matching color from reference photo

[modelsfret]

If i have a reference photo where i like the skin tone, or background color. What would be the best way to try and match the color on my image -

[jklier]

Re: matching color from reference photo

If you are confident with seeing colors, you would mask the area, then add a curves layer and adjust individual channels until you find the match.

If you want to go more algorithmic at it, make a mask for the areas that need to get matched and save as a selection. Then create two hue/sat layers, one with a 'light' luminosity mask, the other one with the inverted mask, giving you separate control over highlights and shadows. To restrict the correction to a certain area, take the saved selection, invert it, and paint/fill black into the luminosity masks.

Sample the reference image shadows and highlights with a 15x15 averaged sample, and read the color in HSB mode (change the color mode of the picker in the info palette).

Now set two color sample points in the target image in the shadows and highlights, and also keep them in HSB mode. Then adjust the h/s/b sliders of the two correction layers until your sample points match the HSB values from the reference photo. Takes a bit of practice.

[klev]

Re: matching color from reference photo

Now set two color sample points in the target image in the shadows and highlights, and also keep them in HSB mode. Then adjust the h/s/b sliders of the two correction layers until your sample points match the HSB values from the reference photo. Takes a bit of practice.

That is unfortunately one of the better ways, although I prefer sets of masks combined with channel mixer. It's still quite rough due to the behavior of channel mixer in photoshop and its color management rather than the concept of mixing channel densities.

There is actually quite a bit of research out there on this topic, although I think it would be easier to incorporate in a raw processor than in a space like Adobe 1998.

[skoobey]

Re: matching color from reference photo

I agree with the above.

No, we are presuming that your and the reference image are similar when it comes to luminosity/density/overall feel. Check they visually by simply seeing both in B&W.

What I do is first mask everything out. Now, every area of color in the reference image needs a color point in hsb, and so does your image. Same brightness, same area (like 128 sky for example).

Now you go into the broad to specific area by area. First, I use curves to set the midtone color to be sort of the same and continue on with hue/saturation. Sometimes I use color balance. Then go into it locally. Just like jkiler explained.

Overall, it's not much different then when working on colors without an exact reference, tough part being that it has to match exactly.

[jklier]

Re: matching color from reference photo

Good point about the overall images being similar in luminosity and density.

There have been a number of website tools that utilize math analysis to determine the dominant color of an image as well as it's palette. One example is here: http://lokeshdhakar.com/projects/color-thief/. Especially in busy images it's sometimes harder to establish the dominant color in a precise fashion just by sight.

You could use this type of technique to compare the two images and see how similar they are. Possibly even going one step further and doing a global adjustment to the image to get them in the ball park before doing finer local adjustments with the techniques discussed above.

That said, I only know these tools from web coding techniques. Haven't seen a Photoshop action or plugin that can do the same type of color analysis, though it may very well exist.

[AKMac]

Re: matching color from reference photo

With skin tones, trying to exactly (numerically) match two different images, unless they are very, very similar, is usually just not going to work. The overall look of an image, particularly where skin tones are involved, is a very complex thing. I've rarely found the numerical approach helpful. In fact if you do eventually manage, after ages of tweaking, to match the shadow, mid tone and highlight values from a reference image, you will often find that it just looks wrong, and often ugly.
My advice is to trust your eyes.

[Shoku]

Re: matching color from reference photo

With skin tones, trying to exactly (numerically) match two different images, unless they are very, very similar, is usually just not going to work. The overall look of an image, particularly where skin tones are involved, is a very complex thing. I've rarely found the numerical approach helpful. In fact if you do eventually manage, after ages of tweaking, to match the shadow, mid tone and highlight values from a reference image, you will often find that it just looks wrong, and often ugly.
My advice is to trust your eyes.

I agree. We just did a layout for CK and the images they submitted were of the same model in different clothes against the same background. The skin tone in each was visually a little different, with one noticeably redder. We adjusted the appearance based on visual acceptability (reviewed by three artists). Only took a few minutes. Agonizing over specific numbers for highlight, mid-tone, and shadow values would have taken more time than was really necessary. As long as you understand what values equate with good skin tone the process can be very quick and simple.

Matching any color, other than a solid color, can be a real headache if you let the numbers dictate your results. In our business the proof of success is in the quality of the printed piece. Customers don't care about numbers - they only want it to look right.

All colors are influenced by the colors that surround them. If your target image is not exactly the same as your working image, the odds that the values need to be the same are probably very low.

[klev]

Re: matching color from reference photo

With skin tones, trying to exactly (numerically) match two different images, unless they are very, very similar, is usually just not going to work. The overall look of an image, particularly where skin tones are involved, is a very complex thing. I've rarely found the numerical approach helpful. In fact if you do eventually manage, after ages of tweaking, to match the shadow, mid tone and highlight values from a reference image, you will often find that it just looks wrong, and often ugly.
My advice is to trust your eyes.

That's partly because your eyes are very comparative. It can be useful to sample values, but those values should be a point of departure rather than a direct target.

[insmac]

Re: matching color from reference photo

Depending on the job I usually do it the simple way just by placing color picker markers on reference and target area and adjusting the target r/g/b curve output values from the reference point.

There are areas when you have to deliver a certain uniform colour across (say a lineup of eye shadows for a cosmetics ad) but with the fashion and people in overall I usually rely on an eyeball match within a few people.