What is an RGB histogram?
It’s not just the overall brightness that you can check, but the strength of the colours too
In addition to a brightness or ‘luminance’ histogram, you can also view an image’s RGB histogram. As the name suggests, this enables you to see separate histograms for the red, green and blue primary colour ‘channels’ that make up the digital picture.
Being able to judge the strength of each of these colours separately is useful, as even when the brightness histogram shows a ‘perfect’ exposure, one of more of the colour histograms may be clipped. As with the brightness histogram, it’s best to avoid clipping a colour histogram on the right, as the colour will be oversaturated and you may lose fine detail in some areas of the picture.
The brightness histogram typically mirrors the shape of the green histogram, so it’s worth checking the RGB histogram if the subject of your photo contains a lot of red or blue.
Clipping Here, the brightness histogram looks fine, but the red channel is clipped.
Check the colours The brightness histogram (shown at the bottom) follows the shape of the green histogram most closely.