Tests for digital imaging tools and more

"What actually happened to my image?" - if you ask yourself the above question from time to time after some tool or filter has changed your image the right or the wrong way, then this is the place to come to.

In this section you will find - among other things - tools for testing other tools that cause global tonal value and local contrast changes, that means tools from the first and second category on the right. Measuring and visualizing color changes produced by tools from the third group is more complicated, separate tools may follow later.

Counting image colors
Sometimes it is useful to know the number of colors in an image. More...
Measure gradation shifts
Tools for measuring changes in gradation. More...
Measure sharpness and softness
"Contrast curves" for measuring shifts in contrast along the edges of an image. More...

Tests for digital cameras

With the help of adequate test images many camera characteristics can be determined with an accuracy sufficient for most purposes. Verify and compare the sharpness and resolution of your camera and lenses, determine dynamic range and shooting characteristics of your digital camera.

Sharpness and resolution
A test image consisting of several fine and large patterns permits visual examination of sharpness, resolution, distortion and chromatic aberration. More...
Dynamic range and Shooting characteristics
How big is the dynamic range of your camera? Is there a contrast boost already internally applied? More...

Printer Tests

Three Test images for verifying gradation, color, resolution and profil quality of desktop printers. More...

Three ways to change an image:

1. Global changes of tonal values

Tools of this category change tonal values independently from the original pixels' luminance and chrominance values. For example, all tools of the first group in the Photoshop menu Image/Alter (Brightness/Contrast, Levels, Curves, Color Balance, etc.)

2. Local changes of contrast relative to original contrast

To this group belong tools that primarily alter the edges of an image, i.e. sharpening and blur tools.

3. Color-specific changes of tonal values relative to the original color

This group covers color correction tools like Hue/Saturation and Selective Color, but also the Channel Mixer (second group in the Photoshop menu). It doesn't cover Color Balance, because this tool is working globally (like Brightness/Contrast) without taking care of the original color.