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07-08-2019, 03:41 PM   #1
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Digitalizing negatives with Darktable

I completly underestimated the effort.

I wasn't completly satisfied with the results of the scans my local lab provided (and high res .tiff scans are expensive), so I decided to scan the negatives with my K-3 myself - the youtube tutorials suggested that it's a fairly simple process. What I didn't realize was that most of them are using a lightroom plugin (NegativeLab Pro), which costs 100$. Since I'm using darktable anyways I thought I don't need that, I can just put some effort in creating some presets once for different films and use those afterwards.

The first probelm I encountered was that the invert module in darktable doesn't really cut it. Even with black and white film I get strange results, so I figured it's easier to just invert the base curve. After that I adjust the levels to get the picture to look less flat. While this works quite nice for b/w, colorfilm somehow doesn't work this way. Inverting the base curve works, but adjusting the levels the same way as with b/w leaves me with a desaturated picture. White balance is another story, getting the color of the film right (one of the reasons why I shoot film in the first place) is super hard. I attached two I my first attempts shot with Fuji Supercolor 200.

Has anyone of you found a way to create presets that actually get the color right? I'd be happy to hear your workflow and your ways of tinkering!

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07-08-2019, 04:01 PM   #2
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With the invert module, did you pick a portion of the unexposed negative for color correction? It works well I'm my experience. The blue cast in the second image makes me think it was correcting off a different color. It has a default orange tone but that rarely is accurate right away.
07-08-2019, 04:08 PM   #3
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QuoteOriginally posted by aaacb Quote
With the invert module, did you pick a portion of the unexposed negative for color correction? It works well I'm my experience. The blue cast in the second image makes me think it was correcting off a different color. It has a default orange tone but that rarely is accurate right away.
On the picture with the house I used the tone curve. If I use the invert module (after setting white balance), I get the result below.
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07-08-2019, 04:42 PM - 1 Like   #4
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QuoteOriginally posted by Luppenko Quote
On the picture with the house I used the tone curve. If I use the invert module (after setting white balance), I get the result below.
That's surprising... well, great job correcting it manually then, especially on the first image, I never could do better than that
I see in the image info that it says white balance is manual, is that on the k3? I'm just wondering if the white balance from darktable is somehow interfering with what invert is supposed to do. What kind of light do you use for scanning? I have a lightpad normally marketed for drawing (5600K) and keep the camera in auto white balance. If you don't mind sharing a raw file, I can give it a shot though of course I may do even worse, and it may take until the weekend; but if it's successful, I think sending back the .xmp would allow me to share what I've been using.

07-08-2019, 10:24 PM - 1 Like   #5
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DId you try this script: Why is it so hard? - C41Lab - The easy way to create positives from color negatives It is free
And there is KodakRock plugin (but it costs money: $100) I tried its free version (with watermarks) and it provides the best conversion I achieved myself. Probably I will buy it eventually.
Edited:
Actually, I have to withdraw my comment regarding the KodakRock. It is discontinued on June 30, 2019, and is not available for download or registration anymore. Sad. It was good software.

Last edited by jumbleview; 07-09-2019 at 08:30 AM. Reason: Added info about KodakRock discontinued.
07-09-2019, 12:00 AM - 3 Likes   #6
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Use reversal film
07-09-2019, 10:18 AM - 1 Like   #7
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QuoteOriginally posted by aaacb Quote
That's surprising... well, great job correcting it manually then, especially on the first image, I never could do better than that
I see in the image info that it says white balance is manual, is that on the k3? I'm just wondering if the white balance from darktable is somehow interfering with what invert is supposed to do. What kind of light do you use for scanning? I have a lightpad normally marketed for drawing (5600K) and keep the camera in auto white balance. If you don't mind sharing a raw file, I can give it a shot though of course I may do even worse, and it may take until the weekend; but if it's successful, I think sending back the .xmp would allow me to share what I've been using.

Thank you! I uploaded the raws (and .xmps) here: Dropbox - negative raw - Simplify your life
It would be really cool to see how you approach it.

I'm also using a lighttable for drawing and set the white balance of the camera to 5000K, but I'm adjusting it in darktable. After that the colors of the negative look accurate, it's just after converting that it looks off.

---------- Post added 07-09-19 at 05:22 PM ----------

QuoteOriginally posted by jumbleview Quote
DId you try this script: Why is it so hard? - C41Lab - The easy way to create positives from color negatives It is free
And there is KodakRock plugin (but it costs money: $100) I tried its free version (with watermarks) and it provides the best conversion I achieved myself. Probably I will buy it eventually.
Edited:
Actually, I have to withdraw my comment regarding the KodakRock. It is discontinued on June 30, 2019, and is not available for download or registration anymore. Sad. It was good software.
I'm going to check out C41Lab, but at a first look it seems a bit tedious too (and I'm not used to work with windows command).

Using reversal film might really be a good idea
07-09-2019, 10:33 AM   #8
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related discussion

RawTherapee vs Darktable: invert scanned B&W negatives - RawTherapee - discuss.pixls.us

07-09-2019, 04:34 PM   #9
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QuoteOriginally posted by Luppenko Quote
I'm going to check out C41Lab, but at a first look it seems a bit tedious too (and I'm not used to work with windows command).
D
If prefer Unix/Lnux you may try this one
Fred's ImageMagick Scripts: NEG2POS

( I did not try it yet but I will sometime)

There are a lot of scripts: two of them "neg2pos" and "negative2positive" do conversion of scanned images.

Last edited by jumbleview; 07-09-2019 at 04:41 PM.
07-10-2019, 06:39 AM   #10
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QuoteOriginally posted by jumbleview Quote
If prefer Unix/Lnux you may try this one
Fred's ImageMagick Scripts: NEG2POS

( I did not try it yet but I will sometime)

There are a lot of scripts: two of them "neg2pos" and "negative2positive" do conversion of scanned images.
I tried to get the scripts to work, but while the people who wrote the scripts know what they're doing, well, I don't know what I'm doing. For the neg2pos I'd need to simulate unix/lnux environment with cygwin since I use windows and that's where I ran out skills.

The C41Lab script doesn't work somehow either, I assume because it was written 2013 and is not compatible with windows 10. More likely: I'm doing something wrong.
07-18-2019, 04:53 AM   #11
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QuoteOriginally posted by Luppenko Quote
It would be really cool to see how you approach it.
Took me a while to remember about this, but here it is, you should be able to download them. I put a version with the default color balance, one where I cooled it down a bit (ending in _01), and the xmp file from darktable. All I did was, first thing before cropping or anything else, pick a small area on the unexposed negative with the invert tool. Hope this helps.

Dropbox - Invert film - Simplify your life

Last edited by aaacb; 07-18-2019 at 06:51 AM.
07-18-2019, 09:06 AM   #12
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Not sure how much help as I do not use darktable, but correction should be reasonably easy (at least manually per image!). Effectively you are correcting per channel for both colour and contrast

Invert RGB curve first is a good start but then you will also need to correct individual channels or/and WB. The problem for producing a preset is really getting colour balance correct. You may be able to set up to sync images taken in the same light?

A quick play using LR (Darktable should be very similar?). Invert RGB composite (get blue/cyan image first) then adjust individual R, G and B channels to taste.


It is worth noting that you should really be cropping to the image area in camera rather than showing the surrounding as you have done here as this will make correction easier
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07-18-2019, 11:29 AM   #13
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QuoteOriginally posted by TonyW Quote
It is worth noting that you should really be cropping to the image area in camera rather than showing the surrounding as you have done here as this will make correction easier
Getting a tighter crop also increases the resolution. However, for tools that have automatic color correction using the orange film base, such as my example in darktavle above, you still need a small portion of the negative outside of the frame to calibrate it. There are presets, but choosing by hand is best to correct for variables such as the light source.
07-29-2019, 12:32 PM   #14
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Thanks for your effort guys! I've been fiddling around in the meantime and came to some good results. What seems to work pretty well is to

1. set whitebalance
2. invert the tone curve
3. automatically (or picking a neutral grey/white part in the picture) adjust the midtones gamma/power with the color balance tool

I've been also trying to adjust channels of the tone curve individually, but darktable offers L/a/b channels. I don't need the color balance tool after that. That works too, the results are similiar to the process above. Is there a way in darktable to get to the r/g/b channels?

Fot the atcual "scanning" I intentionally left some of space around the picture to have the name of the film and the sprocket hole in the final pcitre. I think that looks cools (and makes the dual process visible)
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08-06-2019, 02:12 AM   #15
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I find it too much blue...
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