The more advanced photographers amongst you may be familiar with the histogram function on your D-SLR, but how many of you actually use it in practice to improve the exposure of your images? If you’re not getting the most out of this photography secret weapon, then you might be interested in the below hints and tips which will help you get the most out of your histogram.
But first thing’s first, what is a histogram?
The histogram is a graphic representation of the range of tones in an image, displaying them from the darkest on the left of the graph (0 in digital terms) to the lightest on the right side (255 in digital terms).
You might think of it this way: a light meter reads the scene before you take the photo; the histogram analyses the photo you’ve just taken.
An example of the Histogram on the D3S
Image © Nikon Corporation
How can it help?
A glance at the histogram will tell you if parts of your photo are over- or underexposed. Through its analysis of your image’s tonal range, you can see if you need to adjust your exposure.
Here’s how to interpret the display:
Overexposure means lack of detail in the highlights; underexposure, loss of detail in the shadows. The histogram will instantly reveal the situation: a heavy concentration at the left side of the graph means the image is underexposed and you’ve lost detail in the shadow areas; a heavy concentration at the right means your highlights may be blown out. The remedy? You can increase your shutter speed, close down aperture or lower your ISO to correct overexposure; the opposite settings will serve to correct an underexposure.
When should it be used?
It’s not always necessary to use the histogram. In fact, selective use is best. Few, if any, photographers look at the histogram for each and every photo they take. In most cases, your camera’s meter will set the correct exposure for the scene.
But you should check the histogram when a scene’s lighting is especially tricky; when there are areas of deep shadow and bright light in the same scene; and when you’re going to take a series of images in the same setting and want to be sure your exposure is right on target.
Another histogram hint
Here’s something you might want to use in connection with the histogram: the highlight overexposure warning. Set this option (again, see your manual for the specific activation method) and areas of overexposure will blink in the playback image. When you see these flashes of light—most people call them “blinkies”—you’ll know exactly which areas of the image are overexposed.
And when you’ve mastered the basics…
Several Nikon D-SLRs feature secondary, colour histograms. As per the image at the top of this blog, when you choose to display the histogram on your camera, you’ll see three small graphs that show the intensity of the RGB (red, green and blue) colour values in the scene. If you need to adjust these values, the camera’s white balance control is the way to do it.
Some Nikon D-SLRs also allow you to magnify specific areas of the photo on playback so you can check exposure and detail rendering in very specific parts of the image. In effect, you’re directing the histogram’s area of analysis.
Practice makes perfect
The best way to see exactly how the histogram can help you take control of your photography is experimentation and experience. Just go out and take pictures in a number of situations and become familiar with what the histogram can tell you about the results.
We hope you’ve found our histogram tips helpful. If you put them into practice, do let us know how you get on – we’d love to see your best examples on our Flickr page.