Photographers are often advised to check your histogram, but what does a histogram show and when might it be less helpful.
What does the histogram show?
The histogram is a graph that shows the amount of the image that is composed of the tones from dark to light. Histograms show the dark on the left and the bright on the right side of the chart. The shape of the graph depends on the image, if you photograph black bears in caves then expect the histogram to be mostly over to the left of the chart, equally polar bears in the snow will have a histogram mostly concentrated on the right of the scale.
Cameras usually have a setting to display Brightness or RGB histograms. Many more recent cameras can do both in the same display when reviewing images.
What to look out for on the histogram
The histogram is a guide to exposure, and conventionally you don’t want it showing as a single line all at either end of the scale. Keeping the highlights from blowing out to white means checking that you don’t overexpose the white parts of the scene. In the picture here, the two small bright white lights on the left and toward the middle of the frame probably account for the spike at the right side of the histogram. Some people are very concerned about any spike at the edge, but I know that with a RAW I have a little more headroom to pull something back in this image.
It’s good advice to keep the dark tones from blocking up on the left of the chart, there’s less detail tonal gradation there. This means that when the exposure or shadows are lifted noise can be more visible or the image appears blocky in the shadows.
Histogram before you take the shot
Since the introduction of the EOS R you can choose to display a histogram on the LCD and or in the EVF.
I’m not a fan so my cameras actually are setup with the histogram display removed. The EVF/LCD histogram can be set for brightness or RGB. It can also be small or large in size.
Histograms change with a different Picture Style
Camera histograms are created from the JPG image that is created by the camera, either the one embedded in the RAW image, or the actual JPG itself. Without any change in exposure or subject or camera settings the Picture Style being used has an effect on the histogram. Picture Styles that increase contrast, Landscape, Standard and to a lesser extent Fine Detail and Portrait will have both the shadows and highlights further apart than an image captured while the camera is set to neutral or faithful Picture Style.
I converted a RAW image on the camera, applying a different picture style, first the Fine Detail style I normally use when taking photos, and then the Neutral style. I have shown the image with the Picture Style on the left and then the one with both brightness and RGB histograms on the right. Flipping between the two I see the histogram changes more noticeably in the RGB histograms, but there is an overall smoother shape to the brightness histogram than the more spiky look of the RAW version of the same image further up the page.
Note: the blue lines down the sides of the frame are due to setting Add cropping information on the camera.
Advent Calendar of Tips
This year I’m writing a quick tip each day up until the 25th of December, here’s some of the others I have already posted.