Photographers often use the terms ‘shadows’, ‘midtones’ and ‘highlights’ as if their meaning is obvious. Perhaps it is, but it still probably deserves a little explanation.
One of the issues is that people seldom attempt any proper definition of what these tonal regions are – so I’m going to suggest one.
I think of the bottom quarter of a photo’s tonal range as being the ’shadows’, the top quarter as being the ‘highlights’, and the middle section as being the ‘midtones’.
The image histogram is a key tool in assessing and adjusting these different tonal ranges.
So when photographers talk about ‘lifting the shadows’, or ’shadow’ recovery’ or ‘improving shadow contrast’, they are trying to improve these areas alone without affecting the rest of the photo.
In practice, it’s not really possible to stop shadow adjustments from creeping into midtone areas. The transition between adjusted areas and non-adjusted needs to be smooth in order to look natural. Even so, it is possible target your adjustments principally at the ’shadows’.
Photographers will also talk about ‘improving midtone contrast’, and this is typically done with a curves adjustment or a clarity or dehaze tool. Again, the aim is to improve the contrast in the middle tones without ‘crunching’ the shadows or highlights too much.
It’s the same with highlights. Very often photographers want to ‘recover highlights’ in RAW files where these regions have been slightly overexposed. Again, most software will let you target the highlights for adjustments but you can expect some overlap with brighter midtone areas.
Blacks and whites
Right at the extremes of the photo’s tonal range are solid black and white tones. If the photo doesn’t have and solid black or white areas it can look a little flat and lacking in contrast, so some photo editors offer ‘blacks’ and ‘whites’ sliders for restoring full, solid blacks in the darkest tones and full white in the brightest. You can see these in Lightroom’s Basic panel, for example.
This is much the same as setting the black point and white point in a levels or curves dialog. Photo editors frequently offer similar adjustments with different tools to suit the way different photographers like to understand and work with their photos’ properties.
Lights and darks
As if shadows, midtones and highlights weren’t enough, some programs split up the tonal range differently. Adobe Lightroom’s parametric curves tool, for example, offers ‘shadows’, ‘darks’, ‘lights’ and ‘highlights’ – that’s pretty bad luck if you’re used to thinking about ‘midtones’, but the principle is the same. These are just words to describe a tonal range in the image which is fairly broadly defined and will affect neighbouring ranges to some degree when you adjust it.