Through some email discussions with Margie, I offered to do a curves color correction tutorial, based on instruction from Moose Peterson (
www.MoosePeterson.com ~ I highly recommend his blog), and Ben Willmore (
www.digitalmastery.com).
The photo example I am using was restored a long time ago but a good example on using the curves color correction. I should also note that this tutorial is based on using CS3.
You notice in this image the yellowish color cast and that the histogram is not touching either end of the box. It is bunched up, more on the left side, which means it is too dark. Anything on the far left is black, anything on the far right is white.
Step 1: Open your image, click the Create New Adjustment Layer at the bottom of the layers panel and select Curves. Click the show clipping check box when the dialog appears. You'll notice your image goes all white. Once you start moving the white slider (see below) the box turns black.
Click and drag the white slider (far right white triangle) and side it to the left until meaningful white appears. It could be red, yellow or black. Turn the Show Clipping checkbox on and off to see where the whites you're seeing appear in the photograph.
Once you've located a meaningful white, zoom in (if necessary) on the noticeable pixels by pressing Ctrl (Command) + (to move back out, it's Ctrl (Command) -. Press the spacebar to make the hand tool appear and then you can move your image around if necessary. Next, shift-click the sample to set your white point.
When you are finished setting the white point, click the black slider located at the left of the histogram, above the word "input". Your image will go all black (make sure you still have the show clipping box still checked). Gradually slide the black slider to the right until you find meaningful black. As above, zoom in if necessary and shift-click to set your black point.
Now that you have your black and white points set, uncheck the "show clipping" box. Your image appears. Now, take your white eye drop and click on your white point. Next, click on your black eye drop and click on your black point. Click OK to close the curves dialog box.
As you can see, the color cast is removed, and by looking at the final histogram (flattened), the histogram stretches more of the length of the histogram box and there are no large spikes to indicate blown out colors.
I hope this makes sense, but if you have questions, please let me know.
Christine
