henry link
Well-known member
Speaking as the guinea pig who tried to conduct a controlled test of some of brock's ideas about CA in low power binoculars I feel it's my duty to warn the innocent that I was NOT able to see any effect whatever on CA that could be attributed to the removal of lead from optical glass.
I should mention that I can see plenty of lateral color in my test set-up. Its white against black pattern of bars is specifically designed to maximize the appearance of color fringes. The binoculars are compared tripod mounted next to each other and the CA target's white bars are placed at 2 degree intervals, so I can be certain I'm comparing CA at exactly the same spots in the field. I reported a VERY tiny difference in lateral CA between an old single coated Nikon 8x30E and a later 1992 multi-coated version. Between that 1992 binocular with lead and a 8x30 EII with Eco-glass that I purchased in 2006 I saw no difference in lateral color at all. I mixed and matched eyepieces and objectives between the E and the EII and still found no difference.
Today, after reading the posts above I decided to repeat the test between the single and multi-coated E's. This time, I couldn't even repeat the tiny difference I reported earlier and that's between binoculars with perhaps 15-20% differences in light transmission. How much tinier would the difference in CA be between slightly tweeked multi-coatings with only a few percent difference in light transmission?
I know nothing I can say or do on this subject will matter to the true believer. Besides, I don't have anything new to add and I'm reading the same stuff I've read many times before from brock, so I'll just withdraw now and take my licks.
I should mention that I can see plenty of lateral color in my test set-up. Its white against black pattern of bars is specifically designed to maximize the appearance of color fringes. The binoculars are compared tripod mounted next to each other and the CA target's white bars are placed at 2 degree intervals, so I can be certain I'm comparing CA at exactly the same spots in the field. I reported a VERY tiny difference in lateral CA between an old single coated Nikon 8x30E and a later 1992 multi-coated version. Between that 1992 binocular with lead and a 8x30 EII with Eco-glass that I purchased in 2006 I saw no difference in lateral color at all. I mixed and matched eyepieces and objectives between the E and the EII and still found no difference.
Today, after reading the posts above I decided to repeat the test between the single and multi-coated E's. This time, I couldn't even repeat the tiny difference I reported earlier and that's between binoculars with perhaps 15-20% differences in light transmission. How much tinier would the difference in CA be between slightly tweeked multi-coatings with only a few percent difference in light transmission?
I know nothing I can say or do on this subject will matter to the true believer. Besides, I don't have anything new to add and I'm reading the same stuff I've read many times before from brock, so I'll just withdraw now and take my licks.
Last edited: