Advanced image editing

Most digital cameras come with some kind of image-editing software, but while these programs might be alright for basic quick-fix repairs, they can only go so far.

One problem is that they don’t do much beyond automatically adjusting contrast and colour, with maybe a little red-eye correction. The other is that they don’t really show you what they’re doing to your images.

The fact is that automated ‘quick fixes’ can do more harm than good. They can exaggerate contrast so that large areas of dense black shadow appear, or they can ‘blow out’ brighter areas to a featureless white. They may distort colours and often oversharpen detail.

With the kind of information and feedback provided by a proper image-editing program, it’s possible to make a better job of routine image enhancements. This needn’t cost a lot, either. Our examples and explanations are based around Photoshop Elements. Version 5 has just come out, priced around £70.

What’s good about Elements is that it uses tools and techniques that have become pretty much standard, so that you can usually duplicate them in other programs without much difficulty. We’re going to use some of these tools to fix photo problems in four key areas that between them account for most photo woes: exposure, colour, distortion and sharpness.

Exposure issues
In the past, the most common problem with snaps was exposure. Today’s digital cameras have far more sophisticated exposure systems so this happens less, but light-toned subjects like snow, white clothing or white buildings can still make the camera underexpose and produce shots that are too dark.

Some cameras have a tendency towards overexposure. They make sure that shaded areas in the shot are reproduced well, but this can mean that lighter tones in the background are washed out.

It’s often possible to fix these exposure problems in an image editor, although it may be that in some cases the camera simply hasn’t recorded any image data for you to recover. This can happen in especially dark or light areas of the picture.

This is where you need to see the image histogram. This is a chart that shows how the tones in your photo are distributed along a brightness scale running along the bottom from left (the dark areas) to right (the light areas). The Levels tool in Elements displays this histogram and also provides the tools needed to fix any exposure problems it throws up. To do this, go to the Enhance menu, and select Adjust Lighting, and then Levels.

If the histogram tails off before the left-hand or right-hand end of the scale, it means the image doesn’t have full black or full white tones, respectively. Moving the black point and white point sliders underneath to line them up with the ends of the histogram will maximise the tonal range of the photo and can solve many exposure problems.

However, if the histogram is clipped at either end of the scale, there’s not much you can do. This means shadow or highlight detail has been lost for good, and there’s nothing to be gained from trying to get it back.

There is one more control in the Levels tool that can be useful. Dragging the mid-point slider left or right will lighten or darken the image without clipping any of the shadow or highlight detail.

The shot we used as our exposure example had to be improved by a slight Levels adjustment, but the tower remained too dark compared with the sky. The solution to problems like this is to use the lasso tool to select the shadowed area, then choose Select and the Feather command to soften the edges of the selection so that you don’t see where the repaired section joins the rest of the image. A new Levels adjustment will now apply only to this shadowed area, which can be lightened independently of the rest of the image.

To summarise, the Levels tool can not only show you what’s wrong with the photo and whether it can be fixed or not, but also provides you with the tools to do it. And if you make a selection first, you can adjust parts of the image without affecting the rest.

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