I think my photos have a good exposure but why don’t my histogram graphs look like the normal ‘mountain shape’ that I’ve seen online?
BRIAN SAYS… A histogram is a graphical representation of the distribution of light levels in a scene with the left being full black and the right full white. Initially for a typical scene you should try to ensure that your histogram doesn’t have all the peaks at the extreme left or right side. Histograms on the camera are derived from the JPG and as such you have a little more dynamic range to make use of if you shoot in Raw. Also the Picture Style set on the camera will impact the histogram, Neutral has the widest range on the histogram, but on-camera images will look flat.
An underexposed photo with the histogram right up to the left side will be really dark and if you attempt to boost the image in software afterwards, detail is limited and ugly noise becomes more visible. An overexposed picture with the histogram bunched up on the right side is also problematic since the details will be wiped out, even if you try to bring them back in the edit.
The way the tones are spread over the histogram depends on the content of the image. A polar bear on ice would have most peaks on the right of the histogram, and conversely a dark subject at night would have the majority on the left of the histogram. With live view and mirrorless cameras, a histogram can be overlaid on the image before capture so you can adjust the shutter speed, aperture and ISO settings to achieve a good exposure before shooting.
Using Levels or the Curve tools in software to increase the range of tones in an image can pull individual tones away from others nearby, resulting in a comb-like histogram with gaps between the peaks – a clear sign that an image has been overprocessed and will be problematic to print.