Advanced Settings

Histogram part two

Written by Gail Bjork

Sample photographs and their associated histograms, showing too bright, too dark and balanced exposures.

Histogram: Part 1Part 3

Too Dark

toodark

Shutter Speed 1/180 sec., Aperture F2.8, ISO 50

Aim your camera out the window toward a street light at night or at a scene mostly in deep shadows, like the one above.

Look at the histogram produced:

toodark_histogram1At a glance, we can see that most of the pixels tend toward the dark (D) side. The pixels also touch the left edge, so we know that there are underexposed (“too dark” — thank you, Goldilocks) areas in our picture.

To obtain a correct exposure, we can do a couple of things, taking the above picture as example:

  • In Program AE mode, dial in a positive exposure compensation in +1/3EV steps. (For the above picture, we’ll dial in +1/3EV.)
  • In Manual mode, dial in a slower shutter speed, while retaining the same aperture. (For the above picture, the shutter speed used was 1/180 sec., so we’ll dial in a slower shutter speed at 1/125 sec.)
  • In Manual mode, dial in a wider aperture, while retaining the same shutter speed. (For the above picture, an aperture of F2.8 was used, so we’ll set a wider aperture of F2.0.)

Depending on your camera, you may or may not be able to do one or more of the above. For example, most consumer digital cameras have a maximum aperture of F2.8, so we would not be able to try the third option.

What we are doing is telling the camera to ignore its light meter and allow the light to register on the image sensor for a while longer. We want the histogram to shift right. Check the new histogram produced and adjust again if the histogram indicates the picture is still too dark.

Too Bright

toobright

Shutter Speed 1/56 sec. Aperture F3.2, +1EV, ISO 200

On a bright sunny day, aim your camera at a landscape photo making sure to include much of the bright sky or areas bathed in bright lights or sunlight, as in the picture above.

Here, I am exaggerating with a way overexposed shot (I used +1EV to force an overexposure) to illustrate the point.

Look at the histogram produced:

toobright_histogram1At a glance, we can see that most of the pixels tend toward the highlight (H) side. The pixels also touch the right edge, so we know that there are overexposed (“too bright” — thank you again, Goldilocks) areas in our picture.

To obtain a correct exposure, we can do a couple of things, taking the above picture as example:

  • In Program AE mode, dial in a negative exposure compensation in -1/3EV steps. (For the above picture, we’ll dial in -1EV since I gave it a +1EV to force overexposure.)
  • In Manual mode, dial in a faster shutter speed, while retaining the same aperture. (For the above picture, the shutter speed was 1/56 sec., so we’ll dial in a faster shutter speed at 1/125 sec.)
  • In Manual mode, dial in a narrower aperture, while retaining the same shutter speed. (For the above picture, the aperture used was F3.2, so we’ll set a narrower aperture of F5.6.)

Depending on your camera, you may or may not be able to do one or more of the above. Since the exposure settings chosen by the camera for the above picture are well within the limits of our digital camera, we have quite a bit of leeway here to play with the exposure settings.

What we are doing is telling the camera to ignore its light meter and allow the light to register on the image sensor for a shorter time. We want the histogram to shift left. Check the new histogram produced and adjust again if the histogram indicates the picture is still too bright.

Balanced Exposure

justright

Shutter Speed 1/60 sec., Aperture F2.8, ISO 50 with Flash

This is an indoors shot using flash. Without flash, the picture would have been underexposed (i.e., “too dark” — thanks, G).

The areas reached by the flash are exposed properly, but notice that the areas too far away for the flash to reach are dark.

Look at the histogram produced:

justright_histogram1At a glance, we can tell that the picture has neither too dark nor too bright pixels (i.e. it is “just right” — Thanks again, G.) with most of the pixels in the middle of the graph. There are a few pixels touching the dark edge, just as we expected.

You might want to try dialing in a positive exposure compensation in this case to see if the histogram improves. For the above picture, we’ll dial in +1/3EV and see if this shifts the histogram to the right slightly. Just be careful not to overexpose it!

This article was contributed by Yin Wong.

About the author

Gail Bjork

Gail Bjork, who is passionate about digital photography, is the owner and editor of Digicamhelp.Gail is the author of three illustrated ebooks about digital photography. A number of her photos and digital photography related articles appear at other websites.In 2006, a series of her photos, People in the Louvre, were exhibited at the Underground Photo Gallery
in Iisalmi Finland. Eight of her photos taken in the Florida scrub are on permanent exhibition at Parrish Medical Center in Titusville, Florida.Gail served twelve years as an elected member of The School Board of Palm Beach County, Florida, one of the largest school districts in the U.S. She has also been the editor of a small town newspaper and a free-lance writer. Gail and her husband owned and ran several small businesses.

1 Comment

  • I love the way this was explained about histogram.  It was very easy to understand.  I thought it was the best explanations compare to other website sources.