When preparing images for two color reductions, experiment with emphasizing your Highlights and Shadows, and by increasing sharpness & contrast (via Unsharp Mask & Clarify). A real key is having all images properly prepared prior to running many procedures, special effects, or filters.

This means becoming better acquainted with all your features on the Colors > Adjust menu, along with those Enhance Photo tools on the Effects Menu.

One of the easiest beginner tools for two-color reductions is Highlight Midtone Shadow, on the Colors menu. In fact, that little fella was the only tool I was using exclusively back in PSP5, while learning many favorite tricks. Back then, there weren't any goodies like Curves, Levels, Adjustment Layers, or Enhance Photo tools.  We also didn't have any food to eat.  I was forced to walk barefoot through waist deep snow over broken glass for art supplies. When I eventually did return home, our cable TV only had a measly 80 channels.  Back in '98 life was hell, and you youngsters just don't appreciate how easy you've got it today    :)

Highlight Midtone Shadow: Try increasing the Shadow , while decreasing the setting for Highlight.  Have the LINEAR method ticked.

These days, my favorite tool for this job is Curves.  Kris usually seems partial to the Histogram Adjustment. (see next column), but I personally love my Curves.  Either that version found on the Colors Adjust menu, or its cousin down in the layer palette (also found on the Layers menu under New Adjustment Layer).

New Adjustment Layer: Either Curves or Levels.  The Curves one would be at the very top of my list as the primo tool for playing and tweaking, prior to two-color reductions.  Tweak with Curves, then duplicate the image, reducing that duplicate down to two colors. No need for flattening the duplicate, since our colors reduction automatically flattens at the same darned time. Meanwhile, we've still got the original to experiment and play with. Double-click a New Adjustment layer in the layer palette to re-edit any of your current settings and to make an updated duplicate.   It's easy to whip up a bunch of fast duplicates and to compare the results.

Enhance Photo stuff found on the Effects menu, offers plenty of useful edge enhancement opportunities that work great with this stuff.  That Clarify is a nifty little devil who is absolutely amazing for emphasizing & contrasting many edges prior to two color reductions.

First of all, start by converting your image to greyscale then do your reduction to two colors. Look at the resulting image and see why it is unrecognizable. Most likely it is one (or both) of two things:

(1) the image is not contrasty enough and
(2) the grey shades are wrong.

Item 1 means that if your image is all various shades of grey you won't end up with a dark object on a light background but you'll get dots all over the place.

This can be fixed by compressing midtones in Histogram Adjustment. Item 2 means this. If you have a mid grey of 128 it will be about 50% black dots on a white background after color reduction. If you want more dense dots in that region of the image, you must make the region darker. If you want fewer dots, you must make the region lighter.

The Gamma control in Histogram Adjustment does this. If you want pure white without any dots (say in the image background) use the High Clip Limit control in Histogram Adjustment to make this portion of the image white before color reduction. If you want a solid black somewhere in the image, use the Low Clip Limit to achieve it. One other thing, though it is less useful. If you want to have widely spaced dots throughout your image, you can slide Output Min up and Output Max down in Histogram Adjustment. -Kris

Kris and I frequently travel very different roads to reach similar destinations.  My take on the Histogram Adjustment isn't nearly as precise or clinical - nonetheless, it still yields pretty darned great pictures.  If you are intimidated by all those spinning numbers and choices?  Don't be! Below is an alternative for bypassing a lot of the Histogram Adjustment's techno-mystique.

Snap out of it. Stop all whining, sniveling and cowering.  We all honestly need to make our peace with this incredible tool.  Just keep dragging all your stuff around and watching your previews. It won't be long before all things are revealed.  If you aren't high fiving yourself, and singing "hot damn" by bedtime?  Then you didn't eat the chips, or you uncorked too darned many sodas.  In which case, sober up, and try it again tomorrow.  It isn't complicated at all.  It only looks that way, when we feel intimidated.  Stop peeing those pants.  These are only dials, and they cannot hurt you.  Jump in there to drag them, to spin them, and to drive them around the block.  Look and listen to what your previews are telling you.  Stop skittering around it, and fretting over it.  Just do it -> you'll be glad you did.  -Porter