Knowledge about your camera is essential when dealing with live action footage/photography that will eventually be mixed with CG elements.
Firstly let’s mark this website down: www.dpreview.com. It shows every specification of a camera that we will need when trying to mimic the camera in CG. Let’s go through the essential terms now.
Aperture & F-stop: Amount of light allowed into lens.
Up one stop means twice as small of aperture and thus less light. Pinhole camera is like F22. Depth-of-field is a direct result of changing the aperture size, where lower F-stop translates into a narrower DOF. Usually for VFX we want high F-stop/small aperture so the picture is sharp any lens flare is reduced in size and less vignetting.
Shutter Speed/Exposure: Amount of time it takes for the shutter to open and let light fall on the CCD.
If we are using handheld or longer lens, we might try to reduce the exposure time / use faster shutter speed to reduce motion blur. But try to always use a tripod when doing VFX! Especially at night, we need longer exposure.
Sensitivity/ISO: How sensitive the CCD is.
Lowest ISO is desirable for VFX as it produces less grains.
Focal Length: A measurement on the lens related to focus of light.
Wide angle lens as more depth of field and thus more desirable in VFX. There are various focal length, such as 28mm, 35mm etc. It depends on the shot. Don’t forget to adjust the focus of the lens as well.
Light bounce settings also play a part. We could use incandescence and florescent settings to get the right color for lights in a shot, and sometimes we could stitch both to get the most accurate results.
So in summary, small aperture size and low ISO are desirable when trying to get as much information from a live action reference as possible!
A small exercise involving greenscreen capture, motion tracking and compositing in nuke!
I was approached by Hong Cheng, my fellow ADMer from film major to do a VFX shot of spaceships over the Singapore skyline at night. It will be composited over a square TV screen, and the design of the ship will be done by my other fellow film ADMer Russell Chen.
Here’s the work done within a tight deadline. We filmed the footage and took pictures of a chrome ball (for lighting) on location for about 2 hours that night. Then I took half a day to model and texture/light, another half to settle the light fogs and composition, and another day of compositing and tracking.
Not all that good but I guess I learned enough to be able to do more decent job next time!