I'm not sure exactly what triggers it, but when I paint in Photoshop 7 sometimes the brush size will stop responding to my pen pressure (i.e. the brush size will remain constant).
Occassionally I get the problem after alt-tabbing out of Photoshop, but this doesn't happen 100% of the time so I am not sure. I was wondering if maybe there's a hotkey I'm pressing that's killing the pressure sensitivity? Or if there's a quick way to restore it without having to restart Photoshop.
By the way I experience this problem using both my Intuos3 and Graphire3 in Win 2000, XP, and ME. So I'm pretty sure the problem is Photoshop 7.
You could be causing the problem with the Alt-tabbing out of PS.
PS retains cache memory that can snafu things if you don't exit "cleanly" out of PS. Add to that a drawing tablet with its own ideosyncracies, and you may be asking for trouble.
I run 7.01 with 9x12 Intuos and Intuous2 tablets, and have NEVER had that problem.
You might also be sure that you have the Shape Dynamics box checked in your Brush Palette...
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I have this problem also sometimes...i fix it by changing to flash and drawing some brush strokes there...the pen gets it's pressure behaviour again in ps then...or if you don't have another software with pressure sensitivity it works also when clicking the checkbox on the brush settings where it sais pressure sensitivity...using CS2, so i don't know if it will work on PS 7...