What does 'tolerance' mean?

If you use the magic wand and select 'tolerance' to be 32, I would think all adjacent pixels within an absolute RGB-difference of maximum 32 would be selected.

This is not true. According to one tutorial 'all pixels of at most 16 shades lighter or darker (16+16=32) are selected.'

My question: All pixels in an image have an RGB-value, but how does this correspond to the 'lighter/darker' of previous statement. Reformulated: what does the tolerance of the magic wand actually mean?

Hope to be not too technical for you guys,

Daan

The values refer to the RGB values: each color, in a 8 bit image is referred to a 0-255 scale on three color channels. It will select colors that are maximum 16 units lighter or darker, in EACH channel.

Create a white document, put gradients at different angles in each channel: one vertical, on horizontal, one diagonal. set tolerance to 32, and select. deselect, apply some posterizations to one channel, then repeat the game... Also pay attention to the settings of your eyedropper tool, and the contiguous option of the magic wand...

I've done that, Spectre. I created 5 overlapping squares of a color each. The colors varied 16 to 32 on one or three RGB registers. I clicked the central square, and the magic wand selected everything up unto 32 values DOWN. So it must be something else.

By the way: I am talking Photoshop 7.

Daan