Dynamic range

The "Dynamic range" of the image is the difference between very bright and very dark areas. In the real world, your eye can see very bright and very dark areas by adapting to the light levels, but this does not work on a phone or computer screen. If you take a photo with very light or dark areas, then you may want to deal with the difference. You can't just brighten or darken the whole photo, because that affects both bright and dark areas at once. Instead, you want something that just brightens dark areas or darkens light areas.

If you select the "Dynamic" button, you get a set of sliders.

The first time you move a slider on the dynamic page, it has to calculate a "light map" (see below). This is slow. Once it has processed the whole image, it keeps the lightmap so becomes much faster. So be patient the first time you use it and wait for it to finish, then you can move the sliders as much as you want and it will be faster.

Here is what the sliders do:

The first slider is "Local Colour". What this does is increases or reduces the contrast between neighbouring colours. If you reduce the colour contrast, then you will reduce colour noise, or increase colour details. To be honest, it doesn't work very well!

The next slider is "Range". If you move this to the right, it will darken light areas and lighten dark areas (i.e. reduce the dynamic range). If you move the slider left, it will darken dark areas and lighten light areas. As with lightening shadows, if you do it too much you may need to "Reduce dark colours" on the "Enhance" page to remove colour noise.

The next slider is "Contrast". The contrast on this page is "Local contrast", which means it only emphasizes contrast with nearby pixels. So it looks a bit like a sharpening effect. It will do things like make clouds look more dramatic, as well as emphasize details. If you reduce it, it is a bit like a blur, except that it preserves sharp edges.

The next slider is "Shadows". It brightens only dark areas of the image, so is an easy slider to use if you have excessively dark areas in your image but you don't want to mess up the lighting in the whole image.

The final slider is "Highlights", which darkens highlights, increasing contrast.

There are 2, more technical sliders. All the dynamic effects are based on a "light map". You can increase or reduce the size of the light map, using the "light map size" slider. As the light map gets larger, the amount of processing increases, so it gets much slower. But increasing the size can make some of these effects more dramatic.

The lightmap works out edges of areas. This can be changed using the "light map threshold slider". If you reduce it, then the light map is smoother, but this can create "halos" around the edges of dark or light areas when processing a lot. If you increase it, the halos go away, but you can get some nasty "artifacts". It is set it a reasonable mid-point, but you might want to try altering it to see if it can improve the other effects.