I had a chance to do a little informal experiment today. I had my annual eye exam, and arrived home with my pupil still dilated to about 8mm.
I like my 7x42 binoculars because they "snap" into focus, and the correct focus is quite obvious. What would happen when my pupil was open wide enough to accept the entire 6mm exit pupil? I found that the no longer snapped into focus and there didn't seem to be a really correct focus. I'd get to a point where they looked almost there, and further motion of the focus knob in that dirrection would just make it worse.
For comparison, I tried my 12x36s. With the smaller 3mm exit pupil serving to stop down my eye's pupil, the correct focus was obvious, although they didn't seem quite as sharp as during normal use. It may well be that I didn't quite have their exit pupil lined up with the center of my pupil where the eye's image quality is best.
Alan
Alan,
Perhaps with your pupil dilated, your vision may have suffered from curvature of field, poor depth of field, chromatic aberration, coma and any of a myriad of other problems exhibited by camrera lenses when they are not stopped down.
Clear skies,
Arthur Pinewood
[QUOTE=Pinewood]Alan,
Perhaps with your pupil dilated, your vision may have suffered from curvature of field, poor depth of field, chromatic aberration, coma and any of a myriad of other problems exhibited by camrera lenses when they are not stopped down.
Clear skies,
Arthur Pinewood[/QUOTE]
If I recall correctly, from a book on Visual Instrumentation, the biggest problem with the dilated eye is astigmatism. Of the Seidel aberrations, it also has the biggest impact on image quality on the retina. The eye certainly works better with a 2 to 3 mm pupil.
Clear skies, Alan