Restoration of color negatives
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April 28, 2010, 04:01 AM
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Hello littletank (if you are still subscribed to this forum)!
I recently digitized my first color negative. Negatives are not as easy as color slides because of the orange tint. But I know you have already dealt with this problem because I read the conversation you started in a meetthegimp.org forum.
Doing the color correction in Gimp destroys the histogram, so I developed a workflow based entirely in ufraw. If you are interested, we could discuss it here and also post a few examples.
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April 29, 2010, 11:32 AM
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Hi Perkin-warbeck and yes, I am still very interested in anything that can add to my knowledge about the digitising of colour negatives. Would you be kind enough to describe how you copied the negatives and your workflow in ufraw, anything which does not destroy colours must be a good thing.
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April 29, 2010, 02:34 PM
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Hello! I'm glad to see you back again. Here are the steps I used.
* In ufraw, go to the White Balance tab
* Click in the orange border of the negative
* Press the "Apply white balance" button (has an eyedropper icon)
* Go to the Base Curve tab
* Manually adjust the Base Curve until the Live Histogram looks like a "good histogram:" all three curves are roughly centered on the x-axis, the area under curves is maximum. I do this by grabbing the curve at its maximum point (1,1) and sliding it to the left.
* Pipe the image to Gimp
* Colors -> Invert (this is non-destructive). I suppose you could have done this in ufraw by inverting the Base Curve, but I never get good results this way, and I don't know why.
* Duplicate the layer one or more times in Multiply or Overlay mode to enhance the image as required.
Of course the same steps could be done in Gimp. For example, someone in the meetthtgimp.org forum suggested using Easy Zone Adjustment as a shortcut method. I tried this, and found that it works extremely well at both repairing the colors and getting good contrast. However EZA (or Levels or Curves, or anything else you do in Colors in Gimp) wreaks havoc with the histogram. Since I digitize my negatives by photographing them on a light table, rather than having them scanned by a high quality scanner, their resolution is not that good to begin with, and artifacts begin to appear as soon as the histogram becomes the least bit spikey.
What is your method? I have lots more color negatives to do, and I want to have a good workflow before I go further.
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April 29, 2010, 07:50 PM
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To be honest, I have not found a procedure with which I am satisfied. You will have seen in MTG Forum several ideas some of which work well some of the time but not one of which works well all of the time. Now that you have raised the subject I realise that it is time for me to return to the topic.
For starters, I must look again at the copying stage. I use an attachment which fixes to my camera and make virtually a 1 to 1 copy which I believe gives the best results one could hope for. This means, of course, that I do not include the unexposed negative in my image. Perhaps I should forgo this ratio and include a small amount of image outside the actual negative then I will be able to try your idea of using the white balance in a raw converter. I like your idea of using the curves in the raw converter and using Gimp for enhancement and I have a feeling that there may be a raw converter somewhere which has a colour inverter, I'll have a look.
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April 29, 2010, 09:38 PM
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I should have mentioned that before copying the negatives, I do a white balance preset with my camera pointed at the open light table. This should remove any coloration from the light source in subsequent photographs. Then the orange film strip border in the raw file will correspond to true white in the negative and true black in the positive). I adjust the EV until the spot reads 255, 255, 255. I think this works better than playing with the Base Curve.
After inverting in Gimp, the colors look pretty good. For example, they don't seem to have a bluish cast, or at least not much of one (verify using the Histogram tool with Channel = RGB).
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May 01, 2010, 10:37 PM
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I'm also getting some nasty "Newton's rings" from my home-made negative copying setup. I lay the negative on a sheet of opal glass, then lay a clear piece of photographic glass on top of the negative to press it flat. I get the rings because the "sandwich" is not perfect. Some people have posted that their flatbed scanners have the same problem. I assume your copying attachment doesn't have this problem.
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May 02, 2010, 07:46 AM
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I can understand your difficulty and no, I do not have this problem. There is contact between the film and a piece of opal glass, which faces the light source, a low wattage photoflood, there is then only air between the film and the camera to which the opal glass is fixed.
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