As to what other camera settings I use, for consistency with the “film look” I’ve shot everything in 24PA to match the other footage. Also, I figure it saves 6 frames of rendering per second when I go to composite.
Now, on the HVX you can turn on a targeted brightness setting that displays the percent brightness on the LCD. I don't recall at the moment if the DVX has this feature. [Editor's Note: The DVX doesn't appear to. However, readers can get around this if they have dvRack or if they have Adobe's OnLocation CS3, which is part of the PC version of CS3: Production Premium.]
Anyway, I turn on only the backdrop illumination and then zoom in a bit and pan the wall. This enables me to read the brightness on the backdrop at various locations rather than try to get it evenly lit by eyeball. What I found is that the eye is so adapted to changing the size of the iris for different brightness that my eyes will change as I look across the backdrop and will fool me into thinking things are evenly lit that are way off. Using the camera as kind of a light meter I can see if part of the backdrop is 46% bright or only 40% bright – and that makes a difference in the composite. So I set the lights, move them and change their distance and angle from the backdrop using the camera values to guide me.
Often my checklist for shooting with the HVX (or DVX) is:
1. Get the lighting even on your background first.
2. Turn off the background lights and turn on the foreground lights and do a white balance.
3. Then use the auto iris to check the backround brightness and the foreground brightness.
I play with the foreground lighting to try to get the subject a full stop brighter than the background so there is better luma separation and less spill. Then I fix the iris setting before turning on the background lights. Overall, the images that I get are slightly blown out in the background because the iris was set without the background lights on. And sometimes I manually adjust the exposure a bit. The foreground has too much red in the skin tones, maybe because I'm shooting in a fairly green room without a lot of distance between the subject and the background. So there might be ambient bounce even with the backdrop lights turned off that gives me a slightly greenish white balance.
In post, if you're using Keylight, remember to apply a 2.5 pixel edge pre-blur to the SD footage from the DVX100 and a 1 to 1.5 pixel preblur on the HD footage from the HVX200. (Since the 4:1:1 color space of the DVX100 and the 4:2:2 color space of the HVX200 tend to leave artifacts in Keylight, the preblur smooths out these issues. For more information on how color space works, check out our article on the Basics of Chromakey Compositing and Rules to Shoot By.) I learned the preblur trick from Andrew Kramer's Serious Effects & Compositing DVD. If you don't have it, you should get it. Because what it teaches you to do in AE compositing is almost impossible to invent. (Or it was for me, anyway).
Now that I have the HVX, I shoot in 1080/24P. That’s an interlaced format. So I use CinemaTools to reverse the Telecine. Then I down-size to 720P. Most compositing then happens at 720. But for a scene with “high frequency details” like hair — I’ll go to 1080 for the composite and then reduce the result to 720p after the composite. I ran side-by-side tests of an actor with long light colored hair “fluffing” it out with her hands. I then composited this image on a bright beach background. The 1080 and the 720 both looked very good, owing to the 4:2:2 color sampling. The only thing that appeared differently was the detail in the hair where the background showed through. In the 720 image it was more of a blur. In 1080 the hair details still showed through. And this held up after composite when the 1080 was reduced to 720.
I overlaid two 720 size stills in Photoshop and used the “difference” blending mode so that I could see where the additional detail was showing up using the different workflows. 1080 rendering takes longer. So I pick and choose when I’m going to use it. But it’s nice to have the option.
Hopefully this information will help you as you work to obtain better greenscreen results with your DVX100 and HVX200 cameras!
