Optical Mouse Navigation

[Craig Putnam]

Originally Posted by Alan Anderson

... However, raising the mouse by a couple of millimeters decreased the measurement to about 380 counts. Lowering it a similar amount increased it to about 440. ...

It sounds to me as though you had very little depth of field. Think of a completely manual camera (I know - that sets a lower boundary on my age!). You have to set the f-stop & shutter speed to get a correct exposure. You can trade them off back and forth as necessary to get the effect you desire.

Want more depth of field? Then stop down the lens (increase the f-stop). Because there is less light coming through the smaller aperature, you need to more brightly illuminate your subject (if you can) or decrease the shutter speed (and risk camera shake).

I suspect I've got a much smaller aperature (higher f-stop) and therefore more depth of field than you had in your setup. Now, I don't have a *lot* of headroom vertically - perhaps +/- 5 mm at the moment, but I can increase it if I need to by stopping down further (I have more light than I need and can always add more if necessary).