We bought a 35mm DOF adapter last month, and put it through some rigorous tests to see if it could help out with the Arcturus System filming.
Of course, most of what we shot for testing had nothing to do with the movie, just the standard tests. We were mainly looking for things that would affect chroma-keying. We found several problems:
1) Very dark corners.
2) Chromatic Aberration (ie, color shift).
3) Barrel distortion (makes the picture look like it is being shot with a very wide-angle lens).
The dark corners will affect the keying the most - it creates a problem, because you want even lighting across the canvas. A dark corner means much more work, or makes a shot completely unable to be keyed.
The chromatic aberration shifts to violet in certain areas. This creates an issue, because we’re shooting in front of a blue screen (violet and blue are very similar). It means that the key would again be affected.
The barrel distortion I could actually live with. David Crosson (the DP) and I both agree that it could give the film a “tighter” feel. But, the fact that we can only have barrel distortion doesn’t bode well with me.
Here’s some pics:
This is my step-son, Nick. See the blue/violet color shift on his back (arrows point to it - it may be hard to see, since I had to shrink the pictures down to fit the site).
See the dark corners?
Don’t really notice any dark corners in this shot. You may see a lot of grain because I didn’t have the vibrating ground glass “on” (nor was the GG cleaned). Kinda cloudy day. Not a bad picture.
I think this shot shows off how well one of these adapters works. Not sure if you can notice the colors shift on the electric pole (upper left) and on his blue pants though. There’s also a slight tint of blue on the upper right side of his shirt and the back of his neck (most of the visual detail was lost when shrinking these pics).
Shows the “warping” of the image. Not horrible, but bad enough for me. Also, notice the blue shift again? Left of the car? On the white windows? The grass is overexposed because I was trying to film Nick in the shadow of the barn.
Notice the dark corners?
You see a little barrel distortion and color shift in this one as well.
Some of the above grain issues may be due to compression, or possibly due to de-interlacing, but my overall opinion is that the pics stand for themselves enough to make an educated guess as to what this particular 35mm adapter will do. I didn’t have the ground glass on vibrate in most of these shots, nor had I cleaned the ground glass, so try to overlook the more grain. Also, it was all handheld, so some of the shots may not be completely in focus.
All was shot with a Canon 50mm FD mount lens and the Z1U. I did raise the shutter speed on a bunch of the shots to very high (2000 to 4000+) to keep the Sunlight under control. I’m not sure if this effected the setup or not. I also used the Canon lens to control the light as well. No ND filters were used at anytime - neither in camera, nor in front of the lens.
In separate tests, I did put a few 72mm filter rings between the rig and the camera, trying to extend the adapter from the camera to try and take out the barrel distortion, also hoping it would help the dark corner issue, but to no avail. It just didn’t work. I could possibly move the ground glass forward (away from the camera) to see what that will do, but for some reason, I think I’ll be re-inventing the entire adapter.
For chroma keying work, I don’t feel it can be used effectively, although I did not try it in front of the blue screen. The color shift looks like it will create a major problem for chroma keying, as well as the much darker corners will especially have issue.
