[ I posted some of this on the 2001: A Space Odyssey 35mm Preservation (Help Needed - original 1968 prints obtained), but moved it here where it belonged ]
In the other thread, an observation came up on 2001's use of front projection. This article illuminates:
American Cinematographer: Front Projection for 2001: A Space Odyssey, by Herb A. Lightman wrote:
The surfacing material used for the giant screen was a special 3M fabric coated with very tiny mirrored beads of glass. … This special lenticular 3M material comes in rolls and an effort was made to surface the screen by mounting it in 100-foot strips. However, because of a slight variation in reflectivity between rolls, seams were frequently visible under projected light. An attempt to match strips exactly proved unsuccessful, so the material was finally torn into small, jagged, irregular shapes which were mounted in a “camouflage” mosaic, shape on top of shape, so that there was no longer any visible variation in reflectivity.
While examining such a shot in a Dawn Of Man sequence (specifically the sky area, which looked patched & tattered), I was reminded of something else I noticed long ago – the set and the projection didn’t blend very well. Naturally, I tried a quick fix. Masking off all of the projected area (an easy task to clearly see the color-difference boundary), the set was color corrected to match the projection. (It could have been corrected the other way around, but this was just a proof-of-concept.) The result was amazing! Suddenly it looked like an on-location shoot that went all the way to the horizon, just as they originally wanted.
TOP is the original Blu-ray screenshot, BOTTOM is the projection-masked-off color correction . .
Doing that reminded me what I noticed more recently – something that looked like an anamorphic-lens brightness roll-off, where the edges of the picture darkened in curvature. Again, a quick fix, to make a mask that would brighten the picture ever more towards the edges. A square gradient from black-to-white was made, pasted back against itself for white-to-black-to-white, and then stretched to fit the picture size . .
Next, to apply the proper lightening, the mask’s histogram was adjusted to produce no lightening effect in the center but to sharply increase it’s lightening towards the edges . .
In a paint program, this mask was layered onto the picture and specified as a “dodge” mask, to increase the exposure as mask-areas increased from dark to light . .
The result was excellent (even though the picture still needs more rounded illumination into the corners)!
TOP is the color-corrected picture, BOTTOM is the luminance compensation . .
So, could something like this be applied throughout the film (it all looked like roll-off)? With another screenshot, bright instead of dark, colorful instead of earth-tones, I tested it but it was too much. By adjusting the mask layer’s transparency to limit the effect (50% seemed about right), the noticeably dimmer walls at the edges now became more like the brightness of the walls in center screen (BTW, no color correction this time, just the luminance test) . .
More fixes for 2001: A Space Odyssey. (Forgive me, Stan, forgive me!) 😄