Intermediate Photoshop - Correcting Color Shifts

I'm sure a lot of us have come across color shifts in our photography, and they can be extremely frustrating.  This instructable is going to quickly go over why the shifts are there in the first place and then how to fix it in post. 

This method can be a little complicated, so take your time and try to practice, it will probably take a few tries to get it down.

You will need:

• Photoshop (or similar editing program)

**NOTE: All photographs used in this tutorial were shot and retouched by myself

First of all, before we get into correcting color shifts, we have to understand them.  Most cameras these days have an automatic white balance setting to control this issue, but everyonce in a while it can be inaccurate.

Color shifts are caused by different color temperatures in light, we call these "Kelvin temperatures."  Daylight has a Kelvin temperature of 5000, and is the most neutral you can get your photo to look. 

Have you ever photographed something in your house under a typical house bulb and the whole photo turned out orange or yellow?  That's because typical household lights have a Kelvin temperature of about 3000, which can look yellow, but because the human brain is so sophistocated, it corrects this to daylight temperature for us.  Tungsten and flourescent light bulbs can also have a similar effect, where we don't see the shift, but our cameras do.

Tungsten bulbs tend to have a magenta shift to them, while fourescent bulbs can turn a photograph green.  Yuck! 

In order to correct the color shift, we need to adjust both the highlights and the shadows in the image, as they both have their own separate temperatures.

First, you're going to need the Information tab open near your layers and adjustments palettes.  Click on the icon and you will see it pop up on the right side of the screen.

Select the Eyedropper tool from the tools palette, choose a highlight on your subject's face, (make sure it's not in an eyebrow or something with a lot of detail), and shift click that spot.  This will create an anchor point on your image that you can draw information from to fix whatever color it is that's out of order.  Do this again in a shadow area.  When you set the points, did you notice two new RGB menus show up in your info palette?

If you don't like where you put the point you can always remove them by holding shift + opt, (shift + alt on a PC), and click on the anchor. 

Once you have your points selected, you need to change the RGB menus in your info palette to CMYK menus, as this will be much easier to get the right correction.  Next to the list of percentages for RGB, there is an eyedropper icon.  Click the icon and scroll down to where it says CMYK color.

R - Red
G - Green
B - Blue

C - Cyan
M - Magenta
Y - Yellow
K - Black

Now we can use a "skin recepie" to find out which colors are off so we can adjust them in curves.

Now, here comes the slightly complicated part: the skin recepies.  Light, medium, dark and very dark skin tones are going to have different number combinations to bring them back to their natural state.  Below is a list of these combinations for each type of skin, (the ratios of these numbers are the same for the highlights, however the numbers may be a little bit lower).

Light

• C : 1/5 - 1/3 of M and Y 
• M : teens - lower twenties
• Y : teens - lower twenties
• K : none

Medium

• C : 1/5 - 1/3 of M and Y
• M : mid-twenties - lower thirties
• Y : mid-twenties - lower thirties
• K : none

Dark

• C : 1/3 of M and Y
• M : mid-thirties - lower forties
• Y : mid-thirties - lower forties
• K : none

Very Dark

• C : 1/3 of M and Y
• M : mid-forties - mid-fifties
• Y : mid-forties - mid-fifties
• K : 1 - 5%

Looking at these skin recepies and looking at your info palette, do you notice any particular number that is standing out from the others or where it's supposed to be?  That is the number we need to fix. In this particular photograph it looks like the magenta curve needs some help.

Go to your adjustment palette and select the "Curves" icon, this will bring up a curves adjustment layer.  Once you have that open, go to the curve that needs the most help.  In this case, we are going to go to the green curve as the opposite of green in the color wheel, (according to light, not paint), is magenta.  


*Tip: In curves, there is an overall RGB curve, which will adjust the brightness, a red curve, which adjusts red and cyan, a green curve, which adjusts green and magenta, and a blue curve, which adjusts blue and yellow.

In order to make sure we are adjusting the correct part of the curve, cmd + shift click, (ctrl + shift click on a PC), your anchor point on the photograph and a dot will appear on all three channels of the curves layer.  This is where we need to adjust our curve.

First we are going to adjust the highlights.  As I mentioned before, in this photograph, I needed to adjust the magenta, so I went to the green layer and pulled the curve until both the magenta and yellow were at 7% and the cyan was at 5%, (remember, I am only adjusting the green curve, the other numbers will move on their own with your curve, so keep an eye on them).

Looks much better already doesn't it?

Lets move on to the shadows.

It looks like the shadows need a little more help on this photograph so we'll have to adjust two curves layers.  Just as we did with the highlights, cmd + shift click your anchor point to get the dot on the curve.  I first adjusted the green curve as I did before, but in doing this, it affected the cyan curve, so after getting them as close as I could, (sometimes they don't exactly match, but don't worry about that, just get them as close as you can), I went to the red curve and adjusted it to get the skin recepie ratios back.

Ta da!

Now of course, not all photos are the same, this one was relatively easy to fix, so don't loose hope if you're having issues, just keep at it!  Practice makes perfect!