Color Correction

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There are at least 5 different (and probably a lot more) color correction techniques built into Photoshop, including ...

Auto Color
The Gray Point Eyedropper
Average
Color Balance
Variations

This can be a really big deal when the lighting conditions did not match the white balance of the camera and you have a really nasty looking image or you've scanned a really old image that has an awful color cast.

Some of the color correction techniques are really easy and work well under some conditions while others seem to defy any logic and may cause a tad of frustration.

This tutorial will highlight one of the five (Average) plus a variation of another one (The Gray Point Eyedropper).

With Auto Color correction you simply click a couple of buttons on a curves or levels adjustment layer.

Color Balance is a whole other thing and very fiddly. This is an adjustment layer and most of the time when I have tried to use it I have ended up muttering unkind things about the dialogue and hitting the Cancel button.

Variations is the easiest. Simply go to Image > Adjustments > Variations and fiddle around with a few adjustments and hopefully you will get what you want.

OK - let's look at the Average method of color correction first - you are going to love this one ...

Average Color Correction

Using the Average Filter is surprisingly easy!

Duplicate the Background layer (the one with the nasty color cast).

Go to Filter > Blur > Average (on the Background Copy). This will fill the layer with the overall color that makes up the image.

Press Ctrl-I (Windows) or Cmd-I (Mac) to invert the color. The result is the exact opposite of the one causing the color cast.

Set the Blend Mode for the Background Copy layer to Color and then start lowering the Opacity of the Background Copy layer while you watch the image. At some point the cast will disappear and you will have a nicely balanced image - maybe!

It is a very effective method for sure. Here are a couple of samples with commentary ...


The original Image which was scanned from a print.	The image was shot on a subway platform with the white balance set to Daylight.

The color on the left is the predominant color of the image and the one on the right is the inverse after applying Blur > Average and changing the Blend Mode to Color.	The greenish hue on the left is the predominant image color and the bluish hue on the right is the result of applying Blur > Average and changing the Blend Mode to Color.

The Opacity was lowered until the image looked more natural (about 39% Opacity) but the image is flat and requires further adjustment.	The Opacity of the Average Filter layer was lowered until the color cast was eliminated (around 49% Opacity). The image can use some additional adjustment.

A Levels Adjustment Layer was added to increase brightness and then a Curves Adjustment Layer to increase Contrast.	After the Average Filter Adjustment was made all this image needed was some brightening with a Levels Adjustment Layer.

The final image - much better now that the annoying reddish color cast is gone.	The final image which is an improvement over the original with the greenish color cast.

Now isn't that easy?

This method of color correction will also work with Photoshop Elements!

Video

Color Correcting With
The Average Filter

White - Black - Middle Gray
Color Correction

You know something - I have no idea what this technique is called so I'm calling it the white - black - middle gray method of color correction.

This is the image I am using for this tutorial. It is some children's artwork on the wall of an elementary school gym. The overall color cast is kind of yellow because of an incorrect white balance setting.

color corrections gym original

This image needs some maintenance right away - it is hard to look at the dark line at the top and the benches at the bottom with their silly angles - let's use the Perspective Crop to fix it ...

Ah - that's better - now let's get going with this technique ...

This technique will use the totally mysterious Threshold Adjustment Layer plus you will learn some neat little Photoshop tricks that can be used in lots of places.

Open your image and duplicate it if you wish - although you may not want a duplicate of that nasty color cast.

Create a Threshold Adjustment Layer. This is what it will look like ...

color correction threshold

Drag the little slider in the center all the way to the left until the image turns pure white.

If there are still some black dots on the screen then go to the next step.

If not then use the Up arrow key or drag the slider back to the right until you see the very first black dot - and then stop.

This is the blackest part of your image and you are going to put a marker on one of the dots to be used later.

Remember I said you were going to learn some neat little Photoshop tricks - here they are! The little dots are far too small to accurately mark so you need to zoom in without leaving the Threshold Adjustment dialogue - and the Zoom tool won't work with a dialogue open.

Move the cursor onto the image and it changes to an Eyedropper. Now press ...

To Zoom In ...

Space + Ctrl (Windows)
Space + Cmd (Mac)

To Zoom Out ...

Space + Alt (Windows)
Space + (Mac)

The cursor changes to the Zoom tool - isn't that neat?

Now all you have to do is draw a selection over one of the little black dots to zoom in. Keep zooming until the little black dot becomes a big black dot - like this ...

The next step is to mark one of the little black dots. When you move the cursor off of the Threshold dialogue it changes to the Eye Dropper.
color correction black dot

Press and hold the Shift Key and Tap (with a pen) or left click one of the little black dots. A marker will be placed on the black dot - the darkest part of the image has been selected.

Now drag that little slider all the way to the right, turning the image totally black. Press the down arrow key of move the slider to the left and when you see the first white dot appear - stop.

Zoom in on one of the little white dots using your new trick, press and hold the shift key and place the second mark on the white dot ... color correction white dot

. Now you have the whitest part of the image selected.

Cancel the Threshold dialogue because you don't need it now - it has done it's work!

The two little markers may not be visible but don't worry - they will show up when they are needed.

The final step is to find Middle Gray on the image which is a bit more complicated.

Here's how to find the elusive Middle Gray ...

Create a new blank layer above the Background Layer.

Fill this layer with 50% gray - Edit > Fill > 50% Gray.

Change the Blend Mode of this layer to Difference. The image will look really weird but that is OK.

Add a Threshold Adjustment Layer and drag the little pointer all the way to the left, turning the image white.

Start moving the pointer to the right and stop as soon as the first black dot appears.

Zoom in in the black dot and place the third maker by pressing and holding the Shift key and left clicking or tapping with your pen.

Cancel the Threshold Adjustment Layer.

Drag the new layer into the Trash so all you are left with is the original Background.

That is the set up and what you have now is a marker on a pure white pixel, a marker on a pure black pixel and a marker on a middle gray pixel.

Create a Levels Adjustment Layer ...

The Eyedroppers in the Levels Dialogue are outlined in red.

The Left Eyedropper is the black point.
The Right Eyedropper is the white point.
The Middle Eyedropper is the Middle Gray point.

Find the marker you placed on your image for the black point - it has the number 1 right next to it. Click on the Black Eyedropper (the left one) and then click exactly in the middle of the Black Point Marker.

Find the marker you placed on the image for the white point - it has the number 2 right next to it. Click on the White Eyedropper (the right one) and then click exactly in the middle of the White Point Marker.

Find the marker you placed on the image for the middle gray point - it has the number 3 right next to it. Click on the Middle Gray Eyedropper (the middle one) and then click exactly in the middle of the Middle Gray Point Marker (this one may make an enormous difference in the image).

Click OK and that's it - you are done (other than getting rid of the little markers).

Select the Eyedropper tool and locate the markers. One by one place the Eyedropper over the points, press and hold the Shift key and drag the points off of the image.

Here is the final color correction image ...

That yellow cast is gone and the image is much brighter now.

There you go - two really neat and useful methods to do a color correction on those images that need it.