This, I believe is a chemical issue. The negatives are rather old, and have been stored in paper envelopes. Some when converted to positives have an uneven brown tinge overlaid on top of the image. On a few of these, they have been in the pattern of the edge of a strip of film showing the perforations.
Known? I don’t know about that, but I do know that if negatives aren’t stored properly they tend to discolour, especially if there are multiple, unprotected negatives stored on top of eachother. Not using the correct materials to protect them (a brown envelope for example) also influences this: Chemicals from the envelope react with the chemicals in/on the film.
There’s also the film itself. Although film is rinsed clean of chemicals when the processing is done, this doesn’t succeed 100%, especially if a 1-hour-service was used to develop them back when. And thus film has the tendency to keep developing, albeit at a very low level. This will be noticeable over a long time period though.
If you are talking about cleaning the physical film itself: I’m not entirely sure, but I don’t think you can. Some of the chemical processes might not be reversible. Dirt and other stuff that has gathered over time on top of the film might be removed, but I would advise you to ask a professional about that. Some of the dirt will have interacted with the top layer of the film.
You can pull these into a editor, one that has a good masking ability, and do a lot of damage control. There probably will not be a one-profile-fits-all solution. So it depends a bit on how much time you want to spend and how important these images are.
EDIT: I had a digital go at this image, just to give you an idea. This took me less then 15 minutes to do, so imagine what you can do if you have a serious go at this:
Hello @DAP,
That looks like chemical damage indeed. I tried to apply a color similarity mask in ART over the brown areas, but even then, it is hard to repair them to an invisible level. Perhaps if you invest a lot of time, you might get less or more acceptable results.
Thank you for your responses. I have about 165 envelopes of film negatives to go through. Each contains usually one roll of film, sometimes parts of several rolls of film, not always the same type. It is taking me about an hour per 20 frame roll to to get a half assed conversion to positives, so at least I can see what is there. I don’t think it is practical for me to spend 15 minutes per frame to fix these. I was really hoping that this was something that could be washed off.
I guess I just have to live with what I can get.
Hello @DAP, I didn’t notice this post/topic. I fully support the advice given above. The resolution of your scanned negative is proper (in the case of editing). Maybe the scanning software has a built-in color-balance? I would use that (due to the large amount of negatives). After that you can always make further adjustments. Scan the negatives as straight as possible, then you don’t lose information with cropping and rotating.
But scan all the negatives now, because the deterioration process will continue. If the above image is an example (nice picture), I would definitely scan them all.
For now, learn to live with the brown tinge. There has been so much change and improvement in Image Processing techniques in the last decade alone. This process will probably speed up as well. Perhaps these kinds of problems can then be tackled in the future, with the new techniques.
Enjoy your wonderful pictures, despite the tinge.
The tool I’m using to “scan” my negatives is a Sony A7R II camera and a color adjustable LED light source.
I am adjusting the color & exposure so that unexposed film records at about 90% full scale for each of the R, G, and B channels (yes, this needs to be different for each type of film I run into). This gets me the best color resolution, but I think it confuses the Rawtherapee tool I am using to convert negatives to positives.
I have had to turn off the white balance as it was getting wildly wrong results.
The reason I have been having to tweak every single photo is that the “copy and paste” of the processing of one photo to another gives wildly varying results. I always capture a bit of the unexposed border of the frame which should be black by definition. I adjust the R, G, and B channels to be the same brightness at the histogram peak for this unexposed part of the picture, and near the bottom of the histogram scale for one picture, copy the processing to the next picture, and find that the entire peak has shifted off the bottom of the scale, or to the middle of the histogram, and the three color peaks have separated significantly.
The exposure and aperture for all of the pictures is the same for all the pictures, and I would expect the color and brightness of the unexposed film to be the same for all frames.
I’ve tried to turn off all automatic adjustments, but obviously I’m missing some. I select “neutral” profile, turn off white balance, then enable the negative processing. I generally adjust the three exponents in the negative processing, exposure compensation, black level, lightness, contrast, saturation, and use the channel mixer. I’m not particularly happy with the results I’m getting, but I’d be much happier if I could copy the processing from one picture to the next without it being wildly altered.
Thank you for your detailed explanation. The nice thing here is that my perception of the scanning process (I imagined a special scanning device for negatives) was different from your scanning reality. Now I see that I can learn something from you, so I can’t give advice. Thank you. This is a lot of work. I wish you the best of luck with this trial and error process and hope you will find a nice workflow.
I think I finally have an explanation for the deterioration of the color negatives. I am near the end of the task of digitizing my collection of negatives, and have discovered that some of the negatives are from 1936. I think some will already know where I am going with this.
All the negatives were stored in a pair of shoe boxes packed tightly together, each roll of film in the envelop it came back from the developer in. The earliest in postal envelopes.
Unfortunately film from 1936 is nitrate film. I have several hundred 3x5 negatives, a few are marked “Safety Film” most are not, and some show evidence of nitrate film decay.
As nitrate film decays, it out-gasses toxic chemicals, one of them being nitric acid.
I now have the task of identifying the nitrate film and disposing of it once it has been digitized as there is a risk of spontaneous combustion as it decays. I should also separate the cellulose acetate film from the polyester film as, although cellulose acetate is not as dangerous, it also decays and out-gasses corrosive chemicals.
