I need to make a grating (equal width black and white stripes).  So far I have gotten them down to 12 black stripes per centimetre, but I’d like to have it down to 16 or so.By trial and error I’ve been doing it this way: fill the screen with a gradient tool (black), and then Filter>Distort>Wave, settings set to: type-square, generators-999, wavelength-12/12, amplitude-999/999, Scale-100/100, Repeat edge pixels.  I’m using high contrast (as black as possible), but eventually I will vary the contrast.-Is there a way to make the stripes thinner?  -What do the settings mean?  I’m using it to check animals' vision.  Thanks!