Stopping down large BinocularsPosted By Roland Christen |
>>"Some thoughts on choosing and using I could clean up the image in my 100mm Oberwerks without loosing to much light gathering and resolution. I put two Orion 120mm objective covers with the center cap's off which stopped my 4" objectives down to 2". >>
With 50mm opening you have approximately 25% of the original light grasp and theoretically only 50% of the original resolution. However, at 20x, you would not see any loss of resolution - the power is too low for your eye to resolve the difference.
As far as light grasp, the only reason that there might not be a dramatic difference is if the original 100mm objectives were internally vignetted by field stops or undersize prisms. In that case, you might have had only 70mm -80mm binos to begin with. Personally, I have examined a number of giant binos at amateur conventions, and found them all to be internally vignetted.
Roland Christen
With 50mm opening you have approximately 25% of the original light grasp and theoretically only 50% of the original resolution. However, at 20x, you would not see any loss of resolution - the power is too low for your eye to resolve the difference.
As far as light grasp, the only reason that there might not be a dramatic difference is if the original 100mm objectives were internally vignetted by field stops or undersize prisms. In that case, you might have had only 70mm -80mm binos to begin with. Personally, I have examined a number of giant binos at amateur conventions, and found them all to be internally vignetted.
Roland Christen
