Fixing Backlighting
A common problem for all photographers is a poorly lit subject in a bright scene. If you can use your flash when you take the photograph that's the best solution; but even if you're stuck with an image that is already captured you can use your photo editor to help out.
In the case of Photoshop, a Curves Adjustment layer is the most powerful and flexible tool you can use to deal with the problem. Photoshop Elements doesn't have Curves Adjustments, but you can use a Levels Adjustment layer to do almost the same thing.
Fighting Uneven Lighting
Your camera can't capture the same range of light to dark that your eye can see. So if you have a partially lit scene, like the accompanying one of Half Dome reflected in the Merced River in Yosemite National Park, you simply can't make the entire image look good in a single image capture. The trick is to capture two images—use a tripod—one with the settings adjusted so the mountain looks good, and the other with the settings optimized for the river. It is then a simple matter to open both images in Photoshop and drag the Layer icon from one to the other (holding down the Shift key so that they are correctly aligned), thus creating a document with two layers. You can then either Erase the portions of the top layer you don't want or create a mask for it (see the next section) that you can Paint and Erase until you get the blend of the two images that's what you want.
Using Multiply to Add Detail
Many images contain areas that look washed out or lack detail. You can labor over custom curves to fix the problem, but often there is a much quicker way: using a duplicate layer and the Multiply Blend mode. Have a look at the image (above) of a lion cub looking up at us, which I took during a recent photo safari to Botswana. The facial expression is priceless, but because of the low light levels there is little contrast in the image and it appears somewhat washed out. Fortunately it's an easy problem to fix using a Multiply layer.
Photo Editing Quick Tips
Use layers
Whenever possible, don't make your adjustments directly on your image. Make a copy of the image on a new layer and adjust the copy instead. That way you always have your original safely stored. And then you can use a layer mask so that you don't even need an entire extra layer to control the effect of your changes.
Selective sharpening
Sharpen your subject, especially the hands and eyes of a person or animal, to help draw it out from the background. You can go even further by deliberately blurring the background for additional effect.
Hue/Saturation layer
Hue/Saturation adjustment is a quick and simple way to add a little bit of "pop" to the colors in an image. It's easy to overuse, so be careful, but adding a Hue/Saturation Adjustment layer and moving the Saturation slider a little to the right can often bring life to washed-out images. Another related pro photographers' trick: Try increasing the saturation of the subject only. The viewer will be drawn to the vivid subject and it will appear to stand out even more from the relatively dull background. Remember to use a Layer mask.
Advanced tip: Reuse masks
You can use the same Adjustment layer mask for multiple tweaks in Photoshop Elements, which lacks the masking commands that the full version of Photoshop has to do this directly. Just duplicate your Adjustment layer (using the pop-up menu on your layer) instead of creating a new Adjustment layer, and then use the Layer | Layer Content Options command on your new layer to change it to the effect you desire. Then you'll have a new layer with your desired mask.
In the case of our elephant example we'd duplicate our Levels Adjustment layer (either by choosing the layer, right-clicking, and selecting Duplicate Layer from the context menu, or by dragging it to the new layer icon) and then using the Layer | Layer Content Options command to change our new layer to a Hue/Saturation layer. Then all we need to do is drag the Saturation slider a little bit to the right and we're done!
Source : here