AnandTech Guide to Better Photos: Post-Processing

Levels

Almost every photo can benefit from a levels adjustment. We are going to show you some examples that demonstrate how a levels adjustment can bring life back into your photos. This is particularly effective for images that are too dark. The levels command in Photoshop and Elements allows you to remap the brightness levels in a photo resulting in a high contrast image.

Original image
Click to enlarge.

When we decided to photograph the image above, the leaf attracted our attention because of its bright red color contrasting against the hood of a light blue Chevrolet Caprice. Unfortunately, the image right out of the camera doesn’t look like how we remembered it. With two simple levels adjustments, we can fix this problem. Once you are familiar with this process, it should take you less than 30 seconds to perform.

1) Open the Levels dialog by pressing Ctrl-M (Mac: Command-M). Again, you could just as easily use a Levels Adjustment Layer if you think that you might want to alter it later. The first thing that you will see is a histogram. A histogram displays the brightness of an image starting with the darkest information on the left to the brightest information on the right.

By looking at the above histogram of our leaf, we can see that most of the light information is in the midtones. There is a considerable amount of shadow detail (left), but there is virtually no highlight detail (right). What we want to do is “stretch” the light information over the whole histogram. In other words, we want to remap the brightness values so that our histogram looks more balanced with shadow, midtones, and highlight detail. As you will see, this is actually very easy to do.

2) Click on the black slider on the left directly under the histogram (circled in red below). Slowly drag the slider to the right.

To see exactly what you are doing, make sure that you have the “Preview” box checked and hold down the “Alt” (Mac: Option) key. With the Alt key held down, you can see exactly when a color channel begins to clip. Drag the slider to the right until just before you see the clipping.

Dragging the black slider to the right while holding “Alt”
Click to enlarge.

In the screen capture above, you can see that we stopped just as we started to clip some of the color.

Now, use the same technique to drag the white slider to the left and stop just before clipping any color channels. You should already see a tremendous difference if your photo is anything like ours.

Dragging the white slider to the left while holding “Alt”
Click to enlarge.

Again, with the white slider, we stopped just before any serious color clipping occurred.

Here are the results that we achieved by simply adjusting the black and white sliders:

Original image	Image after levels adjustment
Click on above images to enlarge.
Original histogram	Histogram after levels adjustment

You can clearly see how we’ve “stretched” the histogram to cover more of the brightness range. This has increased the contrast and given the photo more “pop”. Below is a final comparison where we pulled the white slider just a bit further to the left. Although this causes some slight color clipping, it is hardly noticeable and the effect is just what we wanted.

Hold mouse over image.

Below is another example of how this simple levels procedure can bring detail and life back into boring images.

Hold mouse over image.