Setting black and white point and color balance your image

You can use the curves dialog to set the black- and white point of your image and to do some effective colour correction. In the right bottom of the curves dialog you'll find three color pickers. Select the left one and click on an area of your image that you know is supposed to be all black, that sets the black point. Now select the right picker and click on an area of your image that's supposed to be all white. and this sets the white point of your image. If you have a neutral grey colour in your image, use the middle picker to select that. This will set the white balance for your picture and help you achieve more natural colours. Try to click on several grey areas in the image in succession because their slight difference in tone might give you different white balance results.

Use Curves to manage your picture's tonality

Here's how the curve tool works: the horizontal axis represents the range of original brightness values of your image, and the vertical axis is the dynamic output range. And the actual curve is the function that is applied to the incoming values in order to create the result. What that means will become quite clear when we look at the following two examples.

Example 1

Let's look at an image that is generally ok, but too dark in the mid tone range. now brightening up the mid tones of this image is quite easy by just dragging the middle area of the curve slightly up.

This will leave the very dark and very bright areas of the image virtually intact and only raise the midtones. but the way it does it is in a smooth curve, so that you don't get any posterization of your image.

Example 2

The second example is an image that is pretty dull and lacks in contrast. a look at the histogram by selecting window / historgram from the Photoshop menu, reveals that the brightness distribution on this image is fairly okay and basically reaches to both ends of the histogram, so this would be a perfect application for what's called an S-curve.

What an s-curve does it that it darkens the lower mid tones of an image and it brightens the upper mid tones, both without affecting the blacks and the highlights.

One of the frequent mistakes in the beginning is to overdo the curves treatment, .. this can easily result in posterization or even a solarization effect on the image.

The curves tool has been called the scalpel among the tools that work on the images' dynamic range, and it needs a bit of practise, but then it's not as hard to use as it looks.. give it a try, and don't forget to do your changes on an adjustment layer, this way you can always go back and start over again in case you don't get it right in the first place.

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