correcting skin color

8/13/2019 Correcting Skin Color

1/15

Correcting Skin Color / Skin Tones: The Basics 6-2-2009For those who do any kind of color portraiture (whether traditional, photojournalistic, or otherwise), skin tonecorrection may well be the single most critical and most vexing - aspect of post processing. This the firstpost in a series of weekly tutorials will discuss the general principles and tools used in skin color correction.

Measuring Color and Taking SamplesWhere to begin? First, lets make sure we know how to measure the colors that are there. Go to Window>Info(or just press F8) to open up your Info Panel. Default readouts are RGB and CMYK, but if for some reason

you arent seeing the CMYK readout, choose Panel Options from the panels dropdown menu (top rightcorner), and choose Mode>CMYK under Second Color Readout.

Now, select your eyedropper tool (you can just press I on the keyboard). Right click anywhere on the image,

and when the menu pops up, select 55 (For a lower res picture) or 1111 (for a standard high res picture) tochoose the size of your sample.

Watch the CMYK values in the Info Panel change as you move your mouse across the picture; this is a goodway to quickly survey the colors in the image.

Next, shift+click on a few representative spots of skin, and take four color samples: two midtone areas, ashadow area, and a highlight area.

Good Sample Areas: Forehead (middle and side), Nose, Chin, Arm (assuming the body skin has the samecoloring as the facial skin - it doesnt always)

Bad Sample Areas: Specular highlights, very deep shadows, cheeks that are pinker than the rest of the skin,areas that have a color cast that differs from the rest of the skin

Now, in your Info Panel, you can see the CMYK values for each of your sample areas. Wait . Youreonly seeing RGB? Thats because youre working in RGB mode, and your color samples will, by default,reflect the mode that youre in. We want to see the CMYK values, so just click on the color sample dropper inthe Info Panel, and select CMYK; do this for each of your three color samples.


2/15

Skin Color by the Numbers: General Guidelines Great, so now know the CMYK values for your color samples. How do you know if they are correct?As a general rule, you want your skin midtones to be roughly as follows: 1) Cyan x 4 = Yellow2) Magenta + (0-10) = Yellow

For example, accurate values might be C:5/M:20/Y:23/K:0. Cs value (5) is the value of Ys value (20); andMs value (20) is within 10 points of Ys value (23). ( K is black and governs darkness. For most Caucasianskintones, that value will be at 0; as skintones get darker, the K value will increase. For evaluationpurposes, keep in mind that, like cyan, black reduces the skins brightness and pushes the color towardsgray). In practice (depending on age and ethnicity), Cyan may be anywhere from 1/3-1/6 the value of Yellow,and Yellow may exceed Magenta by as much as fifteen points. We can limit those ranges a bit as we start totalk more specifically about different ages and ethnicities; well get into that in a later post.

When can we expect correct tones to depart from those guidelines?

1) Cheeks: whether blushing or flushed naturally (or blushed due to makeup), the cheeks regularly (and quiteaccurately) will exhibit tones where magenta exceeds yellow. Thats fine and to be expected (and evenpreferred). Just make sure that more skin neutral areas dont share these higher magenta values.

2) Highlights: there are some spots that SHOULD have little to no cyan. Red - the opposite of cyan -corresponds directly to brightness in skin (i.e., if you tell me your brightness value when the HSB readout ispulled up, I can tell you the red value in RGB - one directly predicts the other). In short, when it comes to skin,highlights will have very low amounts of cyan.

3) Shadows: as you might expect, this is exactly the opposite of the guidelines for highlights (above);shadows exhibit a much higher ratio of cyan (generally 1/3-1/2 the value of yellow). Higher amounts of cyan(together with increased levels of black) are expected in the shadows, because adding cyan pushes skincolor towards gray (by bringing Red closer to the Green and Blue values), and shadows are more gray thanthe rest of the skin.

Across the board, the three most common problems that I see are for skin midtones (in this order): 1) Cyan at or greater the values of Magenta/Yellow;2) Magenta higher than Yellow; and3) (much less often) Yellow 11+ points greater than Magenta.


3/15

Skin Color Correction in ActionBefore we move on, lets do a quick review of the relationships between colors. Every image is comprised ofsix basic hues: red yellow, green, cyan, blue, and magenta. Take a look at the color wheel, and make note ofthe opposites: Red/Cyan, Green/Magenta, and Blue/Yellow. Because these pairs are opposite one anotheron the color wheel (below), when you push a pixel towards one of the colors, you necessarily shift that pixelaway from the other.

Back to skin. Youve measured your skin tones. You know your target color ratios. How do you make themmatch up? There are multiple tools in Photoshop that you can use to correct color; I occasionally useSelective Color and Color Balance adjustment layers. Here, however, were going to use my tool of choice Photoshops most powerful (and intimidating) tool: Curves.

There are four curves that you can work with when you open a Curves adjustment layer in RGB mode:1) RGB : A combination of the Red, Green, and Blue channels, this is your first stop when you want to adjustan images lightness, darkness, and contrast. Note that changes along this curve also affects your colorvalues uniformly across the Red, Green, and Blue channels.2) Red : This curve governs the red channel and controls the red and cyan in your image. Raise the curve toadd red / reduce cyan ; lower the curve to reduce red/ add cyan.3) Green : This curve governs the green channel and controls the green and magenta in your image. Raisethe curve to add green / reduce magenta ; lower the curve to reduce green/ add magenta.4) Blue : This curve governs the blue channel and controls the blue and yellow in your image. Raise the curveto add blue / reduce yellow ; lower the curve to reduce blue/ add yellow.

To adjust your curves, you need to move an anchor point on that curve. Every curve already has two anchorpoints they are the end points on the curve. By default, the values of those anchor points are 0 (thelower/leftmost end point) and 255 (the upper/rightmost end point). To add an additional anchor point,1) You can click directly on the curve itself, or2) You can use tools that allow you to click directly on the image and add an anchor point that corresponds tothe values where you clicked.


4/15

Now back to the skin Well use a great picture from Illinois photographer Jessica Gwozdz (JesG) to demonstrate a skin colorcorrection. Luckily, Jes has provided us a picture that is beautifully exposed and seems to have great whitebalance already set. Correcting exposure and white balance should always be your first step and will alwaysgreatly improve your overall image including your skin tones; sometimes, thats all you need to achieveperfect skin color.

Heres the original:

First, we take our color samples by selecting the eyedropper tool and shift+clicking on the desired areas. Imsampling midtones from the forehead and arm, highlights from the tip of the nose, and shadows from thearmpit. Im avoiding the babys beautiful rosy cheeks, because I already know that the magenta ought to behigher there, and that area of skin is not going to be representative of the values were trying to achieveoverall.

BTW, ignore the terrible colors in the screenshots; PrintScreen strips out my color profiles. Im only showingyou this so you can see my color samplers


5/15

I always focus on the midtones when I begin skin color correction; more often that not, the midtonecorrections also bring the highlights and shadows into line. With that in mind, lets take a look at the values ofthe midtone areas (Ive already changed my sample readouts to CMYK as described above):Sample #1: C:9/M:35/Y:49/K:0Sample #2: C:13/M:39/Y:53/K:0

Here, we can see that the yellow values are just too high. We have two options to correct this:1) We can bring down the yellow to within 10 points of magenta; or2) We can bring up the magenta to within 10 points of the yellow.

In this case, theres already a pretty good relationship between the cyan and yellow; in Sample #1, C (9) isroughly 1/5 the value of M (49), and in Sample #2, C (13) is roughly 1/4 the value of Y (53). Since our goal isto have cyan 1/3-1/6 the value of yellow (with being a good target in general), these look pretty good, buttheres room to bring the yellow down a bit. Why not just bring up the magenta? All things being equal, Iusually try to bring the curves up if I can (for less total CMYK color), but its really just a judgment call here,adding magenta is likely to work just as well, but Im going with the yellow. How do change yellow? With theblue curve (which governs blue and yellow in the image).

. To decrease yellow, we increase blue. First things first: create a Curves adjustment layer. We need ananchor point on the blue curve. To add an anchor point to the channels curvesi, select your eyedropper tool(it should already be active), and CTRL+Shift+Click on the desired color sample (Im using Sample #1).Look at your curves dialog. Nothing happened. Thats because you created an anchor point on the individualchannel curves (R, G, and B) not on the overall RGB curve. To see your anchor point, you need to selectan individual curve from the Curves dropdown menu

To decrease yellow, we increase blue. First things first: create a Curves adjustment layer. We need ananchor point on the blue curve. To add an anchor point to the channels curvesi, select your eyedropper tool(it should already be active), and CTRL+Shift+Click on the desired color sample (Im using Sample #1).Look at your curves dialog. Nothing happened. Thats because you created an anchor point on the individualchannel curves (R, G, and B) not on the overall RGB curve. To see your anchor point, you need to selectan individual curve from the Curves dropdown menu


6/15

Since I want to work with the blue curve, Im going to select that first.

With my blue curve selected and my new anchor point visible, all I have to do is click on that anchor point anddrag it straight down a bit. While youre dragging, watch the CMYK values (especially the yellow value)changing. Stop dragging when you achieve the desired value. Dont like the click-and-drag? You can alsoclick once on the anchor point, then just use your down arrow key to bring the Output values down (this ismy preferred method).

Sometimes, one curve adjustment is all it takes. Often times, however, adjusting one curve will throw off thevalues in other curves, and you have to make additional adjustments on the other curves. In this case, thevalues in our target sample (Sample #1) look pretty good with just the one adjustment.


7/15

Lets take a look at how the values may have shifted in the other Samples:

Sample #2: C:13/M:40/Y:45/K:0. This looks great. Cyan is almost exactly 1/3 of Yellow, which is fine, andYellow is 5 points higher than Magenta also fine.

Sample #3 (highlights): C:0/M:28/Y:30/K:0. This looks pretty good. Yellow is two points higher than Magenta,which is great. The Cyan is zero, and while we expect to see cyan really low in the highlights, a zero value*usually* tells us that Red is at 255 which means that the red channel has been blown out. Since it doesntlook like blowing it out in that spot is a big deal (the face looks perfectly exposed overall), were going to leavewell enough alone here.

Sample #4 (shadows): C:31/M:82/Y:100/ K:33. Okay here, here, cyan is roughly 1/3 the value of Yellow,and theres also a high amount of black, so the shadows are looking pretty gray (which is fine). Look atYellow, though not only is it 18 points higher than Magenta, but its off the charts. We need to bring thatdown a bit.


8/15


9/15

Heres the corrected image:

Heres the final set of curves / color samples:

When you make a major color adjustment, you may have to mask off non-skin areas. We dont have to dothat here, but I kind of like the warmer green background, so Ive brought it back just a bit for the finalproduct. Well cover how to do the necessary masks (including my secret perfect skin mask!) in anothertutorial.


10/15

Heres a before and after of the final color corrected image:

Close up:


11/15

Another Correction:Lets do one more correction. This picture comes from Washington photographer Rachel Noah (rachelnoah)and again were lucky to be working with perfect exposure and great white balance, which makes lifemuch easier.

Were going to go through this more quickly . First, set four color samples (midtones x2, highlights, andshadows).Again, ignore the crummy screen shot mess of colors - I just want you to see where Ive put thesamplers:

Take a look at the readouts:Sample #1: C:14/M:17/Y:20/K:0Sample #2: C:13/M:16/Y:19/K:0Sample #3: C:15/M:9/Y:14/K:0Sample #4: C:41/M:56/Y:65/K:21

You should notice immediately that the Cyan is much too high across the board. The relationship betweenMagenta and Yellow looks great (within 3-9 points, depending on the sample). How can this be corrected? Icreate a Curves adjustment layer, and then I use my eyedropper tool to shift+click on one of my midtonepoints (Im using Sample #1). Now I have a new anchor point on each of my R, G, and B Channel curves. Tobring down the Cyan, we pull up on the red curve.


12/15

Take a look: Now I have cyan coming in at exactly 1/3 the value of yellow, but the subject is really looking red or is she looking magenta?

Taking a look in the Info Panel, we can now see that, in moving the red curve up, weve also increased themagenta value.

Easy enough lets drop the magenta value. Select the green curve and click on the anchor point, then pressthe up arrow (or drag the point upwards) to increase the green / decrease the magenta.

Things are looking much better, both visually and in terms of the numbers:


13/15

Lets evaluate the new readouts:Sample #1: C:6/M:17/Y:21/K:0. Looks great!Sample #2: C:6/M:16/Y:20/K:0. Looks great!Sample #3: C:7/M:10/Y:14/K:0. Cyan is coming it at 1/2 the value of Yellow. Id like to see that lower.Sample #4: C:30/M:59/Y:70/K:21. Looks great! Cyan is coming in at between 1/3 and 1/2 the value of Yellow,which is fine in the shadows.

Okay, so were just gonna drop the cyan a bit in the highlights (Sample #3). Back to the red curve. Create anew anchor point by using the eyedropper tool and Shift + Clicking on the highlight point (Sample #3).


14/15

Well, heres a dilemma: the red point here is literally RIGHT NEXT TO the red point for the midtone sampler(highlight cyan value is 7 / midtone cyan value is 6). If I move it, Im going to be adjusting the cyan/red in themidtones as well, and we already know that those look perfect.

There are a couple of ways to approach this:1) Leave it.2) Create a new adjustment layer, mask off all of the skin except for the highlight problem area, and correctthe color in that area separately.

Im going with option #1. I think the color already looks great, and sometimes its best to leave well enoughalone. I also like the brightness of the wall, so Im not even going to mask anything off this time so heresthe final product (before and after):


15/15

Close up:

Whew! Thats it! More next week (though it wont be nearly as long because now you have the basics!).

Let me know if you have questions or are confused by some aspect of this!

correcting skin color

Documents