Don,

A lot of work or not, there has to be a way to create a corrective mask in Photoshop that you could then apply to a negative scan. I can't believe this isn't done all the time. Am I the only one in the world who scans large negatives?

I think the small minority of people who need to scan large color negatives on a regular basis have scanners that can cover the needed area. However, there are Photoshop techniques that can do what you want. The Photoshop techniques vary from fairly simple to very complicated, depending on the required quality of the conversion and the condition of the color negatives. If your color negatives are fairly old, the dyes may have degraded somewhat, and the degradation can be differential, so that the original "recipe" for the orange mask will no longer hold, and the masked negative colors themselves may have degraded.

Almost all Photoshop techniques for removing the orange mask require that you sample the pure orange mask color (sometimes referred to as "the rebate") in areas of the negative that would otherwise be black in the positive, such as near the sprocket holes in a 35mm negative. This basic orange color varies from one brand of film to another even for new films.

For a fairly simple and effective method, refer to one of Martin Evening's Adobe Photoshop for Photographers books. I happen to have the Photoshop 5.0 edition because that was when I did some extensive work converting color negatives. At one time there were archived message threads covering that here in this forum, although they may no longer be available. This subject probably should be added to the FAQ because it does come up from time to time, and for some reason it is not generally well understood.

In his chapter on "Repairing an Image", Martin Evening presents an ingenious method for Retouching a color negative that can be readily adapted to convert it to a color positive.

If that method is insufficient for your needs, we can go into more detailed methods using Photoshop channel operations (CHOPS). To that end, it will be helpful if you can obtain a copy of the now out-of-print "Photoshop Channel CHOPS" by David Biedny, Bert Monroy, and Nathan Moody (New Riders, 1998). But don't pay a premium price for it -- I have seen exhorbitant offerings priced at several times the original list price. You might find it in a public library. As far as I know, a newer edition of that book was not released. Although it actually refers to Photoshop 4, most of the material is still applicable.

The advantage of the detailed CHOPS approach is that you can deal with variations from one brand of film to another (or from one batch to another) and you can also deal with different amounts of dye degration due to aging and such.

If you don't want to go to that much trouble, simpler methods such as the one presented by Martin Evening can produce acceptable results.

-- Burton --

Powerchute50

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Converting negatives to positives