Digital Light & Color

I had an image that I was working on recently, in which the dynamic range, as shown in Levels and Colour, was (can't recall exact numbers but...) 30% and 60%.

Wishing to maintain the same dynamic range but brighten the image, I merely moved the Brightness slider to the right.

Once complete, however, the dynamic range was not the same 30% difference (quite a bit different, actually) between the lightest and darkest points. As I was not nearing either clipping point, is there a reason why the difference between lightest and darkest tones would not remain static?

Marv

The dynamic range in Levels and Color is approximate since it does not work on the lightest and darkest pixels. If it worked that way, a single white or black pixel, while likely invisible in the image would set the white or black points. Instead, it averages the brightness of the brightest 0.01% and the darkest 0.01% of the pixels to locate the white and black points. When you adjust the brightness, this can change their values although usually not by much.

Jonathan,

Thanks for the explanation.

Out of curiosity, I found the image that spawned my post and ran it through the Brightness transform again, whilst recording the numbers.

Start - DR 37.3 and 74.9 (difference of 37.6).

Moved Brightness slider to 76.3% and DR numbers now 78.4 and 96.9 (difference of 18.5).

Just thought the difference was worthy of an explanation.

Thanks again,

Marv

If you can email me the image, I can take a look at it.

You can get better control over the dynamic range and brightness using Adjust instead of Levels and Color as it uses a curve instead of sliders.