Best practices: scanning 8mm film, resolution and codec choice

[CaptainTivo]

Hi folks, I need to tap your expertise for a project I have. I hope this is the right sub-forum, I do not see one dedicated to film scanning.

I have some 8mm films (both standard and Super 8) from the 1950's and 1960's that I want to have scanned. After some research, I found this recommendation for a scanning service: here (http://www.digitalfaq.com/forum/video-workflows/2960-suggested-film-dvd.html).
Cinepost (https://www.posthouse.com/) is the company I picked. They do professional quality scanning using a wet-gate and since much of my footage has scratches, I think that would help.

My planned workflow:
1) lossless cut editing (no re-compression)
2) stabilize, de-grain, sharpen, color correction and final output using Avisynth

My main question today is, what codec should I ask for from the scanning people. They offer:

(1920 x 1080) - ProRes 422 HQ $25 per 5" reel
(2048 x 1450 ) - ProRes 422 HQ $35 per 5" reel

They normally do a full frame with black pillar boxes to fill the frame. I asked for no pillar box since that would mess up the avisynth filters and they said they could do that.

My immediate questions:
1) should I go with HD or 2k? I have heard that 2k is overkill for 8mm
2) should I go 10 bit or 8 bit pixel depth?
3) is ProRes 422 HQ (high quality but lossy) good enough?

I downloaded a sample and played around with the avisynth filters and it looked really good (but the original film was high quality). Below is the MediaInfo on the clip. The only thing that looks wrong to me is the Display Aspect Ratio of 1.412 since the original Super 8 was 4/3 (1.33). When running this in VLC, the picture is horizontally squeezed. I guess that can be fixed using an avisynth filter, right?

Thanks for any help.


General
Complete name : C:\Users\Hunter\Desktop\2K Thompson S8mm Reel 01.mov
Format : MPEG-4
Format profile : QuickTime
Codec ID : qt 0000.00 (qt )
File size : 4.45 GiB
Duration : 3 min 25 s
Overall bit rate mode : Variable
Overall bit rate : 186 Mb/s
Encoded date : UTC 2020-02-13 12:16:15
Tagged date : UTC 2020-02-13 12:18:09
Writing library : Apple QuickTime

Video
ID : 1
Format : ProRes
Format version : Version 0
Format profile : 422 HQ
Codec ID : apch
Duration : 3 min 25 s
Bit rate mode : Variable
Bit rate : 186 Mb/s
Width : 2 048 pixels
Height : 1 450 pixels
Display aspect ratio : 1.412
Frame rate mode : Constant
Frame rate : 18.000 FPS
Color space : YUV
Chroma subsampling : 4:2:2
Scan type : Progressive
Bits/(Pixel*Frame) : 3.486
Stream size : 4.45 GiB (100%)
Title : Core Media Video
Writing library : abm0
Encoded date : UTC 2020-02-13 12:16:15
Tagged date : UTC 2020-02-13 12:18:09
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709

[Emulgator]

Here a quick glance what to expect from 8mm film stock:

Gauge Gate W/H Gate W/H PAR
Reg8 192x145 mil 4,88x3,68 mm 1,324137931
Super8 245x166 mil 6,22x4,22 mm 1,475903614

Normally you would take care of any cropping,
but you asked for removal of black pillars, and so a stretched picture is to be expected.

apch 4:2:2 @ FHD can be enough for Regular/Super 8.
Scanner might be a FHD cam.
For blu-ray distribution you would ask for 1920x1080 with black pillars,
and crop/resize anyway down to 1440x1080, pad to 1920x1080.
A final FHD 4:2:0 encode may match theoretical B/W 4x4µm film grain sizes (8x8µm for Chroma).
B/W film stock delivers that by nature, 5µm low-sens to 10µm hi-sens.
Going color: only low-sensitive positive stock will deliver that fine detail,
negative stock delivers and needs less resolution, and less stops.

Their better scanner will deliver 2048x1450, so the according sampling PAR is fixed to 1.412 anyway.
Useful for a 4:3 or so source format.
This is not a FHD cam, so expected to have more useful stops.
If you can afford that: Better.
And if you can afford 10bit, this can be valuable while stretching dark/underexposed material without banding.
Again: You decide how to frame your film, crop/resize, pad to maybe 1920x1080, if aiming for blu-ray.

I would ask for samples of both scanners, then decide.
Differences are often quite noticeable.

[johnmeyer]

I do film transfers myself, and have done so for almost twenty years. Here is what I have learned.

For 8mm film, you can actually use SD resolution (656x480 or 720x480 non-square pixel). I've done actual tests, and you do not get any more resolution with an HD scan. Therefore, you most definitely do NOT need to pay for the higher res scan. 1920x1080 will be absolutely fine, and is probably a overkill.

You ask about post production work, and if you have read through the three extremely long threads in this forum started by "VideoFred" you will see that he actually sometimes down-res's his captures to a lower resolution in order to make the workflow faster. I do much the same thing, capturing with an HD camcorder but having it down-res to SD. This provides a little better quality than capturing using an SD sensor.

If you are dealing with 1920x1080, almost half that horizontal resolution is lost because 8mm film is almost perfectly square (Super 8 is 4:3). Thus, you will have big black pillars on either side. Since I do a lot of 8mm transfers, I added a temporary crop facility to my version of VideoFred's script. You specify the width of the pillars on either side, and my script removes them for the duration of the script's processing, but then adds them back at the end, so you can save at your original resolution.

However, if you have them crop it for you, then you won't have the problem, unless they still leave a sliver of black at the borders. If you stabilize the film, you MUST eliminate ALL black borders, no matter how small, because the stabilization will cause that black to wander into the frame, and it will look horrible.

Mediainfo has no way of knowing the aspect ratio of what is in the file, other than through whatever header was put on it, so that part of its information is probably not useful.

10-bit depth may not be needed, but I agree that it will help avoid contouring on big, uniform flat areas like walls and clear sky.

Whatever they send to you should have the correct aspect ratio when played. If it is squeezed, you need to ask them about that.

Super 8 is ALWAYS played at 18 fps. Regular 8mm did not have a standard, but most of it was filmed at 16 fps, so I'd start with that. You can easily re-time the playback speed, without any loss of quality. If you are lucky enough to find a few frames with a clock that has a sweep hand showing in the frame, then you can calibrate it from that.