I said:
"We sometimes discuss how a Schmidt-Pechan prism is not totally internally reflective at all surfaces, and generally applaud the new dielectric coatings which give over 99% reflectivity, enabling the SP to compete with Porros and AKs for brightness.
But, isn't the reflectivity of a phase-altering coating, like on top roof prisms of either style, an issue too?"
Surveyor said:
"RonH,
You may find this a fair starting point. http://www.mellesgriot.com/products/optics/oc_2_4.ht"
Thanks Ron. While that doesn't exactly spell it out, I surmise that phase coatings are a special type of dielectric multicoating. And, since phase coated roof prism binoculars now deliver throughput comparable to the best Porros, it is clear that these coatings which among other things reflect light, must be very efficient indeed regarding reflectivity. This seems like a cheerful optical fact on the surface, doesn't it?
But it makes me feel bad. Somebody say it isn't so. Let me explain.
In 1990 Leica gave us a breakthrough binocular, the Trinovid, which among other advancements was the first generation of phasecoating, called the "P40", for its 40 layer structure, which I believe Leica still uses, in its highly transmissive current model, the HD. ( Zeiss had been first, with the AK-prismed BGA/T*.)
What burns my biscuit is if Leica could do that, an impressive feat of dielectric multiwitchcraft, it apparently at that time had the ability to do a 99+% dielectric on the other SP surfaces, which would have made a much brighter binocular than the 83% transmission BA which they put out. But, didn't.
Now the confessional part. I loved an 8x42 Trinovid BA and now I am all torn up. I could live with the lurchy focus, high weight, and cramped ergonomics. I adore the macho appearance and feel, and prize the reputation for quality and ruggedness. I recognize that the CA is relatively unobtrusive, a good step less noticeable than many other top binoculars including the Swaro EL. I find the comfort and immediacy of the view, the field correction, the sharpness, and the contrast, exemplary. What really keeps it sitting on the table while my Zeiss FL goes out birding is its dimness. Which I suspect didn't have to be-- Leica may not have given its best.
The Zeiss is actually better in important and objective ways, to be honest. CA is virtually gone, it is feather light, easy to grasp and focus, bright as a Fujinon Porro. But it just doesn't have much character. I wonder if Leica would replace the silver coated prisms with dielectrics--some have said that the cut of the glass is the same as the Ultravid.
Somebody must have loved Janis Joplin too, and wondered if there was a rehab that could straighten her out. Not to be. She was who she was. Maybe all it is is, true love can only happen once.
Ron
"We sometimes discuss how a Schmidt-Pechan prism is not totally internally reflective at all surfaces, and generally applaud the new dielectric coatings which give over 99% reflectivity, enabling the SP to compete with Porros and AKs for brightness.
But, isn't the reflectivity of a phase-altering coating, like on top roof prisms of either style, an issue too?"
Surveyor said:
"RonH,
You may find this a fair starting point. http://www.mellesgriot.com/products/optics/oc_2_4.ht"
Thanks Ron. While that doesn't exactly spell it out, I surmise that phase coatings are a special type of dielectric multicoating. And, since phase coated roof prism binoculars now deliver throughput comparable to the best Porros, it is clear that these coatings which among other things reflect light, must be very efficient indeed regarding reflectivity. This seems like a cheerful optical fact on the surface, doesn't it?
But it makes me feel bad. Somebody say it isn't so. Let me explain.
In 1990 Leica gave us a breakthrough binocular, the Trinovid, which among other advancements was the first generation of phasecoating, called the "P40", for its 40 layer structure, which I believe Leica still uses, in its highly transmissive current model, the HD. ( Zeiss had been first, with the AK-prismed BGA/T*.)
What burns my biscuit is if Leica could do that, an impressive feat of dielectric multiwitchcraft, it apparently at that time had the ability to do a 99+% dielectric on the other SP surfaces, which would have made a much brighter binocular than the 83% transmission BA which they put out. But, didn't.
Now the confessional part. I loved an 8x42 Trinovid BA and now I am all torn up. I could live with the lurchy focus, high weight, and cramped ergonomics. I adore the macho appearance and feel, and prize the reputation for quality and ruggedness. I recognize that the CA is relatively unobtrusive, a good step less noticeable than many other top binoculars including the Swaro EL. I find the comfort and immediacy of the view, the field correction, the sharpness, and the contrast, exemplary. What really keeps it sitting on the table while my Zeiss FL goes out birding is its dimness. Which I suspect didn't have to be-- Leica may not have given its best.
The Zeiss is actually better in important and objective ways, to be honest. CA is virtually gone, it is feather light, easy to grasp and focus, bright as a Fujinon Porro. But it just doesn't have much character. I wonder if Leica would replace the silver coated prisms with dielectrics--some have said that the cut of the glass is the same as the Ultravid.
Somebody must have loved Janis Joplin too, and wondered if there was a rehab that could straighten her out. Not to be. She was who she was. Maybe all it is is, true love can only happen once.
Ron
