Is scanning 16mm at 4K/5K too much?

Discussion in 'Film and Processing' started by johngoodman, Jul 1, 2017.

  1. I hear people claim that 16mm is no larger than 2K in resolution. So is having it scanned at a higher resolution overkill?
     
  2. I think so, yes. Having shot Agfapan 25 in a Minox (approximately the same negative size) I didn't really discover resolution for prints at 5x7". If you don't need a multitude of pixels per film grain to write your PhD thesis about grain shapes and structures or to include the crappy old footage as a stylish element into a 4 or 5K movie a 4K scan would be most likely absolute overkill. 4K from 35mm footage might already be a stretch.
     
  3. From experience in other formats, I can see grain on most film stocks at 3200 dpi.

    A 16mm movie frame is .4"x .3". At 3200 DPI, that's roughly 1000x1200 pixels, or 1/4 the number of vertical pixels in 4K.

    So, I'll say that yes, it is a waste.
     
  4. If you sell hard drives, online storage, and scanning services, it's not nearly enough.
     
    johngoodman likes this.
  5. You can always down size from a high resolution scan and have a good image but you cannot upsize from a low resolution scan and get a good image.
    Let your planned usage determine the size not others opinions.
     
    Wilmarco Imaging likes this.
  6. There is some truth to that, but at the same time if all scanning in 4K gets you is bigger pictures of the grain(or dye clouds) you're just putting in more time and effort for no real-world gain in resolution.
     
  7. Does this mean people that offer high scans for 8mm and 16mm are basically conning people?
     
  8. I agree with thirteenthumbs: scan at a higher resolution than you need, then scale down. This is how it should be done where possible. A lot of people are used to looking at photo scanners which often exaggerate grain, giving the illusion that resolving power is not very high. Cinema scanners don't exaggerate grain, and they should be referred to when talking about movie film. Some would be surprised at the integrity of even a Super 8 frame.

    4K is the most you would need for 16mm, which you would scale down to 2K. Even if you footage resolved only SD, you still want a good HD scan, as upsampling SD to HD is not as pleasant as an oversampled frame. Colour depth is important as well.

    Roughly: for Super 35, 6K scan, 4K downsample; for VistaVision, 10K scan, 8K downsample.
     
  9. From: http://www.kodak.com/KodakGCG/uploadedfiles/motion/h-1-7267.pdf

    Kodachrome 25 movie film goes up to 80 line/mm, or 160 pixels/mm.
    That is at the 10% point, which is pretty low. Some curves end at a higher point.

    160 pixels/mm would give 1280 across 8mm, or 2560 across 16mm.

    Is there use in scanning at higher resolutions?

    When digitizing images, one needs an anti-aliasing filter, to remove higher
    spatial frequencies before sampling. DSLRs use a birefringent material.
    Cheaper digital cameras depend on the limitations of the optical system
    to limit spatial frequencies.

    As far as I know, scanners don't have an antialias filter, but also depend on limitations
    in the optical system. A spot scanner, for example, will have a spot large enough not to
    resolve too high resolution.

    Ideally, an antialiasing filter should have a sharp cut just below half the sampling frequency.
    As real filters aren't quite that good, it might make sense to sample at a higher frequency,
    digitally low-pass filter, and then resample at a lower frequency. This isn't hard to do
    at audio frequencies, but as well as I know, it is usual to simplify the process for
    video. The processors in HDTV sets aren't fast enough to filter with a nice high-order
    filter and resample at the needed resolutions and frame rates.

    Now, what is at higher spatial frequencies in film? For silver-based films there is the
    grain structure itself, which is pretty high frequency (sharp edges). For color films,
    dye clouds have much less structure, but there is still some, and it is completely
    useless for the actual image.

    If the antialias filter isn't good enough, then the high frequencies from grains alias into
    lower frequencies in the digital image. Maybe less for dye clouds. Once it is aliased,
    no filtering can get it out.

    But okay, sample at a higher frequency, and then downsample using a higher order
    digital filter, with a nice sharp cutoff. I suspect that will take somewhat longer than
    the length of the movie, but not so much longer that it can't be done.

    Note that individual movie frames have fairly visible grain. When watching a movie,
    the human visual system averages over successive frames, greatly reducing the
    visible grain, (relative to a still frame). I am not so sure how that works once
    it is digitized.
     
  10. Some of the perceived "quality" of movie film comes from human persistence of vision blurring and merging the random position of dye clouds/grain from frame to frame. I believe that if the grain is filtered out, then this effect will no longer take place and perceived quality will be reduced. With the additional effect that the filmic look will be lost.

    WRT film resolution on a single frame basis.

    "Did "they" provide any independently verifiable data to support their claims?"

    There is no anti-film conspiracy of an anomymous "they".
    It can easily be shown, and seen, that (usably fast >= 100 ISO) film contains little to no detail above 4000 pixels-per-inch, or around 160 pixels/mm. Since 16mm film is only 10.25 x 7.5mm in frame size, then its detail can be fully resolved with a 1650 x 1200 pixel scan. Equal to only a 2 megapixel digital image.


    Scanning at an HD resolution of 1080 x 1480 gets pretty much all of the detail it holds out of it, but as I said above, the result would probably no longer look like film. Especially if digital enhancement of colour and scratch/dust removal was applied.
     
  11. I think the answer partially depends on what your goals are. There is a limitation on how faithfully a lens can capture what's in front of it. Then there is a limitation on how well film can reproduce what's coming through the lens.

    Then finally, there's a limitation on how well a scan can faithfully reproduce what's on the film. Assuming that this is a negative, also realize that printing a positive in the traditional way won't be a completely faithful reproduction of the negative either.

    What it sounds like the question is once we get over 2k with 16mm, is not how faithfully the scan will reproduce the image captured on the film, but how faithfully it will capture the detail of the film itself. Now, I'm assuming there's a reason you chose film rather than digital. So I'm also assuming that it's important to retain at least some of the detail of the dye clouds or grain. At the same time, you are scanning, so this is a hybrid process. It's not going to be exactly like viewing a film for your audience.

    What I would be asking myself is, who is the audience? How are they going to be viewing this? What is it that's important to me for them to see? And of course, what is my budget and is my project best served by spending the money on the higher res scan or somewhere else? It is true what someone said, you can always downsample but you can't upsample and get the same results. It is also true that they aren't going to refund the difference in scanning costs if you end up downsampling. And there's nothing to stop you from scanning it again in 5 years when 5k scans cost half as much as they do now.

    I think we are always tempted to try and get the most we possibly can out of a frame when it comes to scanning. But we've made many choices prior to that that effectively limits how high the image quality is going to be. Did you spends hundreds or even thousands on cameras and lenses? Was it taken by a professional photographer? How much did you spend on processing (developing) and who did it?

    Scanning is the one part of the process you can choose to spend more money on later. Once the film is shot, it's too late to get a nicer lens.
     
    Last edited: Jul 3, 2017
  12. "Since you state it is so easy, you have a chance to show what you have done to support your assertions."

    Les, I used to scan my film on dedicated film-scanners, and lately have been copying negatives with high resolution DSLRs. I can categorically say that you'll see no more image detail by increasing the scan "resolution" above 4000ppi. This can be shown (which I've done to my own satisfaction) by copying a negative at 4x magnification and comparing it to a 1:1 copy using the same 36 megapixel camera. There is no difference in the amount of detail to be seen. All you get is a more detailed image of the grain structure. The 4x DSLR image is equal to scanning at 16,000 ppi; a figure that can't be acheived by any dedicated scanner.

    But let's turn this around. What evidence do you have to the contrary Les? I'd love to see some 5 or 6 thousand ppi film scans that show more detail than my 5000 ppi equivalent D800.
     
    Last edited: Jul 4, 2017
  13. Imagine that - actual evidence! Mind you the D800 is handicapped - its files are nowhere near a true 36Mpx. But OTOH Tech Pan nonetheless does resolve an amazing amount of detail.
     
  14. I doubt his movie would be shot on tech pan though.

    There's some interesting numbers in this article from Cool Conservation. Not sure what the resolution of Vision 3 50D or 500T is in terms of lp/mm. The article used a figure of 80 lp/mm and that was a bit over 4000 ppi. And as I said before, there's other factors that will impact the actual resolution achieved vs what is technically possible for a certain type of film. And there's a lot of stuff moving around in a movie camera. Registration isn't perfect.

    I'm not 100% convinced either way. If money's not a problem then go for the 4K, but since the OP bothered to ask, I think they want to know if it would be money wasted or not. I suspect it probably would be, - again depending on what their goals are.
     
  15. Well, I can show even greater resolution from Lippmann plates, but you can't put those in a cine camera.
    You'll note I made the proviso "
    (usably fast >= 100 ISO) film"
    IMO Technical pan isn't usably fast, and is so picky to develop that it's barely useable for continuous tone work at all.

    Show me something 3 dimensional shot on T-max 100 or a colour negative film that's been commercially processed. Not some geek trying to prove that slow copying film has a high resolution - well durrr! Ask someone that used FP4 or Ektachrome or Portra day in, day out for 40 years how good film is for normal use.

    This film vs digital argument is now over 10 years past its sell by date. Let it go!

    "Kodachrome 25 movie film goes up to 80 line/mm, or 160 pixels/mm."
    - Correction. It went up to 160ppmm
     
    Last edited: Jul 6, 2017
  16. Like I said, my experience in STILL film is that I can grain resolve Tri-X shot at EI 400 and developed in straight D76 at 3200 DPI.

    roll 1 photo 8 rafael crop.jpg

    (scan from in-date 120 Tri-X shot in a Bronica SQ-A with an 80mm Zenzanon, and scanned on my not-so-great Canon 2400f)

    View attachment roll 1 photo 8 rafael.jpg
     
  17. I have a bunch of 8mm home movies in Kodachrome from 40 years ago, maybe longer. I want to send them out for scanning. They offer HD and regular. What is the practical scanning resolution I should buy?
     
  18. I also participate in an 8mm forum. Even with 8mm there are those that would argue that there is a genuine difference between 2k and lessor scans. Most agree though that HD is sufficient for 8mm and Super 8. You were asking about SD vs HD though. A well done 8mm movie can be of HD quality.

    Many years ago my brother recorded all my father's home movies on VHS. It ended up being about 3, 90 minute tapes worth. He made one copy of each. Those he sent to my other two brothers and myself (he lives on Island in the Pacific). So he has the originals and the other brothers each have a copy of one of the 3 "masters". VHS is much lower quality than SD but I'm happy to have my 1/3 copy of the collection. I've digitized some of it and posted it on youtube to share with my relatives and so have my brothers.

    I would much rather have even an SD copy but the VHS is better than nothing. I've talked to my brother about re-scanning them all and we've agreed to wait until prices drop for HD, but if we didn't already have the VHS copies, I'd opt for scanning them at SD just so we'd have something that we could all see.

    So I'd frame it this way: HD if it's not a financial burden but if that means you'd end up putting it off, then I'd go ahead and get the SD transfers. SD video that you can watch at your convenience is much better than a box of film that no one ever sees. I'd imagine the reason for the movies being made was to capture the moments, and they weren't necessarily worried about achieving the highest image quality anyway.
     

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