Krunoslav-Stifter wrote:
info panel you should be able to see what is the; "relative amount of blue in a sample group of pixels" ...but this is only if I'm understanding you correctly and that is in fact what you want to do.

+1
info palette can give you RGB, CMYK or HSB numbers

Jeffery Williams wrote:
patch #1: RGB is 160, 125, 98
patch #2: RGB is 227, 190, 163

Jeff

they are almost identical color (1 degree difference)
they are vastly different in saturation and brightness

usually values are stated as R-G-B, instead of the other way around

Jeffery Williams wrote:
My retoucher is pointing out some patches of an image that appear to have a color cast. I wanted to use diff raw conversions and compare the amount of blue in these patches relative to other areas in the same image where we don't "see" the blue.

patch #1: RGB is 160, 125, 98
patch #2: RGB is 227, 190, 163

Which has more blue & why? Don't say #2 because of the 163 value. These are absolute values, meaning it is higher because the exposure/brightness is higher. That's what I mean by relative.

thanks,

Jeff

The red channel is the dominant color and the blue channel is contributing the least. Based on those numbers alone and without knowing which rgb color space you're in, I would guess there is no blue but would think that color would be like a reddish orange.

I would recommend setting up your info panel to read lab is that is the most straight forward way of comparing color. To measure blue, simply look at how negative the B channel is. 0 will be completely neutral (i.e. black, white or grey), while something like -5 has a very slight blueish cast and something like -30 will be very blue and so on. Positive numbers in the B channel on the other hand will be yellow. Positive numbers in the A channel are magenta and negative numbers are green.   

You can use rgb but if you're going by the numbers, you have to take into account how the other numbers will affect that patch of pixels as well as what rgb space you're in (i.e srgb vs argb). Likewise you can use hsb but you have to know what range of hue values correlate to blue before you can look at saturation. Lab just tells you how much of what color you have. Very simple and easy to read once you understand how it's set-up.

Ruben Vasquez wrote:

The red channel is the dominant color and the blue channel is contributing the least. Based on those numbers alone and without knowing which rgb color space you're in, I would guess there is no blue but would think that color would be like a reddish orange.

I would recommend setting up your info panel to read lab is that is the most straight forward way of comparing color. To measure blue, simply look at how negative the B channel is. 0 will be completely neutral (i.e. black, white or grey), while something like -5 has a very slight blueish cast and something like -30 will be very blue and so on. Positive numbers in the B channel on the other hand will be yellow. Positive numbers in the A channel are magenta and negative numbers are green.   

You can use rgb but if you're going by the numbers, you have to take into account how the other numbers will affect that patch of pixels as well as what rgb space you're in (i.e srgb vs argb). Likewise you can use hsb but you have to know what range of hue values correlate to blue before you can look at saturation. Lab just tells you how much of what color you have. Very simple and easy to read once you understand how it's set-up.

The b channel is showing 26-29 in the questionable areas. The other areas are about the same. So, we can't count on eye's is the lesson I am getting. Working in ARGB.

Jeffery Williams wrote:
My retoucher is pointing out some patches of an image that appear to have a color cast.

If a (possible) color cast is the problem, I think you're going at it the wrong way. You need to find what should be true whites, blacks, or neutral grays in between, and check those RGB values.

EDIT: If those are skin tones that you posted the values for, then they look to me like they have too much yellow (too little blue) in them.

Jeffery Williams wrote:
The b channel is showing 26-29 in the questionable areas. The other areas are about the same. So, we can't count on eye's is the lesson I am getting. Working in ARGB.

That's right. Regardless of if the monitor(s) is calibrated and you have the proper viewing conditions, our eyes are easily deceived and can't be trusted to make objective, color critical decisions which is where the numbers are particularly useful.

Our eyes are awfully good figuring out what looks good or not though. Those areas are pretty well saturated with yellow, the only question now, is that to your liking?

Peano wrote:

If a (possible) color cast is the problem, I think you're going at it the wrong way. You need to find what should be true whites, blacks, or neutral grays in between, and check those RGB values.

EDIT: If those are skin tones that you posted the values for, then they look to me like they have too much yellow (too little blue) in them.

The issue is that patches in the image, not the entire image, "appear" to have a blue tint. My first reaction was to prove this true or false. I now believe our eyes are deceiving us. An illusion if you will. Yes, skin tones.

Jeffery Williams wrote:
I now believe our eyes are deceiving us. An illusion if you will. Yes, skin tones.

Not sure if you can download and watch this, but I think it might confirm your suspicions?

http://dl.dropbox.com/u/28508998/Jeff/W … yesMAC.zip

Jeffery Williams wrote:
My retoucher is pointing out some patches of an image that appear to have a color cast. I wanted to use diff raw conversions and compare the amount of blue in these patches relative to other areas in the same image where we don't "see" the blue.

patch #1: RGB is 160, 125, 98
patch #2: RGB is 227, 190, 163

Which has more blue & why? Don't say #2 because of the 163 value. These are absolute values, meaning it is higher because the exposure/brightness is higher. That's what I mean by relative.

thanks,

Jeff

By simple % calculation, the % blue in Patch #1 is 25.59, the % blue in Patch #2 is 28.10.  #2 has 9.8% more blue than #1.

Is that what you you want to know?

Rich Images wrote:

By simple % calculation, the % blue in Patch #1 is 25.59, the % blue in Patch #2 is 28.10.  #2 has 9.8% more blue than #1.

Is that what you you want to know?

That's what I did but didn't know if was a valid measure.

Peano wrote:
Perception is reality. Don't get hung up on numbers.

Oh great, now I have to use my eyes?

Jeffery Williams wrote:
Oh great, now I have to use my eyes?

Mother Nature has a way of getting the last word . . .

Krunoslav-Stifter wrote:

Not sure if you can download and watch this, but I think it might confirm your suspicions?

http://dl.dropbox.com/u/28508998/Jeff/W … yesMAC.zip

downloaded fine, ~20 mb file but got an error when running, "server something"

Jeffery Williams wrote:
downloaded fine, ~20 mb file but got an error when running, "server something"

Yeah, that's weird. Some pople have issues others don't, not sure why. Will upload again. Wait.

OK, Try now.

http://dl.dropbox.com/u/28508998/Jeff/W … r-Eyes.zip

Krunoslav-Stifter wrote:

Yeah, that's weird. Some pople have issues others don't, not sure why. Will upload again. Wait.

OK, Try now.

http://dl.dropbox.com/u/28508998/Jeff/W … r-Eyes.zip

same issue

Jeffery Williams wrote:

same issue

I have no idea why that is, only video that some people can play without a problem, including me and for some without any explanation it's a problem. Hmmm. I have exported, encoded the entire video again and uploaded it. Hope it works.

http://dl.dropbox.com/u/28508998/Jeff/W … r-Eyes.zip

Jeffery Williams wrote:
Here's an update and the image

Notice the blue tint in the chest area and the C % numbers. I am not sure what this is really telling us. Should the C % be pretty constant throughout the skin? A quick test on another image say's no. Again, the issue is not that the skin tone is bad or not color/WB corrected. Instead, it is that parts of the chest area appear to have a [more] blue tint than the rest of the skin. Are the C % numbers proof of this? If yes, then is this something to worry about? What causes it?

Image taken with D800, raw conversion with capture nx2, argb color spare, ab lights, wb=flash, wb correction using gray card. No ambient light.

I don't see a blue tint no. What I see is that the chest is less saturated especially in comparison to her arm so the numbers don't surprise me. Red is the opposite of cyan so the more red you have (like her arm), the lower the cyan percentile will be where as her chest has less red in it so the percent cyan is higher. There are natural variations in skin tone (both in luminance and in color), throughout the body and that of course, is going to vary from person to person.

Ruben Vasquez wrote:

I don't see a blue tint no. What I see is that the chest is less saturated especially in comparison to her arm so the numbers don't surprise me. Red is the opposite of cyan so the more red you have (like her arm), the lower the cyan percentile will be where as her chest has less red in it so the percent cyan is higher. There are natural variations in skin tone (both in luminance and in color), throughout the body and that of course, is going to vary from person to person.

Thank you Ruben

Jeffery Williams wrote:
Notice the blue tint in the chest area and the C % numbers. I am not sure what this is really telling us. Should the C % be pretty constant throughout the skin?

It isn't telling you anything. You're over-analyzing. Open a selective color adjustment layer and set it like this:



Invert the mask and paint white with a soft brush, 10% brush opacity, over the parts that look a tad blue to you.