Improving Contrast and Brightness

Note that the demonstration pictures here are included as small versions - if you click on the picture, a larger version can be seen.

You should see a nice screen grab nearby of the Tone Balance control. This control is called by many names in different programs, including just "balance", "tone", or "levels". In Picture Publisher 8, this can be accessed by selecting the Tone Balance item from the Map menu. Find something similar in your program now. If your program doesn't have a similar control, try the Using Percentages section below instead.

Right - let's take a quick tour of the main features of this window. First, at the top of window is the "Channel" option. This lets you choose whether you are going to alter the Red, Green or Blue channels, or the Master channel. As we are trying to alter the picture contrast, we need to use the Master channel.

The next major feature is the big graph in the middle of the window. This graph is a histogram - it shows the frequency of different intensities, or brightnesses in the picture. You can see a left-to-right black-to-white gradient above the graph, which shows the colour the graph corresponds to. As we can see, the peaks in the graph (most common intensities) are all towards the white end of the scale - so the picture is very bright.

Sitting under the graph are three pointy things. (Ignore the blue bar for now.) These are labelled (barely) with S, M, and H - Shadows, Midtones, and Highlights. Moving the controls changes the spread of light and dark in the picture. For instance, moving the shadow control rescales the distribution of lightness to make the darkest colour in the picture the one at the position of the marker. If this sounds complicated, just try it - it is easier to understand when you see it in action. You can always click "cancel" or "reset" if you don't like the effect. Notice there are number boxes where you can type in values if you prefer.

Now - how can we increase the contrast in the picture? Because the picture is very light (as the graph shows), we need to adjust the spread of lightness so that the picture's shadows are made into something nearer to black. Grab the shadow marker, and move it until it reaches the start of the raised section of the graph - about to where the blue bar marker is (I added that - does it show?). You will need to fiddle with it a bit to get it looking best, but you should find the picture suddenly gains a lot of contrast, with deeper, nicer shadows.

I've included here my efforts, next to the original. (Don't forget to click for an enlargement.) This took about five seconds, including the time taken to open the window. Not bad.

On the left of this picture, we have a version where I have moved the shadow slider too far to the right. It sacrifices way too much shadow detail. See how dark and miserable Bob looks? Conversely, the picture on the right has the highlights control adjusted too far to the left, causing "white out", as if Bob just exploded. Both of these scenarios should be avoided.

By adjusting the midtone slider, you can leave the perfect shadows/highlights untouched, and instead just increase contrast in the parts that need it. This can be especially good if you working on a picture with lots of awkward skin tones. A useful tip here is that moving the midtone slider to the right (towards highlights) actually darkens the picture, and moving towards shadows lightens the picture.

This picture is from PP8. Your program may use just sliders or percentage boxes, but the idea is the same. Again, note the option at the top, allowing you to choose the tonal range - Full, Shadow, Midtone or Highlight, like the Tone Balance control. This really is ridiculously easy to use. Simply increase the contrast control to boost contrast, or the brightness control to increase brightness. And that's it.

You may be wondering why we bothered with the Tone Balance control at all. There are two reasons - the first is, Tone Balance give us the nice histogram. Learning to understand the histogram can make your work easier later. The second reason is that Tone Balance, in my opinion, actually makes it far easier to adjust to the correct contrast and brightness, because you can see the peaks on the graph that mark out features. It also gives nicer results I think.

However, for a quick play, the percentages method might be more up your street, especially if the tone balance control seems confusing, as it can be. But, because I started on percentages too, here are my two hot tips:

• To improve contrast, it often pays to increase the contrast control but decrease the brightness control at the same time. This allows you to increase the contrast further before the picture "whites out". Similarly, to increase picture brightness, increase the brightness control but decrease the contrast control, to prevent "black out".
• Good values to try to increase contrast are Contrast+20%, Brightness-10%. These give reasonable results on most only-slightly-out pictures, and make a good starting point for the rest.