I am so excited to announce a new series about photography called, “Ten Things All Photo Geeks Must Know.” It is for the more serious amateur photographer who shoots with a digital camera. These ten tips are the basis for a solid foundation in photography. Once you have these skills in your proverbial camera bag you will be able to advance quickly. Some of the posts will apply to film cameras as well but I am writing this series with an aspiring digital photo geek in mind.
Tip One- What is a Histogram?
A histogram is a bar graph that was originally created for statistical analysis. But photographers have adopted it to provide a graphic representation of a digitally recorded image. When I am shooting I nearly always have my camera set so that I can see my histogram as I go along. More so than the image itself, it is my guide.
When you capture a photograph your digital camera locates each picture element, or pixel, on this horizontal scale according to its brightness from 0 (black) to 255 (white). Pixels of equal brightness are stacked vertically to create lines of varying heights. The end result is a graph that appears as a smooth curve, a series of jagged lines, or a combination of both. If your histogram is too close to 0, or absolute black, there won’t be any image at all or it will be too dark. If it is too close to 255, or absolute white, there will be nothing there except oversaturated pixels with no image information.
There is no IDEAL histogram. It is just a guide. It is a great tool to see if the brightness range of the scene you are photographing will fit within the dynamic range of your camera. Let me show you some examples of how to use your histogram.
Here we have a photo of a newborn named Henry. The values represented in this histogram are fairly evenly placed between 0 and 255, or from black to white. You can see the greatest number of pixels are stacked at about 175, closer to white. This would represent the yellow quilt, which takes up most of the image. There is also another hump around 100, or closer to black. That would be Henry’s brown onesie. If the pixels in this histogram hit the white wall that would mean that Henry’s handsome, white face would be overexposed. We can’t have that as there would be not detail whatsoever! If the histogram hit the black wall that would mean that any shadows or darker parts of the image, such as his clothing and brown eyes, would not have any detail. In general I like to see my histograms look like this, with pixels starting at about 10, running to about 240, without hitting either wall.
As soon as I give you a rule I will then immediately break it, as rules are made to broken! There are times when you do want to “hit the wall”, either black or white. In this case I wanted to lose the detail in the window. The scene outside was not important but rather distracting. I thought this heavenly window set the right mood, so I overexposed it. I was very careful, however, to properly expose faces of this beautiful family.
On the other side of the spectrum, sometimes you purposely hit the black wall. Here we have the same darling boy, at 3-months-old. I wanted the black background to not have any detail. It is not an important but merely serves to highlight the subjects by contrast. And again I was very sure not to hit the white wall as I would lose all detail in the skin tones.
That concludes the first installment of this series. Please be sure to ask any questions you may have! I am also always open to suggestions for photo stories. You may write me at firstname.lastname@example.org. Thanks for reading!