As far as digital technology has come, there’s still one thing that digital cameras just won’t do: give you perfect colour every time. In fact, if they gave us perfect colour 50 per cent of the time, that would be incredible. But, unfortunately, every digital camera sneaks some kind of colour cast into your images. Here’s how to get your colour in line.

Set preferences In Adobe Photoshop CS3, open the photo you want to colour correct. Under the Image menu, select Adjustments➝Curves (or press C-M). Curves is the hands-down choice of professionals for correcting colour, because it provides a greater level of control than other tools, such as Levels, which pretty much limits you to just three adjustment sliders.

First, we need to set some preferences in the Curves dialog box so we’ll get the results we want when colour correcting. We’ll start by setting a target colour for our shadow areas. To do so, double-click on the Curves dialog box’s black Eyedropper tool. This brings up the Color Picker. In the R, G, and B (Red, Green, and Blue) fields of this dialog box, enter the number 10. Now click on OK to save these numbers as the target shadow settings. Because these values are evenly balanced (they’re all the same number), our shadow areas won’t have too much of one colour, and by using 10, we get dark shadows while still maintaining shadow detail in our prints.

Now we’ll set a preference to make our highlight areas neutral. Double-click on the white Eyedropper. The Color Picker will appear, asking you to select a Target Highlight Color. Enter 243 in the R, G, and B fields. (To move from field to field, just press the tab key.) Click on OK to set those values as your highlight target colour.

The image on the left suffers from a bluish colour cast. After a trip to the Curves dialog box, the colours are much more accurate

Now set your midtone preference. You know the drill: double-click on the midtones Eyedropper (the middle of the three Eyedroppers). Enter 133 in the R, G, and B fields. Then click on OK to set those values as your midtone target colour. That’s it – you’ve done all the hard work. The rest is pretty easy.

If you still have the Curves dialog box open, click on OK to exit it for now, and you’ll get a warning dialog box that asks whether you want to save the new target colours as defaults. Click on Yes, and from this point on, you won’t have to enter these values each time you correct a photo – they’re now the default settings.

Correct shadows Now that you’ve entered your target-colour preferences in the Curves dialog box, you’re going to use the same Eyedropper tools to do most of your colour correction work.

Let’s start by setting the shadows. Press C-M to bring the Curves dialog box back up. Look at the photo and find something that’s supposed to be black. In most photos, this won’t be a problem – you’ll see a dark area of shadows or a black car tyre, for instance. But if you can’t find something that’s supposed to be black, then you can have Photoshop show you exactly where the darkest part of the photo is.

There are two sliders directly under the curve grid that can help you. Press and hold the option key and click on the left slider (Shadow). The image area will turn solid white. As you drag the slider to the right (while still holding the option key down), the first areas that appear on screen are the darkest parts of your photo. Remember where those areas are (in our example on page 103, it’s the shadow under the first pot on the left).

Now that you know where the shadow area is, drag the Shadow slider back to the left, and release the option key. Now click on the black Eyedropper, and (while the Curves dialog box is still open) click once on that shadow area in your photo. The colour cast will be removed from the shadow areas.

Correct highlights Now, on to setting the highlight point. Find something that’s supposed to be white. Again, this is usually pretty easy, but if you can’t find something white, you can use the trick you just learned to have Photoshop show you where the lightest part of your photo is. Press and hold the option key, but this time drag the right-hand slider (Highlight) to the left. The screen will turn black, and as you drag the slider to the left, the first white areas that appear are the lightest parts of your image.

Now that you know where your highlight area is, drag the Highlight slider back all the way to the right, and release the option key. Click on the white Eyedropper, and click once on that highlight area. Try and look for a white area that has some detail (rather than clicking on a specular highlight, which is a blown-out highlight area with no detail, like the sun or a bright sun reflection on a chrome car bumper).

Correct midtones Now for your third click: finding something that’s supposed to be a neutral grey. This one’s a little trickier, because not every photo has a neutral grey area, and the Curves dialog box doesn’t have a “find the grey” trick, as it does for shadows and highlights (for a workaround, see “Finding a neutral grey”). In the example photo, the neutral grey is in the edge of the large vase on the ground. This click neutralises the colour cast in the midtones.

This article is an excerpt from The Adobe Photoshop CS3 Book for Digital Photographers by Scott Kelby.