How do you transform a picture into something purely black and white, without gray?

without photoshop on me at the moment, you could select Image-Brightness/Contrast, and then drive the contrast to its maximum. that would yield a comp[letely black and white image so long as the image was already put in grayscale mode. After that, messing with the brightness and whatnot to get different levels andwhatnot. mess around mah friend.

you could desaturate your image or convert it to black&white and then use (image>adjustments>)posterize, with a value of 2 for levels... or use (image>adjustments>)threshold for more precision... but if you want to have a halftone pattern you have to convert your image to black&white (desaturate doesn't work in this case...) and then go to filter>pixelate>color halftone and click ok... then you could have grey things like shadows, but still the image is purely black and white... i hope this helps... grd

There is a short cut. It is also available as correction layer. I think it is called 'threshold' (in Dutch it is called 'drempel', nice eh?) It does the same as posterizing, but then with a nice slider. The transition will be harsh. Stuff like this tend to look better when you do it via Streamline (also Adobe), which converts your photographs into nice vectors. In combination with Illustrator you are on the way to annoy another pack of teeth-grinding artists that used to do this kind of stuff for a living. By hand. Recoloring it is even more fun.

i already mentioned threshold ;) enneh... drempel klinkt zo stom... vind je niet? grd

Try Filter-Sketch-Photocopy Then Filter-Sharpen-Unsharp Mask. Here max out everything but leave Threshold at 0. I tried it on a photo and it works nicely.

line art kicks

heh. filtering something can hardly be called line art.

try using the bitmap mode under image-->mode. i think that's what ur looking for. it halftones the image using pure black pixels on pure white. later on you could change the mode back to RGB or CMYK to fiddle about with colours and other effects.

^^^ the bitmap ^^^