The question: This
may be tricky for people who have only Maya 3D skills and no
photography knowledge to answer. A "standard lens" is a focal length
which for a given size of film plane (or sensor) will neither widen nor
magnify the image it captures. For example, a 50 mm lens on a full
frame 35mm sensor is considered a standard lens.
perspectives can be matched using Maya 3D camera options, but what is
the default equivalent of the sensor size in the program? My reply: Indeed,
many artists with no experience in photography will not be able to
easily understand the relationships between focal length and sensor
sizes / ratios.
Having worked in the "camera department" on
Hollywood films, it has given me great insight into the relationships
between the physical camera and the virtual one in Maya.
does not make it easier. What we know in the VFX/Film world as "sensor
size" / "film back" / "film format", is known in Maya as "Camera
Aperture". This attribute is found in any Maya camera's shape node. In
the attribute editor under the Film Back section you will see: Film
Gate, Camera Aperture, Film Aspect Ratio, and Lens Squeeze Ratio.
Just like you said there is a relationship between focal length and the sensor size.
in the Attribute Editor for the Maya camera, the way we get the correct
sensor size or film format for our camera gate is to set the Film Gate
attribute to "35mm Full Aperture". This is actually a preset that sets
the "Camera Aperture" attribute to 0.980 x 0.735.
From the Wikipedia page for Super 35
film formats of printed film strips, (4th para), I quote "If using
4-perf, the Super 35 camera aperture is 24.89 mm × 18.66 mm (0.980 in ×
That is exactly what Maya is giving us (in inches, which is frustrating, when we are describing 35mm in millimeters).
the same Wiki article we also learn of the film dimensions of 35mm
Academy format which is 21.95 mm × 16.00 mm (0.864 in × 0.630 in). That
is what the Maya Film Gate preset gives us if we switch to 35mm
However, we are not limited to only the presets found in
the Film Gate attributes. Knowing that Maya is just filling in
measurement of the film back dimensions now enables us to input
measurements from our own camera sensors even if their measurements are
In this context, whatever focal length that you now
set, will give you the actual framing of a real world camera with the
same sensor size / film back.
We do all these, to make sure that the numbers will all make sense: the dimensions of the sensor size and the focal length.
forward, we are faced with 2 settings, and two different framings when
you look at the viewport: one is our camera's film back / sensor ratio,
and the render resolution. Maya gives us the flexibility to have both.
it becomes wildly confusing if we do not know what we are doing.
Without guides we will never know which object that is displayed in our
viewport is going to get inside the rendered frame eventually. Even when
you render, you are only seeing the framing of your render resolution,
not the framing of your film gate.
Here is my standard workflow, so we see the edges of my resolution and my film gate. I do this for all my render cameras:
In the Camera's attribute editor: - set "Fit Resolution Gate" to "Overscan", under display options section - turn on "display film gate". This displays our film back /sensor boundary - turn on "display resolution". This displays our rendering resolution boundary - turn off "display gate mask" - set "overscan" to 1.05 (I like to be able to see a bit more beyond my frame)
these will make sure you see 2 boundary boxes, one with a solid line,
and the other one, drawn with a dotted line. The dotted box defines the
film gate / sensor bounds, and the solid box defines your rendering
boundary, defining the resolution of your rendered image.
aspect ratio of your film back and your render output resolution is the
same, you will see only 1 set of framing guide. That is because both are
drawn on top of each other. At this point we have successfully matched
our film gate and resolution gate.
At this point our Maya camera's focal length will reflect that of the camera's real-world counterpart.
this is only part of the story. In order for our camera's framing in
Maya and the real world to match, the scale of the CG objects and the
distances in your scene must now be consistent with the real world. That
is to say, if I want to find out what a 50mm lens would see and frame,
for a subject that is 1.8 meters tall, standing 2 meters away, in the
real world, I would need a CG character that is modelled to be 1.8
meters tall in scale, and placed 1.8 meters from the Maya camera in the
If any of these are off scale, our measurements will
become inaccurate, and all our calculations with the camera will end up
as inaccurate framing once again.
In many aspects of film VFX
production, CG elements need to integrate with live plates. Thus, the
creating and laying out of assets in the right scale for a scene is
critical. This is especially so in the camera tracking, simulation
(water, smoke, cloth, fire, muscles) , and lighting departments.
distances and scaling are not accurate, camera framing or surveyed
measurments on the phsyical filming set will not be able to match up
with the CG camera set-up in Maya.
In the lighting part of the
workflow, light intensity will not be accurate, and light energy falling
off across distances will become too slow or become too fast.
In simulation and dynamics, inaccurate scaling will cause forces to be either too weak or too strong, and thus unnatural.
a production is fully CG, the matching of cameras' framing to their
real world counterparts become less critical. But there will still be
directors who strive for that extra bit of believability in their
framing and camera work. So it is still a desirable skill to have for
any CG artist that has to handle a CG camera.