In my example I stroke an elliptical selection using the stroke command, using a grey, 30 pixels wide brush.
What ever I do, there is always at least one side of the stroke that is not perfectly smooth. Are there other ways to get a really smooth stroke?

I tried something else: I created one ellipse, filled it with grey, followed by applying "transform selection" while holding ALT+Shift to make the selection about 30 pixels smaller and pressing delete. Using this method I was able to create a smooth ellipse, but then I have a new problem; diameter a doesn't equal b [confused]
Contracting the selection is out of question, because that never gives any smooth result. The only thing that I can do in this situation is to make a small adjustment with "transform selection" before I press delete.

Stroker1

Tangents, 90 degree angles, and theta, don't really agree with things that curve. The math is inaccurate for "clean" results for bigger values of theta.

Grab Rectangular Marque, drag out a rectangle, Select > Modify > Expand, enter 32, and see what happens to the corners. Same basic thing when using Edit > Stroke, even for things that curve.

A good bet is to use a Custom Shape Layer. Make an Ellipse, then a smaller Ellipse set to Subtract. Using the grid is good.

Another excellant option is to Stroke a Path. You can't do inside or outside, but your "diameter" will remain the same all the way around. Make sure to bring the Spacing on your brush all the way down, or else you'll get bumps. It's also fun to stroke a path several times with various brushes.

Of course man of all strokes Stroker, I should use paths, silly of me not to think of that one. Thanks [righton]

Stroker1

LOL!
To add to that, my first formal tutorial is called "Multi-Stroking a Path". It's over a Gurus' Network's PS tuts section (currently DNS problems, so you might not be able to get to it).

Another use for Multi-Stroking a Path is swervey laser-type stuff. A big soft Airbrush with one colour, then a smaller Airbrush with another colour. Very cool.

Good that you mention that one Stroker. I've visited that site a couple of times, but only now that "multi-stroking a path" is getting my attention. I will have a look at it tomorrow. Thanks again.