Tonal range
The tonal range indicates how much color information an image or image file contains. It describes the difference between the lightest and the darkest part of an image. The tonal range is specified in relation to the maximum possible range, for example from 5% white to 93% black.
The maximum tonal range ( color space ) is limited by the medium, in the case of photographs the properties of the selected photo paper or printing process, in the case of digital graphics by the color depth of the graphic format used and the technical possibilities of the playback device such as a screen .
In order to enable a differentiated and high-contrast reproduction of an image, attempts are usually made to optimally utilize a color space , but there is also a deliberate reduction in the tonal range in order to achieve special effects such as in high or low key photography.
The tonal range of a digital image can be regulated with image processing software . Not only can the maximum and minimum values be changed, but also the statistical distribution of the tonal values in the image. The tonal value correction is therefore the most important tool for optimizing brightness and contrast . The histogram serves as an aid to analyze the distribution of the tonal values, which can then be specifically corrected. With a strong increase in the tonal range, however, quality losses can also occur if there is a visible spread of the tonal values, as a result of which fine color gradients can no longer be reproduced homogeneously.
Web links
- Tone values, histogram and tone value curve. Introduction to digital tonal value correction on ScanDig.eu