bitmap icons

(SOLVED) Optimizing a font for a clear pixel display at 8 pt size. How?


Dear Typophile members.
I'm compiling some letters (drawn by someone else) into a font. The letters are meant to be used in icon bitmaps sized 24 x 24 pixels and the characters were drawn to match this grid. However the result should not be a pure black/white pixel font but should show some gray tones as well. Please see attached image (desired look).
I made the font in TypeTool. The trouble is, I can't produce the right look in Photoshop when using the font. I use 8 pt size.
The UPM is 1024 and each pixel is 128 units (8 x 128 = 1024). Also every letter spacing is 128 units.

Clearly I'm doing something wrong. Does anyone know how to do this right?

Many thanks!