Shooting on Set
It’s always best to place the foreground elements as far away as possible to avoid this bounced light from reaching them.
If you’re shooting a night-time scene, a blue screen may prove a better choice since any unwanted contamination on the subject is more forgivable in hair or skin tones at night. Cool tones dominate night-time shots, but of course you may have to light the screen with more illumination than a green screen.
Everything else can be taken care of quickly with either garbage or hold-out mattes, but obtaining a quality edge will require the lions-share of your time.
Of course it goes without saying that you want to shoot with the highest special resolution possible in order to minimize the issue of noise or grain, and to capture the cleanest and least-clipped information as possible. I like to shoot in the RAW color space as opposed to encoding straight to a RGB colorspace in case you need to drastically and temporarily color correct the footage to get a good key (particularly in low light situations). More information on colorspaces in another article coming soon (linear, logarithmic, ProPhoto, Adobe RGB, Rec. 709 and sRGB)!
Having a reference photo or concept art planned out will be a great help for matching the direction, intensity and quality of the foreground lighting to what will eventually be the background plate or element in the composite. Although a degree of relighting is possible in compositing packages, it’s always best to make sure you get the lighting correct in the photography stage to save many long hours of fixes.
Analyze the direction of the shadows in the background plate and line up your key light to match, and try to duplicate the indirect bounce light with your on-set fill light. Matching color temperature is as important in the fill as it is in the key light, so use colored gels if needed. It’s important to get as close as you can on-set, and only need to tweak the color temperature and intensity in post. A rim, or back light, is usually reserved for shots that give a studio-like look, and can detract from the realism of a true photographic composite. Consider adding more fill lights instead of a strong rim unless there is a definite background source of light in the composite scene.
Very common in the motion-picture industry is the practice of shooting on set with the additional benefit of the Ultimatte real-time hardware system. This proves an incredible assistance in lining up lights, intensities and shadows while the video assist monitor will show a close approximation of the final comp.
Of course, you don’t want to record the Ultimate combined-composite for your plates, since this negates the color screen in the plate and destroys the ability to further adjust the foreground elements in post-production.
If your digital camera has any built-in sharpening or ‘image enhancement’ features, you should take care to turn all this off! If you’re using a quality lens, there’s no need for digital enhancement features that do little more than add noise and artifacts to the image. Remember, you can never really digitally sharpen an image – you only add contrast to the bordering pixels.
Keep your shutter speed fast enough so you don’t record unnecessarily-long motion blur. Excessive motion blur creates more work for you and the keying software. If you need to sweeten up the motion blur in post, you can add optical flow analysis nodes in Nuke or the very popular ReelSmart Motion Blur.