Thanks. Interesting. It sounds like glass quality can play a big part in it.
Was there text to describe how the measurements were taken, equipment, etc.?
Ed
Wow! I never knew there was much to consider with just glass. So all glass and all lenses are not the same.
Dennis, post 16,
I have looked in our files and between the different porros made between 1945 and 1980 by different companies (e.g. Beck, Bush, Goerz, Kern, Möller, Voigtländer, Wöhler, Wollensak, Bausch and Lomb, Leitz, Zeiss, Krombach, Minolta, Pentax, Hertel & Reuss, Nickel,, Nitschke, Swarovski , Bleeker, Oude Delft-Delft Instruments, Tento, Komz, Konica) between 1945 and 1980 quite a few had transmissions from below 50% up to 80% and all values in between.
As Binastro in his post 18 already has explained a number of factors can be the cause of it.
Gijs van Ginkel
But 0.95 to the tenth power is 59.8% i.e. 60%, and 0.96 to the tenth power is 66%.
According to google, as I am tired and cannot be bothered to do the calculation on paper.
Thanks. So they must have really high quality glass, a lower number of optical surfaces, excellent coatings and a short light path. Good to know. So the Habicht's transmit better than say the Nikon SE and EII because of better glass quality, number of optical surfaces, better coating quality and a shorter light path?Dennis, post 31,
That is a combination of optical glass quality, amount of optical surfaces, coating quality and distance light has to travel through the optical glass components.
Gijs van Ginkel
Thanks. So they must have really high quality glass, a lower number of optical surfaces, excellent coatings and a short light path. Good to know. So the Habicht's transmit better than say the Nikon SE and EII because of better glass quality, number of optical surfaces, better coating quality and a shorter light path?
It looks like their is quite a bit of glass in the Habicht's. From Scopeviews Habicht 10x40 Review. http://scopeviews.co.uk/Swaro10x40Habicht.htmI'd say the main factor is the Habicht's multi-coatings i.e. their quality including the number of layers of multi-coating. Also, how many lenses are there in the Habicht Porro I models' eyepieces? Offhand, I think they have relatively narrow fields of view compared to other Porros which may indicate a non-wide angle type two lens eyepiece while the other Porros like the EII and SE may have a 3 lens eyepiece. If I'm correct about this, # of air to glass surfaces would also be a main factor. Would be interesting to see schematics of some of the eyepiece builds of the Habichts, SE's and EII's.
Henry, thanks for the explanation! If their are 12 glass to air surfaces in the Habicht and Scopeviews says they have the same glass as the Swarovski EL's and probably the same coatings why do the Habicht's still have 5% better transmission than the EL's? Does it have something to do with the more efficient fully reflective porro prisms of the Habicht versus the less efficient phase corrected roof prisms of the EL?The very same 6 element, 3 group Erfle (patented in 1923) is used in both the 8x30 and 10x40 Habichts. There are 12 glass to air surfaces total. The Nikon SE and EII have six element eyepieces, but in a more modern 4 group design, so 14 surfaces total. The Swarovski Porros with the fewest surfaces were the 7x42, 7x50 and 8x56 SLs with 3 element, 2 group Konig eyepieces and cemented prisms, only 8 surfaces.