Photo Retouching - - Color Replacement problems-- Photoshop CS2

Rob1960 · #1 09-25-2007, 08:22 AM

Can someone tell me what I'm doing wrong?

I'm encountering a lot of difficulty getting accurate shades of color when using the color replacement tool. My specific project today involves changing an object in a photo from light brown to dark blue. I'm trying to reproduce a very specific shade of dark blue from another part of the same photo. But the result keeps coming out as an unacceptable shade of light blue. Any help greatly appreciated. Thanks.

pixelzombie · #2 09-25-2007, 08:37 AM

don't use that tool, make an adjustment layer and start from there...i will usually start with either a color fill or channel mixer adj. layer depending on how big of a color move i need...

edgework · #3 09-25-2007, 09:43 AM

Quote:

Originally Posted by Rob1960

Can someone tell me what I'm doing wrong?

I'm encountering a lot of difficulty getting accurate shades of color when using the color replacement tool. My specific project today involves changing an object in a photo from light brown to dark blue. I'm trying to reproduce a very specific shade of dark blue from another part of the same photo. But the result keeps coming out as an unacceptable shade of light blue. Any help greatly appreciated. Thanks.

The problem with both color layers and channel mixer, or curves, or selective color, is that no matter what you do, you're pretty much stuck with the original light/dark ramp, apart from the colors.

The only tool that's useful for this kind of thing is the gradient map. The nice thing about it is that it totally overwrites the underlying colors, but retains the grayscale ramp as a kind of category system for mapping the new colors from your gradient. This gives you complete control over the tones of not just the target color, and where to position it in the range of values, but also the shadows and highlights.

Set a Gradient Map adjustment layer, open the edit gradient window and replace the default colors with your target color in the center, a darker version to the left and a lighter version to the right. Slide them back and forth to determine where they best match the detail in the underlying image. If you need darker shadows or lighter highlights, add additional keys to the left and/or right.

It's a lot easier to get by simply experimenting, than it is to explain it. Trust me, it's the best color shifting tool that no one uses.

cricket1961 · #4 09-25-2007, 11:08 AM

Couldn't agree more Edgework. Its one of my main tools.

Chris

mistermonday · #5 09-25-2007, 11:08 AM

Rob, as other members have pointed out, the color replacement tool is not what you want to use becuase it preserves luminosity. The Gradient map is one potential as Edgework has pointed out. However, I prefer to use an accurate but simple Curve adj layer. I convert the image to LAB color and make a selection of the area I want to recolor. Note the colors of the color you want to change to. Adjusting the L channel curve will reduce the luminosity and the A and B values will set the color. A tweak of the composite curve can adjust the overall tone to what you need it to be.
Regards, Murray

edgework · #6 09-25-2007, 12:43 PM

Quote:

Originally Posted by mistermonday

Rob, as other members have pointed out, the color replacement tool is not what you want to use becuase it preserves luminosity. The Gradient map is one potential as Edgework has pointed out. However, I prefer to use an accurate but simple Curve adj layer. I convert the image to LAB color and make a selection of the area I want to recolor. Note the colors of the color you want to change to. Adjusting the L channel curve will reduce the luminosity and the A and B values will set the color. A tweak of the composite curve can adjust the overall tone to what you need it to be.
Regards, Murray

I'm a big advocate of using LAB for severe color shifts of all kinds. I agree that it would be possible here, except that LAB is never good for fine precision. (Try to pull heat out of face shadows without turning everything else screwy). (Okay, maybe with Blend-If sliders). But that just makes my point. It's complicated and tricky in LAB. Whereas The gradient map is EXACT. And easy. But hey, it's the result that pays the rent and we get our results with the tools we're familiar with.

I assume when you say "tweak of the composite curve" you mean when you convert back to RGB, since there is no composide curve in LAB, and you never use the composite curve in CMYK, of course.

Daviskw · #7 09-25-2007, 01:07 PM

Hi there

Check the below link out .... it may help.

http://forums.dpreview.com/forums/re...ment+tool&qf=m

edgework · #8 09-25-2007, 03:23 PM

Even if the Color Replacement tool can be used to override luminosity it still is inadequate, since it replaces ONE color with One different color. You want something that will replicate the shadow/highlight profile of the object being changed. That means a range, not just one.

mistermonday · #9 09-25-2007, 03:50 PM

Edgework, LAB is definitely not the solution for many thing but it is for some. Getting precision colors is one of them. Separating colors with precision is another. The gradient map is fine for color replacement but I find that pinning the darkest point to be changed setting 3 values (1 per channel), gets me to the end result faster than with a gradient map. It's like you say - whatever tools we are familiar....
Regards, Murray

pixel_monkey · #10 09-25-2007, 04:23 PM

Quote:

Originally Posted by Rob1960

Can someone tell me what I'm doing wrong?

I'm encountering a lot of difficulty getting accurate shades of color when using the color replacement tool. My specific project today involves changing an object in a photo from light brown to dark blue. I'm trying to reproduce a very specific shade of dark blue from another part of the same photo. But the result keeps coming out as an unacceptable shade of light blue. Any help greatly appreciated. Thanks.

Try this, convert your file to LAB and invert both the A and B channels. That should give you a blue color with shadow and highlight intact. You can easily adjust it to whatever shapes of blue you desire from there.

Markzebra · #11 09-25-2007, 04:58 PM

The gradient map works, try it! Doesn't preserve subtle colour shifts though. In my opinion though, the channel mixer is generally the tool for massive color changes, where Luminosity AND colour need to change. Less destructive.

pixelzombie · #12 09-25-2007, 06:37 PM

i'll have to try the gradient on a problem image i worked on last year...

mayday · #13 09-26-2007, 08:12 AM

I'm a big advocate of using LAB for severe color shifts of all kinds. I agree that it would be possible here, except that LAB is never good for fine precision. (Try to pull heat out of face shadows without turning everything else screwy). (Okay, maybe with Blend-If sliders). But that just makes my point. It's complicated and tricky in LAB. Whereas The gradient map is EXACT. And easy. But hey, it's the result that pays the rent and we get our results with the tools we're familiar with.

Do you guys ever use the gradient map to get consistent skin tone colours, then mask out in a adjustment layer mask? Then you get not colour shift problems?

edgework · #14 09-26-2007, 09:07 AM

Quote:

Originally Posted by mayday

Do you guys ever use the gradient map to get consistent skin tone colours, then mask out in a adjustment layer mask? Then you get not colour shift problems?

If you choose your samples in the gradient carefully (preferably from the actual image, unless it's just too screwed up,) and use a sufficient number of samples (maybe ten or so) you can get extremelyi realistic results, except, of course, you'll lose rosy cheeks and lips need to be masked out (or given their own map). I wouldn't use it as a standard color correcting tool, by any means, but in the context of your question, yes, it will equalize your skin tones throughout the value range. This isn't necessarily a means to realistic skin, by the way; skin varies in hue, saturation and value from one point to the next and needs careful modulation to keep it looking natural.

mayday · #15 09-26-2007, 09:27 AM

edgework]If you choose your samples in the gradient carefully (preferably from the actual image, unless it's just too screwed up,) and use a sufficient number of samples (maybe ten or so) you can get extremelyi realistic results, except, of course, you'll lose rosy cheeks and lips need to be masked out (or given their own map). I wouldn't use it as a standard color correcting tool, by any means, but in the context of your question, yes, it will equalize your skin tones throughout the value range. This isn't necessarily a means to realistic skin, by the way; skin varies in hue, saturation and value from one point to the next and needs careful modulation to keep it looking natural.[/quote]

Thanks edgework, What do you find to be the best method to equalize skin if its gone a bit off in some areas, I find sometimes after D&B you can get a colour shift