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You often/used to hear that "35mm film is 4K, 16mm film is 2K, and Super 8 film is 720p," so why do I often see services such as this one offering to digitize Super 8 film at 4K?

If all of the information on a Super 8 film has already been captured at 720/1080p then what's the point of digitizing the film at higher resolutions such as 4K?

I realize that when a 4K display receives a 1080p input that the display will have to upscale the picture using methods such as interpolation. But if one were to output a Super 8 film at 4K resolution to be displayed on a 4K display, wouldn't you be filling the 4K display with empty pixels given that all of the information on the Super 8 film has already been captured at 720/1080p?

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  • Are you talking real super-8 film, as in silver-based emulsion? Or a digital "super 8" format? For film, the highest digital capture resolution should be used (for the highest quality reproduction); film in general is higher "resolution" because its images are formed from microscopic silver grains. For digital video, of course, there would be no reason for digitizing at all. Commented Mar 11, 2021 at 15:04
  • @user8356 Not sure what you mean by silver-based emulsion, I mean I know what an emulsion is, but I grew up entirely in the digital era, so these terms predate my time. When I say Super 8 film, I mean analog Super 8 film reels from the 70's. Are you saying 4K still makes sense for Super 8 film? If it does, then I'm not sure what I should do, since I couldn't find any Super 8 film converters that can output in 4K, that would allow me to do it myself. There are services which use specialized machine that can output in 4K, but they are expensive. What do you suggest I should do? Commented Mar 11, 2021 at 19:27
  • @user8356 ...Save up to have someone do it for me, or purchase a converter that can output in 1080p and do it myself? Commented Mar 11, 2021 at 19:32
  • @user8356 Services, such as this one, offer to digitize Super 8 film at 4K, but they charge $0.90/foot. If I do some simple math, 33 3-in reels at 50 feet of film per reel times $0.90/foot = 33 x 50 x 0.90 = $1485 vs. buying a converter from an established company that can only output in 1080p for $299.95 such as this one. What do you suggest I do? Save up to have it done for me in 4K or get a converter that can only output in 1080p and do it mys Commented Mar 11, 2021 at 19:54
  • When you digitize an analog source, the highest resolution is usually best. However, as you show, the cost of 4K digitization is too high. There is nothing wrong with digitizing at 1080p. It should look good on a large monitor or TV, and file sizes won't be as huge as 4K. Also, the original focus and exposure of the film might not be that good, so no need to use 4K for quality that isn't there. You could have a pro service digitize a real at 1080p so you can compare their results to the quality you get doing it yourself. I do not know if home film digitizer will produce good 1080p results. Commented Mar 12, 2021 at 15:27

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Calling super-8 720p is confusing. There are no rows of pixels, only grains of emulsion, scattered in a random pattern on the base.

That said, film does have an upper bound on its resolving power, in other words, the smallest detail it can reproduce. Kodachrome could resolve 96-135 lines per millimeter, which can be roughly converted to 180-270 pixels per mm (it takes two pixels to resolve a line). A super-8 frame is 3.3mm high, so the vertical resolution is somewhere between 540 and 810 pixels. So as a back-of the envelope description of its resolving power 720p is a good approximation.

So if you capture super-8 in HD you will be getting enough resolution in your digital file that all of the image that is present on the super-8 frame will be preserved. Higher resolution will just give you more detail of the grain. It won't look worse, but it won't look a whole lot better.

What I would be more concerned about was the fidelity of the colour, and the quality of the transfer. A well transferred, lower resolution transfer will beat a poorly done higher resolution transfer any day. You can just project the film on a wall and film it, but it's probably going to look dreadful.

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  • Thanks for taking a stab at answering the question. I didn't think anybody would and only noticed now that you answered the question, although I was able to glean some useful information from just the comments. My question, though, wasn't just about digitizing analog Super 8 film, it was also about the whole point of outputting an analog source at higher resolutions in general, i.e. scanning an analog photograph or digitizing Super 8 film. Commented Mar 31, 2021 at 19:24
  • Specifically, why does outputting an analog source at higher resolutions produce a better picture quality, however slight, on higher resolution screens than just outputting at a lower resolution and letting the higher resolution screen fill in the pixels using interpolation? That was really the question I needed to have answered. Commented Mar 31, 2021 at 19:25
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    A 4k scan will probably look better on a 4k screen than a 1080p scan digitally up-scaled. The extra resolution will be coming from the source, rather than an interpolation algorithm. But it will just be more detailed globs of grain, rather than actual image. Commented Apr 2, 2021 at 1:16

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