That's probably a 2400dpi halftone (or similar) resolution. To compare to ppi (pixels per inch), you need to decide how many gray levels you want. Assuming th

That's probably a 2400dpi halftone (or similar) resolution. To compare to ppi (pixels per inch), you need to decide how many gray levels you want. Assuming the 2400dpi is a grid, and you want >= 256 shades, you need a grid square of 256 dots (16x16). This is all rather handwavey though, as two-tone b+w prints truly would be 2400dpi. So 2400dpi might be comparable to 150ppi for photographic images.