Sometimes you'll take a shot and when you get home realise it needs a little more punch. In the above shot, for example, the shadows are a little flat and the whole shot just looks a little dull.
To improve it, we are going to make some basic changes with the Levels feature to adjust the overall tone of the shot. We are using Photoshop but any editing program that features a Levels option can be used.
Most editing software programs offer auto functions which change levels and other settings automatically at the click of a button. Here we used Photoshop's auto tone option as an example (Image>Auto Tone).
Even though it's done an OK job it isn't perfect. To make a more precise adjustment, you need to find the Levels option. You can do this by going to Image>Adjustment>Levels but the best way is to actual create a Levels adjustment layer (which will show you how to do in a second) as this means you can edit your image none-destructively and you can make further tweaks to the adjustment if you're not happy with it once you've clicked OK.
To create an adjustment layer click on the black and white circle at the bottom of the layers palette and select the adjustment you want to make which in this case is Levels. When you do, a new dialogue box will open that has a graph of the image's tonal range in it which looks a little like a mountain.
The peaks show the detail in the picture represented as greyscale. Detail to the left is the shadow areas and to the right highlights with the midtones in between. There are three sliders underneath: Black for shadow, grey for midtones and white for highlights. Each one of these can be dragged either way to change the brightest or darkest point of the photo.
If you drag the white highlight triangle to the left it will lighten the picture. We've exaggerated the effect in our example, taking it too far so you can easily see the difference it makes. Notice how all the detail has now disappeared in the building's wall. If you drag the black, shadow triangle to the right it will darken the picture. Again, we've exaggerated the effect here by taking it too far to the right. Notice how all the detail has now disappeared in the shadow areas.
Here are the settings we changed for our image but do remember this will differ from shot to shot.
Notice how we've moved the white triangle over towards the beginning of the graph but not right to the beginning. If we did it would mean the lightest pixels in the photo would be white, creating a similar effect to what Photoshop's auto setting did earlier. By leaving the slider just off the edge of the graph it ensures that the highlights in the picture are less bright and more accurate to this scene.
You can see the before and after shots here: