I may be incorrect, but I've heard varying reports that film holds a resolution of almost 8K.
It can, but it depends on what the gauge of the film is, what size aperture is used and what sensitivity or speed (ISO number) the film is. Slower speed film has less visible grain and looks cleaner and sharper. Fuji used to make this really great daylight slide film called Velvia 50 that photographers loved to use partly due to its exceptional sharpness and high resolving power. According to Fuji themselves
, Velvia 50 had a resolving power of 160 lines per millimeter. If you apply that as an upper limit to the most commonly used motion picture film formats, you get numbers like these:
- 4-perf 35mm, Full Aperture (aka Super-35): 3987 x 2987 - 4K
- 8-perf 35mm, Full Aperture (aka VistaVision): 6075 x 4027 - 6K
- 5-perf 65mm, Full Aperture (aka Super Panavision): 8421 x 3682 - 8.4K
- 15-perf 65mm, Full Aperture (aka IMAX): 11,266 x 8421 - 11.3K
Again, that would be the upper limit
of what the original camera negatives would be capable of. The printing process obviously makes the image softer and grainier every time a copy is made, from negative to interpositive, then internegative to release print (a third generation copy). By that point you only have around 90 lines per millimeter of resolving power. So, for the two primary 35mm print formats:
- Flat 1.85:1 prints: 1886 x 1020
- Scope 2.35:1 prints (before 2x stretch): 1886 x 1578
The actual perceivable resolution in the theater would be even lower, however, due to the mechanical motion of the film through the projector (gate weave), the edge-to-edge sharpness quality of the lens and brightness of the lamp. In subjective assessment tests using resolution charts, the sharpest part of the screen (not always the center) is usually reported to be between 875-750 lines per picture height for a 1.85:1 image. The average sharpness all over can be as low as 685 lines!
We should all be very, very grateful for digital projection. Even lowly 2K projection!