Powerful grain focuser. Adjust the eyepiece so that the etched circle is in focus with your eye in place. Then it's calibrated for your eyesight.
This one is a little rough looking but works fine. I checked it against another grain focuser in the darkroom.
$25 plus postage.
This one is a little rough looking but works fine. I checked it against another grain focuser in the darkroom.
$25 plus postage.