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Removing sprocket holes/curvature from film scan best practices


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#1 Larry Miles

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Posted 02 June 2018 - 02:05 PM

This may be a very noob, obvious question:

 

I shot a roll of Super 16mm film (to be clear: Super 16mm camera, lenses, 16mm Kodak film). My

understanding is that the native aspect ratio for Super 16mm is 1.66, and I was told that my film, scanned on a Scanity, was scanned at 1.66

 

The resulting individual frames from the scan include portions of the sprocket holes as well as the curvature at the corners. These are elements that need to be removed from the final image. The only ways I can see to do this are to either crop them out or to enlarge the image until they are no longer seen.

 

It seems to me that to crop (blanking) them out would be to change the aspect ratio, even if only minimally, and to enlarge the image is to degrade the image by reducing its resolution, if only minimally. To need to enlarge the image means that the resolution at which I had it scanned isn't "true," meaning it's not truly 4K or 2K if I have to enlarge the image to remove these elements.

 

Am I correct? Are these problems taken care of when an aspect ratio card is properly filmed at the head of the reel? Is there a standard protocol that is followed with scanned images that include pieces of the sprocket holes and curved corners (as in, enlarge it .023 percent, etc.)? Is it the fault of the lab? Is it the fault of my camera?

 

In case it's relevant, I am using Davinci Resolve 12.5 (free version). Davinci shows the whole scanned frame (with the elements I wish to remove) as being 1.66.

 

Thank you.


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#2 Stephen Perera

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Posted 04 June 2018 - 02:57 AM

You have to specify you want a 'full gate' scan......make it clear you do not want the sprocket holes etc......BEFORE the lab does it......simple communication thing

 

I had stuff done at Cinelab London recently of my REGULAR 16mm film scanned to the width of the frame format thus 2048 x 1556 


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#3 Perry Paolantonio

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Posted 05 June 2018 - 07:03 AM

Overscanning is popular right now, and is what most people ask us for. In order to avoid upscaling to crop out the perfs and frame edges later, you need to scan at a slightly higher resolution. For example, if you ultimately want a 2k film frame, but you also want it overscanned, you want to do higher resolution scan at something like 2.3k. Or you need to ask for the film to be cropped if you don't want overscan at all, and specify the desired file resolution.

 

Unfortunately, there's not a ton of standardization in the language used here. Different labs refer to things differently. (and if you're really old school, even the term "overscan" has the opposite meaning, from back in the video days). If this is critical, it's helpful to provide a screen shot of what you're looking for, because most modern scanners can be pretty flexible about this sort of thing. 


Edited by Perry Paolantonio, 05 June 2018 - 07:04 AM.

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#4 Larry Miles

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Posted 05 June 2018 - 08:04 AM

Thank you for your responses.

Does shooting an aspect ratio card at the head of the reel solve, or help solve, this issue?
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#5 Perry Paolantonio

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Posted 05 June 2018 - 10:54 AM

If you do and you tell the lab to crop to that card, sure. I can't remember the last time we saw that though - they show up occasionally on higher end shoots, but if someone asks for it cropped, we just do it as big as we can without showing the frame lines.  


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#6 Robert Houllahan

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Posted 05 June 2018 - 02:26 PM

I typically scan S16mm (not overscan) to 2K 2048x1306 or 4K 4096x2612 where the film camera gate is the full width (2048 or 4096) and the up/down is slightly overscanned so if there is any vertical camera gate instability it can be dealt in post with without losing resolution.

 

I think most of the scanners have (Xena does) a guide tool where you can setup the guide to be the desired pixel dimension you want (1.66 for example) and set that to the film camera gate in setup to verify the pixel aspect ratio before scanning.


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