A Histogram can be very confusing to a new photographer or videographer. A lot of times people ignore them, not understanding them. fortunately, they are easy to use and can be very helpful.
What is a histogram?
A histogram is a chart of how exposed the pixels in your image are. The x-axis represents black to white, with grays between. These are laid out 0 to 255 totaling 256 shades. The y-axis represents how many of the pixels in your image are that value. You can see a picture’s histogram on your camera and it will tell if you need to adjust the exposure and shoot again. Cameras do not display one by default. To view your cameras, refer to your camera’s manual for instructions.
How to use a histogram
Histograms are a way to measure exposure objectively. They’re perfect for those who can’t see very well. Such as in bright light where it’s hard to see an LCD screen. Histograms don’t replace your eyes and experience. The best way to check exposure is to look at the picture, not a histogram. Your eyes are always the final judge. Worry about the image more than the histogram. You are smarter than a histogram. Use it as a guide, not as a template.
The left of a histogram represents dark parts of the picture. The right represents bright parts. Thus, if your histogram has high bars on the left, the picture might be too dark. You might want to adjust the exposure to brighten the picture. If the histogram has high bars on the right, the image might be too bright, and you might want to adjust accordingly.
Benefits of a Histogram
A histogram is helpful is to determine if there are any clipping in the highlights. Overexposure is the death of a digital image. Histograms make this easy to check. If you have clipping areas of 100% white you’ll see a tall vertical line at the far right of the graph. Reduce exposure if you see clipping. Try to get the histogram close to the right side without touching it.
A little bit of clipping is OK sometimes. For instance, highlights from the sun. Clipping broad areas look awful and often shifts colors. This is an art, and you’ll have to learn what looks good to you. There is no law, so don’t worry about being correct.
Overexposed digital images are almost useless. Anything that washes out is gone forever. There is no way to drag Lightroom’s exposure slider to bring back data in the blown out areas.
However, if you shoot in Raw you can bring back details in underexposed areas in Lightroom. Usually an image is underexposed if no lines go all the way to the right. Images that are too dark are easy to correct. In Photoshop or Lightroom drag the exposure slider to meet the edge of the graph.