In this tutorial, we tackle Halide’s incredibly powerful and feature-packed histogram. What is a histogram, exactly? It’s simply another tool in your photographic arsenal for ensuring a proper exposure.
To enable the histogram, tap on the little bar graph icon in your quickbar. The histogram will appear in the top left corner.
You can tap the histogram icon again to make the histogram larger. Tapping it again will turn it off.
The histogram might seem a bit foreign to you if you’ve never used one before. In order to understand the histogram, think of it as a way to view the image’s range of exposure, with the leftmost portion being your image’s shadows, and the rightmost portion being your highlights.
What you want to avoid is tall bars on one side.
If you’re losing details in your highlights, you’ll have a lot of tall bars to the rightmost side of the histogram. If the image is too dark and you’re losing information in the shadows, the histogram will have a lot of left-leaning bars. If the leftmost or rightmost bar is much larger than the other bars, it means you are "clipping."
A perfect exposure should have all the bars pretty evenly sized. That can't always happen, and we'll talk about why in a future tutorial. But if you can adjust your exposure to even them out, you'll be much happier when you go to edit your photo later.
Try playing with the exposure adjustment gesture you learned in an earlier tutorial —simply swipe up and down on the viewfinder— while the histogram is on and see how it reacts to bright or dark images to get a better understanding of what the histogram does.
Pro Tip: You can also tap the histogram itself (instead of the icon) to change its display mode. There's a luminance histogram (that means just light and shadow), a color histogram and an RGB waveform display.
In our next tutorial, we'll dive into White Balance.