While most people do shoot RAW and can tinker their WB by GUI sliders from their software (such as Lightroom), sometimes, it's beneficial to know how to do it from scratch as well.

Of course, it'll be best to make sure your WB is accurate to begin with, but the world is not perfect, hence image editing software was created.

Anyway...

Here's the original image with severe color cast from the tungsten light in the room shot with AWB setting.

http://i9.photobucket.com/albums/a69/theveed/origwb.jpg


We'll be using CMYK to reference our skin tone correction. The basis is, light skin should roughly have a ratio of:

M+Y values = 5 times the C value.

Before you panic about the equation, it's really quite simple. If your Cyan value is 10%, your Magenta and Yellow value should add up to roughly 50%. Depending on the obvious color cast, either the Magenta or Yellow value will be higher.

It's also worth noting that lighter skin tones will have a smaller ratio, usually a M+Y = 3x C instead of 5x C... Conversely, dark skintones will have a higher ratio.

These are just guideline figures.

Here we go.

1) Open your image and select your Color Sampler tool. I prefer to pick a larger sampling area (CS2 only allows up to 5x5, I think CS3 can go much higher).

http://i9.photobucket.com/albums/a69/theveed/1.jpg


Click on a non-reflective part of the face that you want to use as a reference point. I prefer the middle cheek, forehead, chin, or nose bridge in most cases. Here, I chose the area between the eyes.

http://i9.photobucket.com/albums/a69/theveed/2.jpg

I also sampled the background wall as I know that the wall is off-white with a hint of pink. If I can get that close to actual, then I know I'm close to correcting the skin as well.

2) Now look at the INFO palette, you'll need to look at the CMYK values, so click on the little airbrush icon and choose CMYK Color from the drop-down list.

http://i9.photobucket.com/albums/a69/theveed/3.jpg


3) Our first sampling point is the skin, you'll see the values in the red box. You'll notice that the Y-value is really high, so we need to tackle that first.

http://i9.photobucket.com/albums/a69/theveed/4.jpg


Note the right sampling point of the wall. Since I know the wall is near-white, the number should reflect on the high-200 value.. The blue channel is obviously causing some color cast onto the wall.

So based on those alone, we know that we have to mainly fix the Yellow channel first, then adjust the others in small increments.

(Con't)

4) The opposite color of yellow is obviously blue. So we open a Curves adjustment layer and change the Channels to Blue (instead of RGB). Use the color dropper to click on the sampled spot and it'll display where that sampled color is on the graph (you'll see a square appear along the line).

http://i9.photobucket.com/albums/a69/theveed/5.jpg


Drag that line upwards (adding blue values) to reduce the yellow value. You'll see that most of the yellow color cast is gone. The image looks more "normal" now, but we still see some pinkish cast, so we'll need to look at the red channel next.

5) Now select the RED channel from the drop-down list and click the sampled point again to see where to adjust the curve. Once you've found the spot, drag the curve DOWNWARDS to reduce red value. This'll reduce the Magenta values. Move it until you get the rough ratio above (5xC=Y+M).

http://i9.photobucket.com/albums/a69/theveed/6.jpg


Note that you don't have to get it exact. Read the top of this page.

6) Finally, choose "RGB" from the Channels drop-down list and make a simple "S" constrast curve to complete the correction.

http://i9.photobucket.com/albums/a69/theveed/finalwb.jpg


Hope you guys found this useful.

-Dave

wow thanks for sharing..:)

This helps if your monitor isn't calibrated heheheh.

This is really informative TFS sir david!

Is this similar to this?
http://www.ledet.com/margulis/PP7_Ch02_ByTheNumbers.pdf

Hmm, first time I've seen that PDF, thanks for the link :)

I've learned the steps above from a video I borrowed from the library...

I guess I just wasted my time typing and screen-capping hehe.

Wow! Excellent tip!

How about when you wanna get that copper tan look?

We'll try another thread on that hehe... Not really good at it coz it's not what I usually do (B&W), but I'm sure if you start a thread, the experts here will point you the right way (psst, Ronnel Cuison hehe).

Cool! Very useful info. TFS!

saved for future reference. thanks david!

wow, thanks for sharing guyz!

wow, tfs david. this is very helpful. :)

i see this one also at photoshopkillertips.com, if i'm not mistaken. the instructor was dave cross the canadian guy?! correcting colors by the numbers. he uses the eye dropper tool pointing to white, black and neutral gray area. i couldn't remember the technique though. :)

Jo Avila taught me (thru his class) how to work on tonal correction thru Color by the Numbers. I saw the same workflow upon reading Lee Varis' "Skins" book I bought from Amazon and surely a very helpful workflow.

Hi David!

I saw a similar Color by Numbers via a Lynda.com tutorial but the formula is different. Formula is C=1/3 or 1/5 of M (depending on skintone); Y is a bit higher than M; then K = 0.

Usually starts by pushing K to 0 via Curves adjustment composite RGB, then addresses the Yellow (via the Blue) then the Cyan (via the Red)

What do you think?

RC

RC: Yes, I've borrowed that CD-ROM as well before, I think the author there mentioned that those values are more appropriate for Caucasian skin... I'm sure he's more correct hehehe, will try to borrow that CD again tomorrow from the library.

Thanks very much for this David!

Arnel

Nice tutorial David! TFS. However, do I have to set the mode of my Image to CYMK to be able to use this workflow (my camera mode is AdobeRGB1998)?

Cheers!

Jek

Nice tutorial David! TFS. However, do I have to set the mode of my Image to CYMK to be able to use this workflow (my camera mode is AdobeRGB1998)?

Cheers!

Jek

Your camera settings and the tutorial are two different things. You don't need to convert to CMYK since the Info Palette reads RGB and CMYK already. Adobe RGB is a color space and has little to do with the whole tutorial.

Cool. Thank Nino for the clarification. I'm learning a lot here. :Grin:

Before adjusting skin tones, it's a good idea to color correct the overall image first. Removing an overall color cast, such as the OP's image has, will give you a better starting point on the skin tones.

Here are some video tutorials on using CMYK values to adjust skin tones:

http://www.lynda.com/home/Player.aspx?lpk4=46080

http://www.lynda.com/home/Player.aspx?lpk4=46081

http://www.lynda.com/home/Player.aspx?lpk4=46082

http://www.lynda.com/home/Player.aspx?lpk4=46083

http://www.lynda.com/home/Player.aspx?lpk4=46084

http://www.lynda.com/home/Player.aspx?lpk4=46085

http://www.lynda.com/home/Player.aspx?lpk4=46086

http://www.lynda.com/home/Player.aspx?lpk4=46087

http://www.lynda.com/home/Player.aspx?lpk4=46088

Before adjusting skin tones, it's a good idea to color correct the overall image first. Removing an overall color cast, such as the OP's image has, will give you a better starting point on the skin tones.

Here are some video tutorials on using CMYK values to adjust skin tones:

http://www.lynda.com/home/Player.aspx?lpk4=46080

http://www.lynda.com/home/Player.aspx?lpk4=46081

http://www.lynda.com/home/Player.aspx?lpk4=46082

http://www.lynda.com/home/Player.aspx?lpk4=46083

http://www.lynda.com/home/Player.aspx?lpk4=46084

http://www.lynda.com/home/Player.aspx?lpk4=46085

http://www.lynda.com/home/Player.aspx?lpk4=46086

http://www.lynda.com/home/Player.aspx?lpk4=46087

http://www.lynda.com/home/Player.aspx?lpk4=46088




These tutorials are wonderful! Thanks for sharing!

TFS guys. Very helpful thread here to better understand skin tone color correction on both RGB and CMYK color spaces. :)

TFS guys. Very helpful thread here to better understand skin tone color correction on both RGB and CMYK color spaces. :)

Just note that in the tutorials I linked to, you're not working in CMYK. You remain in RGB but monitor CMYK values in skin tones. Don't convert from RGB to CMYK. Big mistake. :(

Hey thanks op for sharing. i find this useful :)

http://photos-a.ak.fbcdn.net/hphotos-ak-snc3/hs220.snc3/22772_331801692393_731007393_5249853_5399936_n.jpg

Yeah very useful stuff, thanks David

Joms: Wow, that's a huge shift :D Good job

thanks for the sharing

Before adjusting skin tones, it's a good idea to color correct the overall image first. Removing an overall color cast, such as the OP's image has, will give you a better starting point on the skin tones.

Here are some video tutorials on using CMYK values to adjust skin tones:

http://www.lynda.com/home/Player.aspx?lpk4=46080

http://www.lynda.com/home/Player.aspx?lpk4=46081

http://www.lynda.com/home/Player.aspx?lpk4=46082

http://www.lynda.com/home/Player.aspx?lpk4=46083

http://www.lynda.com/home/Player.aspx?lpk4=46084

http://www.lynda.com/home/Player.aspx?lpk4=46085

http://www.lynda.com/home/Player.aspx?lpk4=46086

http://www.lynda.com/home/Player.aspx?lpk4=46087

http://www.lynda.com/home/Player.aspx?lpk4=46088

Thanks for this!! :)

TFS! very informative :)

Now I know how to treat the photos that I take whenever I am inside Shakeys! :Grin: Thanks a lot maestros!

Just a note, you will need to convert to CMYK if you plan to pass your work to printing presses (if you laid out a pic for a poster, etc). This is due to Press machines working in plates in CMYK.

Wow, wonderful tutorial. Silly question. How do we take into consideration the skin tones of Caucasians and Blacks? Do we use different adjustment settings?