John Dracon
John Dracon
Without plunging our readers into a virtual wilderness of optical terminology, I have begun to question the de-emphasis given to BK-7 glass as a binocular prism material. In terms of refractive index, it can't match the density of BK-4, of course and hence must be considered as inferior with less light gathering ability. But does this mean that binoculars crafted with BK-7 glass aren't useful and in fact are inadequate in transmitting a quality image to the human eye? I have found to the contrary that some binoculars with the BK-7 glass to perform quite well. I might add that all of these binoculars are built to a high mechanical standard.
I have several of these lower status binoculars that provide a sharp and colorful image, which is virtually indistinguishable from its high status companions. One, a Bushnell 8x30 CF Zeiss clone, at least 60 years old, that functions flawlessly, will out perform any of my alpha glasses of similar power on the resolution charts.
Another, a Bushnell Banner ( recognized as a second tier Bushnell product) CF 6x30 with a 393 foot field came out of a pawn shop for $20. It is at least 60 years old and shows wear. But its coatings are still unblemished, and the sweet spot is quite wide. And the edges are very good. The deep eye cups are easily removed revealing a flat surface which allows the eye glass wearer full view without contacting the ocular surface. Several of my friends have remarked what a pleasing image it presents. It is light, handy, and focuses easily.
Of course both of these binoculars subjected to 30 X magnification will show their optical shortcomings, but for the ordinary persons, these binoculars are adequate. The thought of forking over several thousand dollars for a pair of the alphas, even if cost wasn't an object, is to depart from reality.
It is similar to tire shopping I did the other day. One set was rated to handle sustained speeds of 130 mph with wear rating of 50,000 miles. The other set, which I bought, is rating to handle sustained speeds of !00 mph with a 60,000 wear rating. Since I never drive at either of these speeds, why spring for the higher rated and more costly set of tires?
John
I have several of these lower status binoculars that provide a sharp and colorful image, which is virtually indistinguishable from its high status companions. One, a Bushnell 8x30 CF Zeiss clone, at least 60 years old, that functions flawlessly, will out perform any of my alpha glasses of similar power on the resolution charts.
Another, a Bushnell Banner ( recognized as a second tier Bushnell product) CF 6x30 with a 393 foot field came out of a pawn shop for $20. It is at least 60 years old and shows wear. But its coatings are still unblemished, and the sweet spot is quite wide. And the edges are very good. The deep eye cups are easily removed revealing a flat surface which allows the eye glass wearer full view without contacting the ocular surface. Several of my friends have remarked what a pleasing image it presents. It is light, handy, and focuses easily.
Of course both of these binoculars subjected to 30 X magnification will show their optical shortcomings, but for the ordinary persons, these binoculars are adequate. The thought of forking over several thousand dollars for a pair of the alphas, even if cost wasn't an object, is to depart from reality.
It is similar to tire shopping I did the other day. One set was rated to handle sustained speeds of 130 mph with wear rating of 50,000 miles. The other set, which I bought, is rating to handle sustained speeds of !00 mph with a 60,000 wear rating. Since I never drive at either of these speeds, why spring for the higher rated and more costly set of tires?
John