Welcome aboard photo enthusiasts. Continuing on from the article in the last issue discussing camera meter readings to set the correct exposure, I presented the graphic below …
If you’re in the camera “auto” or “P” (program) setting the camera will automatically zero (0) out the meter reading (depending at what you are pointing the camera at) to get a proper exposure. If you are in controlling creative mood you will have set your camera to “M” (manual) mode and adjust the aperture and shutter (depending on your creative objective) to “0” for the correct exposure.
In addition, I noted the camera meter reading is calibrated to 18% grey. Therefore, regardless of your setting (auto, program, manual or other) the readings may be incorrect if the overall scene is predominantly white or dark. Review the last article if needed to recall the details.
Now let me introduce another method of determining the correct exposure, something made available with the advent of digital photography and this is the Histogram. It looks something like this…
First, to find the histogram you may have to be, if you do not have an LCD live mode, in the review mode looking at a photograph you have taken. Pressing the camera display button will cycle you through two or three options for the LCD display… One will show the photo only, another may show the photo with various data, and another will show the photo with data and the Histogram.
I stated above that the Histogram may look something like the example provided. At the bottom of the graph, you will see the linear tonal range from white (right) to black (left). By this you can see this graph covers nearly a full range of tones. Not all photos have such a full range, so do not be alarmed if others follow a different pattern. And, also the height of the graph’s levels (or bars) should not be of great concern, as it shows the contrast range, which can be adjusted keeping in mind it is easier to raise the levels of contrast than to lower them.
What can be of concern is clipping. This is shown by the dark lines at the far right and(/or) far left of the graph below…
Clipping on the right means the whites and clipping on the left means the blacks have lost all detail, which is non-recoverable by means of software. Take, for example, clouds to our vision are white, yet nevertheless we see them with subtle yet extensive detail. If we overexpose clouds in taking a photo, they may be clipped, meaning they will have no detail and be pure blank, flat white.
The same can happen when exposing something dark… black, if clipped it will be flat black without subtle tonal details. When we see this clipping by viewing the histogram we may want to adjust the exposure. Normally the clipping will either occur on the bright or the shadow (right or left) side, so we can adjust our exposure one way or another to compensate to regain tonal details.
I’ve been using “may” frequently writing this. It can be the clipping is of no importance to you. I often photograph portraits of people using a black background. The graph would look something like this….
In this case, all I care about is the subject, and I could care less about the black background. Actually, I would prefer it to show no details whatsoever, therefore when camera histogram shows clipping on the right for this scenario, I will not be adjusting my exposure to compensate.
Notice there is no clipping on the right, only on the left.
In summation, the histogram is another method that you can affectively learn to use to analyze your exposures for optimum results. In some cameras histograms come in color, showing the red-blue-green patterns of the photo taken (or in live view, being taken). Where all three overlap you will see white, and where just two overlap you will see your secondary colors of cyan (no red), magenta (no green), or yellow (no blue). It’s essentially the same as the black and white version, accept for the color details.
While you are having fun exploring your new found exposure meter…your camera histogram I will take permission to come ashore.
James Schot has been a professional photographer for more than 35 years and has a studio/gallery in Ft. Lauderdale. Send questions to firstname.lastname@example.org.