Local Contrast Enhancement and Curves adjustments are both post processing techniques that can be used to enhance a photo quickly and easily. Both techniques can be applied in both Photoshop Elements as well as the full Photoshop CS versions. Most other image editing programs such as Paint Shop Pro also have similar tools available to achieve the same effects.
The Keyboard shortcuts mentioned in this article are based on the Windows version of Photoshop. If you using a Mac, where a keyboard shortcut uses the Ctrl key, use the Cmd key instead.
Local Contrast Enhancement
Local Contrast Enhancement (LCE) works by darkening or brightening areas where a transition between a dark and light tone occurs. It is a good way to add contrast to an image without darkening larger dark areas or brightening larger light areas too much.
To apply LCE to an image, start by duplicating the current image – there are a few different ways you can do this:
- Select the current image layer and press Ctrl + J, or
- Click the layer and drag it down to the ‘New layer’ icon, or
- Press Ctrl + A to select all. Press Ctrl + Shift + C to copy merged. Now press Ctrl + V to paste, you may need to adjust the positioning of the pasted image slightly using the move tool to ensure it is exactly aligned with the original image (or you can use Ctrl + Shift + V to paste in the same position if you are using Photoshop CS5). Use this option if you want to apply the effect to a document made from multiple layers.
Now with your new layer selected, on the menu go to Filter > Other > High Pass. Choose a radius of 100 pixels for the High pass filter, then click OK.
Change the blending mode for the Highpass layer to Overlay, and reduce the effect by lowering the layer’s opacity. Typically an opacity of 15-30 percent works well, though you can of course use a higher opacity for a stronger effect.
A curves adjustment is an easy way to change specific tones in an image. Although it can be used to darken or brighten a whole image, usually we will use it to increase the contrast by darkening the dark tones, and brightening the light tones.
Photoshop Elements doesn’t include a real curves adjustment ability, so doing a curves adjustment isn’t as easy as it is in Photoshop CS. Still, it is possible to perform curves adjustments in Photoshop Elements, you will need to start by downloading and installing the Smart Curve Curves Adjustment for Photoshop Elements.
Although Photoshop Elements does include a rudimentary curves adjustment that can be accessed via Enhance > Adjust Color > Adjust Color Curves, I would recommend installing the curves plugin for the greater control that it gives you.
The Smart Curve doesn’t work as an adjustment layer, so you will first need to make a copy your image to apply the adjustment to (see the section above for how to create a copy layer). For this image I used the copy merged method as I have more than 1 layer making up the image.
With the copied layer selected, go to Filter > easy.Filter > SmartCurve. The SmartCurve window opens, and on the left you can see a box with a diagonal line going from the bottom left to top right. This represents the tones in the image, from black in the bottom left corner, to white in the top right corner.
For my image, I want to keep the bright tones roughly the same, so I click on the curve around one third in from the left edge. I want to darken the dark tones, so I click on the curve around one third in from the left edge, and then drag this point down a bit.
You can add as many points to the curve as you want, and move each point up or down, usually though you will only want to add one or two points.
In Photoshop CS, to access curves you click the adjustment layer icon, and then choose ‘Curves’. In the adjustment panel you can then adjust the curve.
Local Contrast Enhancement and Curves adjustments are very useful basic Photoshop techniques to know for enhancing digital photos. Remember that with both techniques you can adjust the opacity of the layer to change how strong the effect is. Sometimes you’ll want to use both techniques together, sometimes you might just want to use one of the techniques.
The benefit of these simple Photoshop techniques is that they’re quick and easy to apply, so you can apply the effect, then undo it if it doesn’t suit the image. Local Contrast Enhancement is particularly suited to images with a lot of low contrast texture you want to bring out. Curves adjustments are more useful for globally increasing contrast, for example for a photo shot through a dirty window.
Source by Dave Kennard