contrast adjustment turns images yellow. why?

Vipmediastar_JZ

For my understanding just like an FYI.

Scenario: I took some photos and didnt do a custom WB with sb-910 and I do not remember if I put on a color filter on flash. ( I have the macbook calibrated with an x-rite)

When I adjusted the contrast, the photo went from normal skin tones to yellow simpsons style skin tone.
After I did the highlights/shadows/etc. adjustments including contrast I moved the temp slider to a cooler tone to fix the issue for a more pleasing skin tone.

Question: why/how/ does the color temp change drastically expecially with contrast. I used LR for the post.
I tried to google an answer but found none. I'm just curios so that I can learn about it.

Msmoto

Without offering a reason why, I note that If one decreases the highlight brightness, this may shift the color. I know when I pull up shadows or darken an area or change contrast there is often a change in color. Simple brush adjustments seem to correct the situation.

TaoTeJared

Contrast effectively adds density to an image in mid tones down to shadows. I'm willing to bet you had a filter on the flash - I have had skin tones really go out of wack with CTO's and/or with warmer WB settings. Not entirely sure why, but I usually try to be aware of it. I use 1/8 & 1/4 CTO gels only and custom WB without gels in place.

Ironheart

Assuming you are processing a RAW why does WB matter at all? You pick the WB in post, it doesn't matter what WB you had in the camera. Or am I missing something?

Vipmediastar_JZ

True it doesn't matter with raw. However when you adjust shadows and blacks for example the WB/Tint stays the same. I was wondering why it changed for contrast.

on a seperate IT issue, using .jpg im also having a similar issue. All stations have the same color profile, icm linked but they are using a different OS. The images print out with a higher contrast and yellow tint. Everything else is consistent with same printer, same pc same associated color profiles.

i printed both images on both OS and on one it has more contrast and it adds yellow to it. While the photo with more contrast is better on the eyes the yellowing makes the photo unnacceptable.

The issue is with the OS upgrade that we need to do and processing software is not used other than for scanners but they use the same associated color profile.

Ade

It's hard to diagnose without seeing the actual file / image.

In general, increasing contrast may also increase our perception of saturation.

So something to try: starting with the original image, set the white balance, then add some contrast as before. But instead of adjusting the white balance again, reduce saturation instead.

Also, knowing this, if you add saturation and then add contrast, the resulting image (especially skin tones) can easily get over saturated and look very unnatural.

FlowtographyBerlin

In general, increasing contrast may also increase our perception of saturation.

That's the answer to your question. If there's a slight cast in whatever color range, if you push up the contrast or pull the levels tighter, these the casts will just by technical definition increased in saturation and become more visible. Wherever that cast originates, you will have to find out by yourself, might be due to mixed light (wrong gel on the flash), to a slightly-off WB, or all that together.

The saturation effect is also there even if everything is set correctly: Use levels adjustment more deliberately, and you will ruin nice skin tones and get the skin look reddish, orange-y and the like. That's why you always have to go for a little de-saturation if you enhance contrast on the skin anyway.

Msmoto

As an experiment:
Original image:

Contrast increased one "full slider" in LR 5.3

Contrast increased one "full slider" in LR 5.3 plus full contrast brush stroke

Contrast decreased one "full slider" in LR 5.3


Make you own conclusions, but there are some differences. No other adjustments were made.

Ironheart

on a seperate IT issue, using .jpg im also having a similar issue. All stations have the same color profile, icm linked but they are using a different OS. The images print out with a higher contrast and yellow tint. Everything else is consistent
[snip-o-matic].

What OS are we talking about and what specific versions?

FlowtographyBerlin

You're talking about the whole RGB spectrum when you adjust contrast, not just the blacks and whites.

Exactly!

Dealing with this in photoshop is a VERY complicated subject.

Actually: No, it isn't. :-) If you know what the reason is behind this, which you just named, it's easy to treat. Or, let's say: rather easy, you just have to desaturate, either color-selectively or area-selectively (or both). If you wanna get a little more advanced, you can use a combination of that and some... what's that called in English, color shift? The first step, and most important foundation, though, is getting the white balance adjustment to the most neutral-looking tone – which isn't necessarily the most 'correct' setting.

@Msmoto: Excellent illustration, thanks for the work!

I find it funny that this appears as such a "surprise" effect and difficult to handle. It was one of the first issues I ran into when I didn't know anything about retouching and started to use Photoshop to "enhance" images. Increasing contrast increases saturation, it's as logical as that increasing contrast means losing tonal differentiation and 'saturating' the blacks and whites. Translated into the different color channels, as @PitchBlack said, means: saturation.

Vipmediastar_JZ

@flowtographyberlin its not much of a surprise. I just need to know why it happens. I normally would adjust as necessary without thinking of cause and effect.
I needed some info like @msmoto @pitchblack and like you have mentioned so that I can pass that info on.

For comparison I know that if i turn the key on a car it will ignite. But there is more to it such as a starter, fuel combustion etc.. Cause and effect.

Im working with a team that doesn't deal with photography or colors but the comments in this thread will help me explain how the contrast is causing the saturation and we can figure out where the source of the problem is.

My guess it's user error but it doesnt explain how the prints look good until you upgrade os.

The more i tell them about monitor calibration and using the same monitor across the less they listen to me. Thats probably the only hardware that is not consistent acrross. My guess is that somebody decides that the image needs adjustment and they adjust to their liking all while they have been told not to.

Thanks everybody for your input and especially @msmoto for the extra work.

FlowtographyBerlin

@Vipmediastar_JZ: Just read my comment again, and just in case it came across as arrogant or something, it sure wasn't meant to be, I was just surprised, that's all. :-)

Ironheart

Are you still trying to solve the OS problem?

Vipmediastar_JZ

@flowtographyBerlin no wories
@ironheart yep. its still not resolved but will address at next time im at the office.