Negative (film) conversion to positive in dt or GIMP (b/w only)

Software darktable
1

Hi y’alls,

is there a proven procedure or even reliable function to convert b/w negatives to positives in darktable or GIMP?

I will shoot the negatives with my DSLR through a macro lens, using a flash behind it. All OK, no problem. Has one or maybe both of the aforementioned programs a “conversion” function that I never knew of?

Thanks in advance

2

Hi Stefan,

I do not need this procedure particularly often, but
when I do, dt’s modules invert followed by a tone curve
seem to work well.

Have fun!
Claes in Lund, Sweden

3

Thanks, good to know there is an “invert” module. I guess it’s just what I am looking for ;o)

4

Gimp also has an invert function.

5

Thanks - so I have two options. That’s WAY better than what I thought. I will go through my negatives over the holidays, get me one of those macro-adapters and photograph my negs, then convert them.

My personal Christmas present to me was the overhaul of my trusty rusty Nikon F2 by Sover Wong in the UK. It cost me the price of two used Nikon F2 in “as new” condition, but at least I know than mine is really “as new” with new foams, cleaned prism, measured times and new grease. There is a lot of film coming in the near future …

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6

Why so negative???
The Gimp has at least three built-in commands for this.
Then you have G’mic, and ImageMagick, and…

Positively Yours,
Claes in Lund, Sweden

7

Hm, for b/w this may be less important, but for colour it is extremely helpful that darktables invert module does the inversion based on a picked neutral colour to remove the orange mask of colour film negatives. However, there seems to be some difference dependent on where the pixel data originates from. I never made it work with raw images of photographed negatives, but it worked well for “real” scans.

8

What is the difference between “photographed negs” and “real scans”?

Have fun!
Claes in Lund, Sweden

9

I assumed by “b/w only” he meant traditional b/w film, tri-x, delta series, etc, developed in b/w developer such as D76. That film doesn’t have the color mask, which makes inversion a lot easier.

If he’s shooting something like Fuji acros, then it might not work as well.

10

Correct. I am with Kodak Tri-X since the late 70s and use - any port in a storm - Ilford HP5+ if no Tri-X is available.

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11

The origin of the pixel data. One is bayer raw demosaiced, the other is real 3 colour channels per pixel tiff. Why it makes a Difference I did not yet find out. Maybe it’s to do with pixel pipe position which may improve with 3.0.

That’s what I assumed as well. But as there may be people reading this that do colour film photography as well, I wanted to make them not miss this useful feature.

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