Photoshop techniques

Although its generally best from a quality, and even a visualisation point of view, to get the colours right at the time of shooting, this isnt always possible. There might not be enough time, the equipment or the conditions might not allow it, or you may only see the images true potential when youve opened it on your computer screen back at home. Here, then, is a selection of techniques you can use in Photoshop and, with the exception of the Curves adjustment, in Elements. Each adjustment has pros and cons, which well explain individually.

Color Balance

Color Balance adjustments can be carried out directly on the image, or using an adjustment layer. The Color Balance dialog contains three sliders Cyan/Red, Magenta/Green and Yellow/Blue; note that these are pairs of complementary colours. In our sample shot, our subjects skin tones have a magenta tinge, so we can counteract that by moving the Magenta/Green slider to the right, which will shift the images colour balance towards green and away from magenta. You need to develop a good eye for colour casts in order to use the Colour Balance dialog effectively; to be able to fix this shot effectively we needed to ascertain that the unwanted tinge was magenta, rather than red (which is what it looks like at first glance). For a more extreme effect, we can increase the Red/Cyan to 100 and reduce the Yellow/Blue to -100; this gives the warm colours youd expect from candlelight or firelight.

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Hue/Saturation

The Hue/Saturation adjustment works in a slightly different way to Color Balance. The Hue slider shifts all the colours along the colour spectrum; this can solve some colour problems, but the effects can be unpredictable, and hard to control. At the same time, you can use the Saturation slider to increase the strength of all the colours in the image. Our original image was shot on an overcast day, and has distorted and flat-looking colours. We can try to boost the colours by increasing the Saturation level, but this also exaggerates the unwelcome red/purple cast in the brickwork beneath the ivy leaves. The solution is to adjust the colours independently. First choose the nearest colour from the Edit menu in the Hue/Saturation dialog. Then use the eyedropper to click on the part of the image you want to alter; your hue and saturation changes will be applied to this range of colours only. Our final shot features reddened brickwork, and greener leaves.

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Levels

By default, the Levels dialog displays the combined RGB values of the pixels in the image, but you can open the menu at the top to view and edit the red, green and blue colour channels independently. This affords you more flexibility than applying the Auto Contrast and Auto Levels. Auto Contrast maximises the tonal range without altering the ratios of the three colour channels, while Auto Levels optimises the channels individually, which can correct colour casts, but can also introduce colour casts where you didnt have any. Our original shot has a strong yellow cast, because we used a coloured graduated filter over the sky; simply applying Auto Levels restores a much more natural colour balance. In the final version, however, weve gone further, by opening the Levels dialog and moving the red channels midtone slider to the left to make the colours redder, before selecting the RGB channel and moving the midtone slider to the right to darken the image as a whole.

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Curves

Like many digital camera images, the shot were starting with here looks a bit flat, even though the histogram displays a full range of tones. Our first attempt at adjustment involves dragging an S-shaped curve in the Curves dialog box; this darkens the shadows slightly, and lightens the highlights but, because the curve is tighter in the centre section, it adds contrast to the midtones. Our final example is more extreme; it exaggerates the contrast in a specific tonal range, that of the red brickwork. The way to do this is to open the Curves dialog, then click and drag your cursor over a critical area of the image (it will change to an eyedropper); the tones in that area are displayed on the curve as you drag, and this is the point on the curve where the curve gradient needs to be made much steeper. Note how increasing contrast also increases saturation; the two are inextricably linked, and if you sort out your images contrast properly, youll often find out you dont need to increase its saturation.

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Brightness/Contrast

Brightness/Contrast adjustments are the easiest to understand, but theyre also the most destructive in terms of image quality. Why? Because increasing the contrast pushes dark and light pixels off the scale, so that shadow areas of your image become blocked in, and highlight areas are bleached out; if you display Photoshops Histogram palette while you work, youll see what we mean. You need to use the Brightness/Contrast dialog with care, then. The image were starting with is rather light, and lacking in contrast, so our first attempt at improving it is simply to reduce the Brightness value. This looks OK superficially, but the histogram shows that the highlights are no longer a true white, while a lot of shadow detail has been clipped. Increasing the contrast strengthens the colours (remember the link between contrast and saturation), but yet more shadow and highlight detail has been lost.

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Taking it further

The colour adjustments weve looked at have largely been aimed at correcting or enhancing colours. But many of the techniques can be adapted to produce more extreme colour alterations. Using Photoshop, its possible to mimic many of the effects once generated in darkrooms, including solarisation, sepia-toning, cross-processing and more. Indeed, with a little experimentation, its possible to come up with effects never seen before and sometimes effects youll never want to see again! In addition to the ideas we introduce here, you can try out Photoshops different layer blending modes, either by blending two images together, or by duplicating the current image layer and then changing the way it interacts with the layer below. And dont just stop with a single modification or filter try combining them. There are so many permutations in Photoshop that you may never discover them all.

BEFORE-How many different ways are there of changing the colours in Photoshop? Heres the image were starting with

his old-fashioned sepia treatment was created in moments using the Hue/Saturation dialog, with the Colorize box checked and Hue value of 30 entered

These rather surreal colours were also created using the Hue/Saturation dialog, but this time we simply moved the Hue slider until we achieved a pleasing image.

This pseudo-solarisation effect was created using the Curves dialog, by pushing the centre of the curve upwards, then dragging the end point back down to zero.

This effect was created using Photoshops Gradient Map adjustment. It maps the gradient you choose to the tones in the image, based on their brightness values.

This subtle colour wash effect was achieved by converting the image to Lab mode,then applying a 50-pixel blur to the two colour channels