of a composite.
A plate is a live action element.
A clean plate is a version of the shot without actors that can be used to remove any unwanted items from the real shot.
The shooting of a feature film can take two to six months. Much of the shooting depends on the project. Some projects such as Dragonheart are shot almost all outdoors, regardless of weather. This makes it like a camping trip with 2 or 300 hundred other people. Other projects may be primarily on sound stages in front of bluescreens. Most projects are a balance of exterior and stage shooting.
Prepping for the shoot
Before shooting begins it's important that the cameras are checked and prepped. This is handled by the camera assistant but for visual effects we request a steady test. When film goes through a movie camera the camera movement may cause the film to shift a bit from frame to frame. This isn't visible in a typical shot projected on the movie screen but if you composite multiple images you may well see them moving against each other. In some older movies when you watch the titles you may see them shaking against the background. This was because the original camera wasn't completely steady.
To test the steadiness a grid of white lines is applied to a black backing. This can be tape lines on a 4 by 8 foot black. This is filmed with the camera fixed on a tripod or pedestal. Depending on the test the film can be rewound and re-exposed to the same grid offset halfway by a grid space. When this is processed and projected you can see if the camera is steady and repeatable to itself. The preferred steady test is to scan the grid from the camera with your film input scanner and confirm that it's not moving relative to your control system, the input scanner.
Film live action for visual effects
The visual effects crew directly involved with the shooting is fairly small. Normally the team consists of the visual effects supervisor or a plate supervisor, 1 to 4 matchmovers, a coordinator and possibly the effects producer as well. If the show is heavy with animated creatures the animation supervisor may also be part of the team. The remainder of the visual effects crew is back at a facility working on creating CG and real models along with preparing for the full render and composite processes. The full effects crew won't start until a sequence has been shot and edited since they need to work with the footage. Because of the deadlines most shows are editing simultaneously with the shooting so finished edited sequence will be done even before the entire movie is finished being shot.
The visual effects supervisor or plate supervisor is in charge of making sure the required footage is shot correctly to do the effects later. The plate supervisor is called that since live action pieces or elements are frequently referred to as plates. A background plate for a bluescreen would be called BG plate. The matchmover position was created primarily in the digital age. It's important to be able reproduce the camera and objects exactly and that means recording all the camera information such as lens, tilt and also to measure specific items in the scene. The coordinator helps to organize all of this and to facilitate passing of information. The effects producer is normally busy at the effects house overseeing that process but the production itself may have their own effects producer on the location to help the different departments and to make sure things are moving smoothly.
Before the photography begins there's usually some pre-production at the location. Part of this is a key meeting with all the department heads, including visual effects, so everyone is clear on the requirements of each sequences and who's doing what. It's also a chance to flag any problems. Typically the storyboards and animatics are shown to the department heads and the actors so they're aware of what the final shots will look like.
Each day there is a call sheet passed out to all crew members that lists the shots/sequences for the next day as well as when each crew member is required on set. A shooting day is usually 7am to 7pm and night shooting is 6 or 7 pm to 7 am. Shooting is 5 or 6 days a week.
The setup
First thing in the morning is brief huddle of key personnel with the first asst director and director. The director has his shot list, which is the list of all shots he plans to shoot that day. For shots that require visual effects the first task is to figure out the camera position and blocking. A director may run through with the actors first to get a handle on how he wants the scene covered. For camera placement it's important to consider anything that will be added later in postproduction. I typically have a set of storyboards that have been reduced to half size so it fits in my side bag or jacket pocket. I've gone through and made notes about every element or piece of film we have to shoot for each shot and have a technique in mind for each shot. We do a quick review of the storyboard. Since the storyboard is only a guide the director or circumstances may require a change. As a visual effects supervisor I have to be able to quickly determine any implications these changes might mean. Will other elements be required? Does this change the technique? Have we already shot something else that this needs to work with? Will there be any major cost differences?
For Dragonheart I wrote some software for a powerbook that would display the dragon in the correct size on a location still, but we found it faster to take the poseable dragon model in front of the camera. With the actor standing in the scene and the physical model of the dragon we can easily check the composition and framing. I'd have a matchmover measure the distance to the actor and would calculate the scale distance for the model. If the actor was 50 feet away it might mean the model should be 23 and ½ inches away. Now the director, DP and myself would review the framing. Once the initial framing is setup we review the specific storyboard and animatic with the camera operator and actors along with key people. The practical effects and stunt crews start any rigging necessary while the director of photography lights the scene.
To help the actors and the camera operator interact with a creature we try to provide a stand in. For Dragonheart we had a monster stick that was an expandable pole with 2 disks on each side representing the eyes. For something like Mr. Hyde on Van Helsing a 2d foam core cutout was attached to a helmet worn by an actor for reference. Roger Rabbit used 2d cutouts and full-size 3d practical model. If the creature is moving someone moves the stand-in around. The actors can use the eyes as a guide where to look and react and the camera operator can make sure they provide enough room in the film frame for the creature. At least one reference is shot with this stand-in moving around. This can be used as a temp in the edit stage since the action and framing is clearer with the reference. We try to do the majority of takes without the reference to avoid having to do paint out removal of it in post. In some cases though the complexity of the action may require the stand-in be in all the takes.
Interaction
Any time you're combining multiple images you want them to blend together to make them appear to be a real scene or location. To help with this illusion we try to provide interaction of the different elements such as a creature that lifts up the actor and then swings it's tale to knock over a bookcase. This is where the special effects crew gets involved. As mentioned before technically special effects in movie credits are practical or mechanical type of effects. Normally this will have already been discussed with the special effects supervisor who will have planned and constructed some type of rig to do this. If it involves moving the actor or a stunt person then the stunt coordinator is involved. New ideas from the director at the time of the shoot require everyone to scramble to make it happen. If it was preplanned and there is an animatic we use that as a starting point for the timing of the action. If there is no animatic the animation supervisor or the visual effects supervisor is involved in working out the timing with the director. We need enough time for the actor and the imaginary creature or object to react. The asst director will usually provide a verbal cue so the special effects crew can do their part at the right time. If the creature is supposed to speak then someone on the set will be a stand-in for the creature by speaking off camera or this may come from a pre-taped voice. An actual person on the set delivering the dialog is preferred since the timing and dialog can change easily.
Another form of interaction is the lighting from the director of photography. If colored objects are supposed to emerge from a glass then the DP has to create an interactive light on the faces of the actors so when the objects are added later by the visual effects crew they look like they're creating the light effect on the faces.
Rolling film
Each shot and take is noted on the camera report and slated. For visual effects shots there are usually specific shot names or ID codes that relate to the sequence. These names may have been defined months before in pre-production and relates to specific storyboards.
The first take is usually done with any interactive reference material as monster sticks or a stand-in. After that the shots may be done without these depending on the specific requirements.
During each take the visual effects supervisor is making sure everything is working as required. Is the actor's eye line correct? Is he looking for where the creature will be in that specific moment? Has he missed a mark and put his arm through where the creature is supposed to be? Are there additional items that may need to be removed? Will the special effects rigging work and will everything look correct once the shot is finished in post? Are any cables causing a bunching up on the costumes that give away the fact the actor is on wires? Is the camera move correct and timed right? There are a hundred items to keep an eye on.
The actor's eye line becomes even more difficult when there are multiple actors. If you have a lot of extras it becomes very difficult. If you have a small object flying and hovering the illusion won't work if everyone is looking in a different direction. So to handle this you do the run through with the reference and may need to shout out timings so to choreograph this eye motion. You may need to work with the special effects people to create a small target that can be moved around that people watch. For Dragonheart we used an ultralight plane for some shots where the dragon is flying. This provides everyone with a clear idea where to look and the plane itself is removed in post.
Multiple video cameras may be mounted on tripods to provide additional reference for the animators and match movers.
I try to list on my storyboard book any additional items that may be critical to keep an eye on in a specific shot. I've also listed the additional elements that may be required.
Most of this checking involves looking at a video monitor coming from the video camera mounted in the film camera. This is known as a tap camera and unfortunately the quality of the tap cameras is about the same as surveillance cameras. The video monitor itself is at what's known as the video village. There's an operator who runs this and records video of the different takes for reference. It's around this small monitor or two that the director, script supervisor and other key people may be grouped around during a take.
If there are changes to be made the effects supervisor discusses this with the director. Normally you let the director be the one giving directions to the actors to avoid confusion.
Once the director is satisfied with the takes for the main action any additional elements are filmed. This may be the clean plate as previously discussed. This could be some practical effects such as dirt hit or an additional actor. For things like dust hits a black flat may be placed behind the dust and this element would be screened or lumikey in the final composite. If it an additional actor this may be shot against a small portable bluescreen on the location. One of the advantages of shooting these elements on the location or set is the lighting will match and camera position will match exactly. Trying to re-create sunlight months later on a stage and have it match is very difficult. The downside is this will take up more time when shooting the live action.
Once any additional elements are shot references are shot. For 3D work normally a ½ of a gray sphere is shot. This will provide a controlled reference for the technical director who lights the CG scene later. It shows where the light is coming from and the basic balance of the lights. A ½ of a chrome sphere, which may be the other side of the gray sphere, is filmed. This will provide an image for the reflection map that is wrapped around the image. This provides some of the ambient illumination as well as image for the reflection. Sometimes stills are taken with a fish eye lens to provide this same map.
A color card or grayscale may be filmed to provide a color reference. I usually try to have a reference of the object that will be added later. If we're adding a CG version of a clock such as in The Mask I'll move that through the action so the technical director, also known as TDs, can use as a guide for how the material and lighting interact. If there's a creature the model shop may provide a reference material such as section of fur if this is a creature with fur. By trying to have as many real world references as possible the final results will be based on what it would really look like in that environment. Even with fantastical creatures the aim is to make them photo real. It's actually more important to make them photo real since the eye and mind knows it's not real it tries to find any discrepancies.
So finally we have one shot done. There may be another 20 more to do that day, each with their own concerns and rigging. On a large show they may be running 2 cameras all the time to provide more angles and coverage. For complex action scenes they may be running 4 or more cameras at the same time. Any of these shots that will require visual effects will need to be watched and measured. A large film usually has second unit crew shooting additional scenes or pickups and inserts at a different location. Each of these shots has to be dealt with the same way if there are any visual effects.
On a large effects film there comes a time when the crew along with the director and assistant director start assuming that you can fix everything and they may become a bit sloppy about removing things from the scene or making final adjustments or providing you what you need. There is always pressure to keep moving on a film shoot and in some cases it will be cheaper for you to do something in post rather than taking an hour at a cost of tens of thousands of dollars to do it on location. The visual effects supervisor has to weigh these two issues and choose his battles wisely. If the quality will suffer because of production shortcuts then it's critical to flag the director and discuss the issue.
Low Budget
So how can we apply all of this to a low budget filmmaker? As always planning and preproduction are vital for keeping production moving smoothly and keeping the costs down. Make sure the effects are there to tell the story.
Try to do a rough storyboard of all your effects shots. Don't get wrapped up in created elaborate animatics or 3D storyboards. Usually the added value of these, especially for simple projects, is minimal but the time required can be enormous. It's better to put your additional time and energy into the real shot.
Analyze the different elements required to make the final shots. Remember to keep it simple. If you can do it using 2 elements instead of 5 do it with 2. List those elements with the storyboards.
Keep the storyboards with you while shooting and check off the elements as you shoot them.
Do tests ahead of time to check your technique and to determine if there are other requirements when shooting.
If this is a really low budget film you may be directing and running the camera in addition to doing the effects. This makes it even more critical to have a checklist and make sure everything is shot correctly.
Communicate with your crew so they understand what you need done. Make sure the actors understand what's required of them. The storyboards will help here.
Don't rush the shoot. If you don't get what you need or get poor quality elements then you're likely to spend a lot of time in postproduction just to create something marginal.
Be prepared. Have your tools with you. Storyboards, notepad, pens, tape measure, etc. A fanny pack or other bag is useful to hold these items.
Slate and label everything. Try being organized. When you're doing effects work you may end up with several elements for each shot. It's very easy to get overwhelmed but al l the different variations. On a feature film we have people who's focus is to keep track of all these bits.
Double-check your camera settings. If you review the footage on your video camera be sure to cue it up to after the last take. This is to avoid recording over a shot and to make sure the timecode is correct if your camera supports timecode.
Just because you can do something in post doesn't mean you should. As an example if someone left a c-stand in the shot you could paint that out later but why bother when you can just take 5 minutes and move it out before shooting. Don't try to fix everything in post. Balance the time on the location with the amount of work required and the final quality.
Keep the shots simple, especially if this is one of your first projects. Even when on set make sure you're not making things too complicated. When we were filming the The Mask we had planned a wide shot where large props are being pulled out of Jim Carrey's pants. Since this included items such as a tuba and bazooka and we saw his entire body we were going to make CG pants and stretch them to show the objects being pulled out. On the night of the shoot the director changed it to a cowboy framing, which means the bottom of the frame, is between the knees and waist. Jim's costume was a very baggy zoot suite so the stretching pants gag became un-necessary with this framing and costume. I suggested we cut the pants to make them into shorts and cut holes in the pockets. We then had two people shoving real props up into the pant pockets.
We eliminated an effects shot and had something that was better for that shot.
If you're shooting on film, especially 16mm, do steady tests before shooting or your images may jump against each other. If you're shooting film but will be finishing on video make sure the telecine is done with a solid movement. In the past you had to request a special pin registered transfer but film movements have gotten better. Just check with the video house and make sure to steady test it.
If you're shooting video try to shoot progressive if you can with a camera like the Panasonic DVX100. You can shoot visual effects with a standard video camera but the interlacing makes the process a little more difficult. Likewise if you're planning to shoot video and doing a lot of greenscreen work consider shooting on a higher end system than miniDV. You can do greenscreen with miniDV but a higher end system will provide better quality easier.
Shoot your shots as locked down cameras if possible. This will simplify most effects a lot.
Try to shoot a clean plate when possible. To make sure there's a good match you can just keep the cameras rolling and have the actors leave the scene. This avoids the chance of the camera changing or the lighting changing as the sun moves.
If you're going to purchase a composting software try to get one with motion tracking. If you're in school check on educational pricing for all software. And certainly take advantage of cameras that may be available through your school.
High quality visual effects takes a lot of time and work. Even with all the tools available nothing is as simple and easy as you would think it would be. Accept that and keep moving forward.
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