Legendary binoculars - Carl Zeiss Jena Deltrintem 8x30 (1 Viewer)

[Arek]

You might be interested in reading this:
http://www.allbinos.com/index.php?art=170

Greetings!
Arek

 

[Troubador]

Hi Arek

Happy New Year.

The link isn't working though......

Lee

 

[gunut]

very nice article.....thanks

 

[james holdsworth]

I find it hard to believe that a porro from 1978 was hitting 92%, at any wavelength. I have a 8x30 Zeiss West from 1978 and don't know its transmission, but in comparison to modern glass it looks like somewhere in the 70% - 80% range. Compared to a modern roof, like my 8x32 Conquest HD, the side-by-side difference in transmission is stark, and the HD isn't likely hitting 92%.

 

[Arek]

32 vs 30 mm gives 14% light more only due to the aperture difference.

Multicoated Jenas were still optimized for centrum of visible spectrum and transmission level of 90% was reached only there. If you average transmission in wider range of wavelenghts, the total amount of light delivered to the eyes of the observer is lower than in modern binoculars with much more flat transmission curve.

 

[Troubador]

I find it hard to believe that a porro from 1978 was hitting 92%, at any wavelength. I have a 8x30 Zeiss West from 1978 and don't know its transmission, but in comparison to modern glass it looks like somewhere in the 70% - 80% range. Compared to a modern roof, like my 8x32 Conquest HD, the side-by-side difference in transmission is stark, and the HD isn't likely hitting 92%.

Oddly enough James, Gij's figures show Conquest HD 8x32 just hitting 92% at about 550nm. See the pic.

Quite a surprise to me too.

Lee

 

[james holdsworth]

Well, I may be totally wrong but the transmission figures I have seen for older porro's have been in the 70% percent range, so I'm really surprised by the Deltrintem's figure. How would this transmission rate as an percentage average over the visible spectrum?

 

[henry link]

Arek,

I'm also curious about the very high peak light transmission of the multicoated Deltrintem from 1978. Can you suggest a reason why it measured so much higher than the 7x50 Jenoptem from the "end of the 80s" in the article below? Presumably both used T3M multicoating.

http://www.allbinos.com/160.1-artic...lars_and_lenses_Colours_and_transmission.html

When was the Deltintem measured? You may be aware that some of the Allbinos light transmission measurements from 3 to 5 years ago have been questioned here as being too high.

Henry

 

[jring]

Hi,

I have some doubts about the transmission graphs in allbinos otherwise nice reviews... they vary quite a bit when they should be similar and sometimes are just too good to be true...

@james: a Zeiss West from 1978 might well be single coated only - does it say T* anywhere on the bins or in the paperwork? And an old porro like the Habicht 8x30 reached 96% transmission in the Swaro lab and with Gijs - ok, they did upgrade the coatings ;-)

Joachim

 

[henry link]

AFAIK unfortunately none of the Zeiss West Porros were T* coated, except for the two models that continued in production after 1978: the 7x50 and 15x60. My T coated 8x30 B from about 1970 is certainly not bright by modern standards, even after a thorough internal cleaning by Zeiss.

As Joachim says, new 8x30 Habichts are superbly bright. With the latest Swarovski coatings, prisms with total internal reflection and only 12 glass to air surfaces, how could they miss?

Henry

 

[Troubador]

Well, I may be totally wrong but the transmission figures I have seen for older porro's have been in the 70% percent range, so I'm really surprised by the Deltrintem's figure. How would this transmission rate as an percentage average over the visible spectrum?

James, just in case you misread my post, it concerned the Conquest not Deltrintem.

Lee

 

[james holdsworth]

James, just in case you misread my post, it concerned the Conquest not Deltrintem.

Lee

Thanks, Lee, I got that but still question the peak trans of the Deltrintem.

 

[Arek]

Arek,

I'm also curious about the very high peak light transmission of the multicoated Deltrintem from 1978. Can you suggest a reason why it measured so much higher than the 7x50 Jenoptem from the "end of the 80s" in the article below? Presumably both used T3M multicoating.
Henry

Deltrintem 8x30 was from 1985, not from 1978.

Jenoptem 7x50 and Deltrintem 8x30 (both with T3M coatings) were measured using the same equippment. The differences in transmission might come from different specimens and also from absorption of the light in glass. Bigger 7x50 model indicates thicker lenses and prisms and higher absorption.

 

[jring]

Hi,

absorption in optical glass is negligible in comparison to reflection even the with best multicoatings.

Joachim

 

[henry link]

Yes, comparing internal absorption between these two would be an exercise in hair splitting. The loss through 25mm of BaK-4 is only about 0.4% at 550nm. There might be about that much difference in the thickness of the prisms between the 7x50 and 8x30. The thickness of the lenses is probably about the same since the Deltrintem has an extra cemented doublet in the eyepiece. The extra 2 glass to air surfaces in the Deltrintem eyepiece probably cause more loss than any extra absorption in the Jenoptem prisms.

 

[LPT]

The Deltrentis/Deltrintem binoculars when introduced in 1920 did, in fact, have 3 lens/5 element Erfle eyepieces. Hans Seeger in his most recent (2015) book, "Zeiss-Feldstecher Handferngläser von 1919-1946. Modelle-Merkmale-Mythos" - pages 144-151, examines this subject in detail. He shows that from 1920-1926 these model binoculars used a 3 lens/5 element Erfle type eyepiece very much like the second one presented in the Albinos' article; from 1926-1932 a modified 3 lens/6 element Erfle was utilized; and, then from 1932-1946 the 2 lens/ 4 element eyepiece shown first in the Albinos' article was introduced which, interestingly, had an aspheric middle (facing the objective lens) element. So when, in 1947, Zeiss Jena modified the binocular to have a 3 lens Erfle, they were actually reverting to the original 1920 design.

 

[Troubador]

The Deltrentis/Deltrintem binoculars when introduced in 1920 did, in fact, have 3 lens/5 element Erfles eyepieces. Hans Seeger in his most recent (2015) book, "Zeiss-Feldstecher Handferngläser von 1919-1946. Modelle-Merkmale-Mythos" - pages 144-151, examines this subject in detail. He shows that from 1920-1926 these model binoculars used a 3 lens/5 element Erfle type eyepiece very much like the second one presented in the Albinos' article; from 1926-1932 a modified 3 lens/6 element Erfle was utilized; and, then from 1932-1946 the 2 lens/ 4 element eyepiece shown first in the Albinos' article was introduced which, interestingly, had an aspheric middle (facing the objective lens) element. So when, in 1947, Zeiss Jena modified the binocular to have a 3 lens Erfle, they were actually reverting to the original 1920 design.

Thanks for posting LPT, its fascinating stuff.
Lee

 

[Binastro]

Was the 1932 eyepiece lens element hand or machine aspherised?

There were Zeiss machine lens aspherics on a fast f/1.9? Tessar in the 1930s.
The machine had been invented earlier by someone else.