Apr
13

Perfect your histogram

Tutorials
by
Rebecca Greig

Shoot and edit with the histogram in mind and achieve well-exposed scenes every time

Low light heathland landscape taken at dawn. There are ferns in the in the foreground which gradually get out of focus towards the mid ground. There's also a tree in the horizon, providing a good focal point. Taken as part of a tutorial on Low-light landscapes.

The histogram is an incredibly useful tool for checking the exposure of your image, but it’s often overlooked for fear of it being too technical to understand. At its basic, it maps the distribution of tones in an image, and the peaks in the graph illustrate whether your photo is predominantly shadows, highlights or mid-tones. After you take a picture it’s typical to review it on the back of your camera, but as the brightness of LCD screens greatly varies, it can be hard to see if areas of your shot are slightly under or overexposed.

The best method for exposing accurately is to check your histogram, as it clearly shows whether you need to darken or lighten the next image you take. In this tutorial we’ll show you how to do so, both in-camera, and afterwards in post-processing, so that your shots capture the full range of tonal detail.
There’s no such thing as correct exposure, because ultimately it’s a creative choice, and there are certain shooting styles, such as high key, where a skewed tonal range is desirable. For genres like landscapes however, where an even balance of tones and luminance is required, the histogram should ideally appear as a bell-shaped curve. Understanding your histogram is a great way to make sure you’re recording a scene correctly, and using it needn’t add extra time to your workflow.

1  Choose graph type Most DSLRs offer to display either a brightness or a colour (RGB) histogram, selectable from the Playback Menu. It’s best to start with Brightness, as this will provide you with one easy-to-interpret graph.

Step 2 (new)

2   Take a test shot Turn on Live View, and set it to Exposure Simulation. On many cameras you can press Info to bring up the on-screen histogram as you shoot. Take a test shot so you can evaluate the exposure.

Step 3

3  Review and adjust exposure Check the histogram. If it’s too dark the graph will be skewed to the left, and if it’s overexposed it’ll go to the right. Apply exposure compensation accordingly, or adjust the settings manually.

Step 4 (new)

4  Retake the shot Shoot the scene again and review the histogram. If a certain portion touches either edge, it indicates a loss of detail. Ensure that it’s central, and there’s a good distribution of tones across the range.

Step 5 (new)

5  Tweak levels Open your final image in Photoshop, then go to Window>Histogram or click the Histogram tab. Set the channel to Luminosity, to display a histogram representing the luminance or intensity values.

Step 6 (new)

6  Finishing touches Refer to the histogram when changing the exposure of your image. Go to Image>Adjustments>Curves, and tick the Histogram option. Add nodes to the line, and drag it until your shot is correctly exposed.

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