Converting colour negs

Because both the cat and the bus stop were from the same roll of film with the same camera I suspected the Gamma adjustment stage was the problem. These attachments are from more tests using an earlier method with my venerable G5 Mac and PS Creative Suite (CS), the original version. I would be interested to see how it comes out under scrutiny.

gbroadbridge said:

The picture is very blue. Something is wrong with your colour management.

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When I look at it closely with the colour picker it does have a tendency to blue/cyan. This is the complimentary to the orange mask so I suspect the gamma correction stage is where the problem lies. I have posted another version done on PS which looks better.

Still puzzled by the apparently strong cast you are seeing because it is very slight here and I have never had major problems with colour trusting in Apple's equipmant. What sytem do you use. I ask because I have articles published online and I would not like to think some of my illustrations are so skewed colur wise.

Tony39 said:

Still puzzled by the apparently strong cast you are seeing because it is very slight here and I have never had major problems with colour trusting in Apple's equipmant. What sytem do you use. I ask because I have articles published online and I would not like to think some of my illustrations are so skewed colur wise.

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I'm using a fairly generic HP LCD here, but it's calibrated. I don't doubt your Mac shows colors just fine - at least well enough to see the kinds of casts we're dealing with here.

What constitutes a strong or a slight cast is of course also subjective, and it's well-known that sensitivity to color varies greatly between people. Then there's the aspect of practice and experience. The more time people spend with this, the more sensitive they tend to become to color casts. What may look like a minor issue to one person can be a massive problem to another. I readily acknowledge I'm on the latter part of the spectrum; I respond quite strongly to color to begin with and spending a lot of time optimizing it in prints & scans makes me all the more focused on it (which isn't to say I always get it right!)

Your adjusted version is better, although it still doesn't look completely natural. Color balancing is a bit of an art and perhaps part magic; in all brutal honesty, operations like "auto levels" etc. really don't cut it in practice. It may give an acceptable quick preview of what's on the image, but it won't be optimal. Trying to fix things once these kinds of auto-adjustments have been done is often a lot more work (and sometimes even impossible) than just starting over with the raw capture of the negative and then adjusting the curves manually as I suggested in my post #14.

Tony39 said:

Because both the cat and the bus stop were from the same roll of film with the same camera I suspected the Gamma adjustment stage was the problem. These attachments are from more tests using an earlier method with my venerable G5 Mac and PS Creative Suite (CS), the original version. I would be interested to see how it comes out under scrutiny.View attachment 414621


When I look at it closely with the colour picker it does have a tendency to blue/cyan. This is the complimentary to the orange mask so I suspect the gamma correction stage is where the problem lies. I have posted another version done on PS which looks better.

Still puzzled by the apparently strong cast you are seeing because it is very slight here and I have never had major problems with colour trusting in Apple's equipmant. What sytem do you use. I ask because I have articles published online and I would not like to think some of my illustrations are so skewed colur wise.

Click to expand...

In my (limited) experience with converting color negative film to positive, the fact that "both the cat and the bus stop were from the same roll of film with the same camera" is of little significance. It seems to me like whatever adjustments were required for one frame may not necessarily give the same results with the next frame, expecially when the lighting and exposure are different from frame to frame.

On my calibrated iMac monitor, this version of the bus stop photo looks much better. The blue tint in the deep shadows is now mostly gone, but I think there may be still be some lingering blue cast in the midtones...? I would expect the paving "stones" (more likely concrete?) to be less blue and more gray?

This photo brings up two different issues:
- First, what steps are necessary to get the colors "right" when inverting color negatives. (And by "right" I mean getting the colors to look the way you want them to look.)
- And second, what steps are necessary to maintain a color managed workflow that works for your intended purpose (printing, internet, etc.). I probably listed those issues in the wrong order, because you can't really solve the first problem unless you have a reasonable color managed workflow.

The fact that you can't see the blue color cast that the rest of us are seeing suggests a color management problem. If so, I would concentrate on that before spending a lot of time inverting and color correcting negatives.

One part of color management is calibrating your monitor. Apple computers have always come with a software tool called the "Display Calibrator Assistant" to help adjust the colors on your monitor. In the past (back in the days of CRT displays), I was able to get pretty good results with Apple's software calibration. But when I switched to LED displays, the Apple calibration software got harder to use and I trusted the result less. My suggestion would be to buy a display calibration package which includes a hardware sensor and software to do the job properly.

runswithsizzers said:

The fact that you can't see the blue color cast that the rest of us are seeing suggests a color management problem.

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A friend of mine spent a fair bit of time and a significant amount of money a few years ago trying to learn how to print with Cibachrome/Ilfochrome materials. He ended up getting very frustrated.
His friends couldn't figure out why he was having as much trouble as he was until his wife mentioned he was "colour blind"!
So there could be other sources for the difficulty

Photoshop

MattKing said:

A friend of mine spent a fair bit of time and a significant amount of money a few years ago trying to learn how to print with Cibachrome/Ilfochrome materials. He ended up getting very frustrated.
His friends couldn't figure out why he was having as much trouble as he was until his wife mentioned he was "colour blind"!
So there could be other sources for the difficulty

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I said “suggests” not “proves” — add color blindness to the list of things to be ruled out.

I scan raw in vuescan and use darktable with it's negadoctor plugin. Adjusting first for film mask and contrast, a few auto white balances, and then fine tweaking. Some films are easy and fast, some others, especially expired or strange light, need a bit more adjustment. But I'm general in works for me.

koraks said:

I'm using a fairly generic HP LCD here, but it's calibrated. I don't doubt your Mac shows colors just fine - at least well enough to see the kinds of casts we're dealing with here.

What constitutes a strong or a slight cast is of course also subjective, and it's well-known that sensitivity to color varies greatly between people. Then there's the aspect of practice and experience. The more time people spend with this, the more sensitive they tend to become to color casts. What may look like a minor issue to one person can be a massive problem to another. I readily acknowledge I'm on the latter part of the spectrum; I respond quite strongly to color to begin with and spending a lot of time optimizing it in prints & scans makes me all the more focused on it (which isn't to say I always get it right!)

Your adjusted version is better, although it still doesn't look completely natural. Color balancing is a bit of an art and perhaps part magic; in all brutal honesty, operations like "auto levels" etc. really don't cut it in practice. It may give an acceptable quick preview of what's on the image, but it won't be optimal. Trying to fix things once these kinds of auto-adjustments have been done is often a lot more work (and sometimes even impossible) than just starting over with the raw capture of the negative and then adjusting the curves manually as I suggested in my post #14.

Click to expand...

Thanks for that. I did use the quickie run from all 36 frames here so the message is to be more precise after first review versions.