Exposure Adjustment in Photoshop CS2
With Brightness/Contrast, Levels, Curves, and Shadow/Highlight, there's no shortage of ways to make an image brighter or darker in Photoshop. If you are in the process of migrating to the new CS2 release, you may have noticed that there's now one more way. The Image >> Adjustments menu now sports a new "Exposure" option that may well become your first choice for significant shifts in exposure.
If you shoot with a digital camera and are used to processing raw files with Adobe Camera Raw, you will find yourself right at home with the new Exposure adjustment dialog. Apart from a somewhat bizarre change in terminology, it functions exactly the same way. Adjustments are made in a linear (gamma 1.0) color space so as to retain the most detail possible throughout the tonal spectrum.
The Exposure Adjustment dialog has three controls: Exposure, Offset, and Gamma. The appropriately named Exposure slider will be the main one you are likely to use and works as you would expect it to. Calibrated in stops, it increases brightness throughout the image but affects the shadow areas far less than the highlights. Increase the Exposure sufficiently though and the image will turn solid white. Set it low enough and you will end up with solid black.
The oddly named Offset slider seems to primarily do the opposite, stretching the tonal range downward to darken the shadows without overly influencing the highlights. After adjusting the Exposure, Offset can be used to tweak the shadow and quarter-tone areas of the image while only moderately affecting the rest of the image.
The Gamma slider works in a similar fashion to the Brightness slider in Adobe Camera Raw. Moving it to the right increases the mid-tone brightness of the image, while sliding it to the left will darken the overall appearance of the image.
There are also eyedroppers for white, black and gray point setting. The Black eyedropper is linked with the Offset slider and will set whatever pixel you click it on to pure black. The White eyedropper works with the Exposure control and will turn the pixel you click it on to pure white. The Gray eyedropper also affects the Exposure and will render what you click it on to be medium-toned. Gamma is unchanged by any of the eyedroppers. You will probably find it easier to adjust an image by using the sliders than by using the eyedroppers.
Unlike in Adobe Camera Raw, holding down the Alt/Option key as you move these sliders won't show you where you are clipping any of the channels. You'll have to rely on the Histogram for check for that. Be careful not to burn out your highlights as this seems to be a significant problem when adjusting exposure on some images. It would also be nice if you could do Exposure adjustments on an Adjustment Layer, but alas, not in CS2 at least. Adobe has to save something for CS3 I suppose.
The new Exposure control works on 8-bit and 16-bit images, but was introduced to work with the HDR (High Dynamic Range) 32-bit format, also new to Photoshop CS2. We'll take a look at that, next week.