Discussion

Levels Command vs Adjustment Layer

We can achieve exactly the same effect using a Levels adjustment (Image > Adjustments > Levels). However, using this command applies the adjustment directly onto the image layer, which could cause some problems if you want to alter or remove the adjustment in the future.

In this solution, we used an adjustment layer to modify the levels non-destructively. If you look in the Layers palette, you'll notice Levels adjustment layer in the Layers palette

that a special layer has been added. This layer contains the levels adjustment, and affects all the layers beneath it. The original photo layer remains untouched, so if you decide that you don't want the adjustment after all, you can hide the adjustment layer using its eye icon. You can easily alter the adjustment by double-clicking on the adjustment layer's thumbnail (this will bring up the Levels dialog box).

While this method is recommended because it keeps the original image intact, as I mentioned earlier, the adjustment layer affects all the layers beneath it. Using an adjustment layer in a document that has multiple image layers can get a bit tricky, particularly if you want the adjustment layer to affect a specific image layer alone. In situations like this, consider adding a layer mask to the adjustment layer (to specify the area of adjustment), or applying the Levels adjustment to the image layer itself.

About Using Levels

The Levels dialog box displays a histogram, which is a graph showing the number of pixels present at each intensity level. The empty space on the right-hand side of the graph for our winter photograph, displayed

Sample histogra^n at right, shows that there are hardly any pixels in the higher highlights range. In other words, there are no (or very few) white pixels in the original image.

When you adjust the three sliders underneath the histogram, Photoshop "remaps" the tonal values of the image. In the winter photograph solution, we dragged the white slider to the left and placed it directly beneath the end of the graph. Our image brightened because Photoshop identified the pixels on the graph that were originally gray and remapped them to the whiter end of the spectrum. The rest of the image was adjusted to accommodate the change. Dragging the gray slider (which represents the "middle" tones) towards the left also increased the brightness of the image, because Photoshop remapped the darker tones to midtones.

If you're using an adjustment layer, the shape of the histogram itself won't change. However, when you apply the Levels command, the histogram is altered to reflect the remapped

Histogram after applying the Levels adjustment

tonal values, changing the state of the image permanently (unless you undo the command). As you can see in the example on the previous page, the tonal values now stretch across the entire spectrum (there's no space on the right-hand side of the histogram).

Making Blacks Blacker

Now that you know how the histogram and its sliders work, it should be easy for you to make the blacks in the image blacker. Simply drag the black slider towards the right. This will give your image a little more contrast, making it appear cleaner and less muddy.

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