In this blog we are looking at the various ways to check you exposure, and nail a good exposure every time. Although there are various ways of checking exposure, some are very much better than others; if you want to know which is best, then read on...
What is a perfect exposure?
A perfect exposure is normally understood to mean one where the scene is well lit. and not too dark or too bright. More specifically we normally want to achieve an image where detail is maintained in both the shadows and in the bright parts of the image such as the sky.
There are of course occasions where you might want to break this rule, such as creating an image with intentional silhouettes (areas of under exposure) but in the main, as photographers we try to achieve a 'perfect' well balanced exposure.
Below is a well exposed image, with detail still visible in both the shadow areas, and the bright areas.
Ways to check your exposure
1. Check the image on the LCD screen or viewfinder
The easiest way to check if you have a good exposure is to check what it looks like on the screen or through the viewfinder. Does it look well exposed? With some DSLR cameras you might have to take the photo first and then check what it looks like, but for many other cameras (phone cameras, compact cameras and mirrorless cameras) what you see on the screen will generally be what the final photo will look like.
Although this seems like the simplest method, it actually isn't fool-proof, since sometimes the screen brightness can be misleading; I therefore suggest that one of the other methods below is always used as a sense check.
2. Check the histogram
On most camera displays there will be an option to show a histogram of the exposure before you take a photo (with some DSLR cameras it may only show the histogram once you've taken the photo). A histogram is essentially a graph showing the brightness of all the pixels in the image, from dark / black on the left to bright / white on the right. The number of pixels of each brightness is shown by the height of the graph. Note that on many cameras you may need to press your 'Disp' button multiple times until the histogram is displayed.
For a well exposed image, the graph should show all of the image content somewhere in the middle section of the histogram, with little or no content at the far left or far right of the graph. The image below shows a typical histogram for an underexposed image (left), well exposed image (middle) and overexposed image (right).
For more info on the histogram, and how to use it to 'expose to the right' see this recent blog article.
3. Use the exposure meter
Another graphic that is available on most cameras, is a simple exposure meter which directly shows you whether your camera light meter thinks the image is under exposed, over exposed or well exposed. The image below shows the exposure meter on a Canon camera (other cameras will have something similar), with a scale from -3 to +3. When the shutter is half pressed, the camera's light meter will take a light reading and a small arrow should be displayed below this scale showing the current exposure; If it is well to the left, this is showing your photo is underexposed. If it is well to the right, your photo is very over exposed. A perfect exposure would show the arrow under the Zero mark.
Using the exposure meter is by far the best way to assess if you have the perfect exposure. On many cameras, you might have to press the 'Disp' button (somewhere on the back of the camera body) several times before the exposure meter is shown on the LCD display
How to change your exposure if necessary
If you're shooting on fully automatic mode, your camera will use it's light meter to measure the brightness of a scene, and set the camera settings to hopefully give you a 'perfect' exposure.
However, there are some occasions where cameras will struggle to do this well, such as in snowy scenes or when the sun is in the photo.
So, even when shooting on automatic your camera may get the exposure wrong wrong, so it's worth understanding how to check your exposure (see methods below). If the exposure is too bright or too dark then you can simply use exposure compensation to adjust it - for how, please see my recent beginner's guide to exposure compensation.
If you are shooting on one of your camera's manual modes and you have control of one or more of the Aperture, Shutter speed or ISO, then you can simply change one of these settings to make the image brighter or darker as required. You can check out my beginner's guide to getting off auto here.
Once you have changed your camera settings, then you obviously need to re-check your exposure to ensure that it is now 'perfect' using one of the three techniques from above.
Want to jump-start your learning?
Don't forget that if you want some direct help with your photography, I offer a range of 1-2-1 photography courses for Devon based folks. If you're not nearby then I also offer residential weekends for beginners or intermediate photographers.
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