scantools - a few tools to help with film scanning

[Ted Baker]

I have been writing some software to help with film scanning to do the following:

1. Speed up flat bed scanning, so a full platen of negatives can be scanned in 1 pass. So for example I can scan 24 35mm frames in 10 minutes at 2400dpi, on my old Epson 4990.

2. Software to invert both B&W and colour negatives, using the same method that is used in Cineon/DPX. i.e. just about any movie you see that was shot on film in the last twenty years.

It is an open source project so free to use and extend etc. Some of colour code needs some revamping, but I am using it to good effect for my current B&W work.

For a B&W negative the result is roughly what would be printed in grade 00 paper, so I find it a good starting point.
A colour negative results in low contrast image, that should only require a contrast adjustment and some linear colour balancing.

It in its current form it probably only usable if you have some basic programming/development skills, you need a bash shell and Imagemagick. PM me if you need some help, but it is a start.

https://github.com/laurencelumi/scantools

[ericantonio]

This looks awesome. Been busy but I have a v700 hooked up to my ubuntu. I usally unplug and stick it onto my Win10 for some scans like 35mm batch scans which Vuescan can't do. Well, it can but so much easier on windows.

[Pali K]

Thank you for this Ted. Looking forward to trying it out and will let you know how it goes.

[Pali K]

Hi Ted,

Good news is that I got it to work under Ubuntu and have a few notes for you from my testing. I am using Gamma 1 scans from my drum scanners to test and here is what I am noticing. Large images fail to convert and I have noticed anythign over 10MB seem to fail for me all together. It creates at small 386kb file and never finishes. For files that do convert, I am getting very dark conversions even with DMAX set to 1.

Here is the negative I am using in case you want to test it yourself.
Download Original TIFF File



Hope this is helpful!

Pali

[SergeyT]

Hi Pali,

try it with "-dmax auto".

Hi Ted,

I have a copule of notes too (Mac OS X):
1. It is a good idea to have all the variables used in the script initialized at the beginning . Example "exiftool".
2. The script did convert a 128 Mb file for me but would not anything above that. It simply stops using CPU and does nothing.
3. The effect of conversion looks similar to that obtained in Photoshop with either "Subtract" or "Divide" of a layer filled with unexposed border color. The converted image blacks are at r=0, g=0, b=0 (clipped) and white point requiring significant tuning (with Auto Color (Enhance per Channel Contrast; No "Neutralize the mid-tones")). Visually and practically (math and algorithms aside), in my opinion, a simple combination of 2 layers (Invert) + (Curves with Enhance per Channel Contrast; No "Neutralize the mid-tones") provide for more flexibility in balancing the collors as neither Blacks nor Whites appear to be clipped.

Best Regards,
SergeyT

[Pere Casals]

Ted, this is an amazing set of tools...

Thanks for sharing it !

I'll read a bit the code...

[Ted Baker]

Hi Pali,

I am not sure why it does not work. If you send me a PM, with details of

#convert -version
and maybe a log etc.

The colour code at moment does does not have make any adjustments yet for printing density. i.e. Cineon/DPX values should represent how the paper sees the negative instead of the human eye.

I am focusing on using at the moment on about 50 odd rolls of HP5, I can scan a roll in under 20minutes on my flatbed which is big improvement. So I put the colour calibration code aside for a little bit...

Anway,

I did this

#invertscan -c1 -fb 0.914557,0.602957,0.480313 -dmax auto pali.tif
Expirmental code
Normalised values are:
max min
Red: 0.901625 0.311894
Green: 0.591104 0.179248
Blue: 0.447105 0.0554971
using calculated FB: 0.914557 0.602957 0.480313
log() values are:
base shadow DMax
Red: 0.0387892 0.00618483 0.467204
Green: 0.219714 0.00862244 0.526832
Blue: 0.318476 0.0311148 0.937254
TODO need to do check of all three maxes
using auto calculated dmax
dmax: 0.937254
scale: 17952.6
1 image files updated
inverting: pali-P.tif

which results in this:



there is no attempt to balance anything at this stage but the intensity ratios should all be linear or a gamma of 1 except where the film the toe and shoulder compresses these ratios.

I use a curve like this to represent the paper.


and balance the image using linear controls to get some thing like


Eventually I like to incorporate the code directly into Rawtherepee etc.

For BW I have found it very effective.

[Ted Baker]

Hi Pali,
2. The script did convert a 128 Mb file for me but would not anything above that. It simply stops using CPU and does nothing.

Its possible your installation of imagemagick is resource constrained. Try

#identify -list resource

this will list any constraints

3. The effect of conversion looks similar to that obtained in Photoshop with either "Subtract" or "Divide" of a layer filled with unexposed border color. The converted image blacks are at r=0, g=0, b=0 (clipped) and white point requiring significant tuning (with Auto Color (Enhance per Channel Contrast; No "Neutralize the mid-tones")). Visually and practically (math and algorithms aside), in my opinion, a simple combination of 2 layers (Invert) + (Curves with Enhance per Channel Contrast; No "Neutralize the mid-tones") provide for more flexibility in balancing the collors as neither Blacks nor Whites appear to be clipped.

No clipping ever occurs. In the file the darkest information sits at 0, for convenience, and the brightest sits at the maximum, if you use dmax=auto. i.e it will adjust for the density of the negative (-dmax=auto) to use all of the 16bit values available, or you use a set max density value that you choose. For the straight line portion of the characteristic curve the intensity ratios should then be linear in relation to the original scene. i.e a value that is 10 times brighter than another, should just as same 10x ratio as in the original scene. This means the image will appear low contrast on a monitor, print etc.

I am reasonably pleased that it is useful for BW, the single pass scan of entire platten for roll film, speed up the laborious process of scanning a film of a flat bed, and results in a scan that I find easy to work with.

I am still working out a few things with the colour side of things, the main thing that is really outstanding is to calibrate the scanners spectral sensitivity, to match the spectral sensitivity of the print stock which is how the film was designed to work in the first place.

Plus take a few photos from time to time...

[Pali K]

Ted, that are some very impressive results with just simple commands. I'll spend more time with it this weekend and let you know how everything goes. I have decent programming skills as well and will try to study your code and ImageMagick commands to see if I can help out with this project.

Pali

[Pali K]

I think getting the film base values right makes a huge difference. Here is a quick conversion using Ted's commands above followed with simple curve and color adjustments.