[tagoregrtst]

Film development is very non linear in the exposure (call it z dimension), not in the dimension (x and y). That is to say it might exaggerate or diminish a gradient that was already there but not create one from nothing.

The grain is random size and randomly distributed which cancels out a lot of the effects of discritzation (eg you wont get patterns due nyquist sampling error).

[sudosysgen]

It's non linear in the X and y dimension because of grain.

Any camera with a good antialiasing filter will also have little to no discretisation error.

[tagoregrtst]

Its non linear because enlarger optics are non linear.

The image of a digital or a film photo is a mosaic. This mosaic can be mathematically enlarged into a large mosaic. If you enlarge far enough you’ll see the individual tiles. This is a linear operation no matter the shape of the tile.

Digital photos do not, however, just make the tiles larger. They could but its not done.

Even before enlarging, they interpolate between tiles to recover color (each pixel in the sensor is monochromatic).

When a picture is displayed, the screen resolution is not that of the photo, so an algorithm has to fit one grid into another. And this is before going into superesoltion techniques.

But none of this would matter if we had a standard, open source, way to utilize digital photos in court. Until then Mr. lawyer can get himself an expert to testify to the validity of each and every still he wants to show the court.

[sudosysgen]

Actually, it's not a superresolution situation. Normally, the resolution of the sensor is higher than that of the screen.

The algorithm used when zooming in a video on any platform I know about is no different as far as distorting as enlarging optics. They are moreso interpolation algorithms than superresolution algorithms.