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Zeiss Sonnar f2 5cm collapsible with coated glass (???)
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PostPosted: Wed Jun 17, 2015 6:23 am    Post subject: Zeiss Sonnar f2 5cm collapsible with coated glass (???) Reply with quote
A friend of mine owns a Zeiss Sonnar f2 5cm collapsible lens with serial number indicating that it has been made during pre-war. The strange thing about that lens is that I can clearly see some sort of coating on the front element. How can that be?
The body for sure is not some sort of fake, but the pre-war glass of that sonnar is for sure uncoated. Could it be that the front element has been replaced with one from a Jupiter lens, is that possible? Could it be that the glass has been sent for coating?


PostPosted: Wed Jun 17, 2015 10:57 am    Post subject: Reply with quote
Three possibilities I can think of...

1. A prior owner has had the lens coated. I believe that there were commercial services post war that did this.

2. The glass has developed a 'natural' coating. I have read about this process and how it may have led to the eventual development of coated lenses.

3. The possible replacement of the original glass with later coated glass.


PostPosted: Wed Jun 17, 2015 11:07 am    Post subject: Reply with quote
Would it be possible that a front element from a Jupiter-8 has been used? Are the optics of the J-8 and the original CSJ interchangeable?


PostPosted: Wed Jun 17, 2015 11:18 am    Post subject: Reply with quote
The original '3K' Contax mount J-8s were made with Zeiss components and glass. I think that when the Schott glass ran out it would have been easier for the Soviets to produce their own glass to fit the current lens rather than change the lens design to accept a different lens.

I am certainly no expert but I have read that these lenses were pretty much a matched set. It would be easier to replace the entire optical block than to find a front lens to mate with a different block.


PostPosted: Wed Jun 17, 2015 11:20 am    Post subject: Reply with quote
Zeiss produced T coated lenses quite early, what is the serial number of the lens?

The Russians had to recalculate the Jupiters to take account of the different glass types available, but the changes were really minor so probably a J8 front glass would fit no problem.


PostPosted: Wed Jun 17, 2015 11:56 am    Post subject: Reply with quote
Coating started early perhaps from 1936 Berlin Olympic Game, I have this lens too with T


PostPosted: Wed Jun 17, 2015 6:00 pm    Post subject: Reply with quote
The lens has the serial number 1986559


PostPosted: Fri Jun 19, 2015 11:20 am    Post subject: Reply with quote
Wink

Quote:
It was noticed by Dennis Taylor in 1896 that some lenses with glass tarnished by age counterintuitively produced brighter images. Investigation revealed that the oxidation layer suppressed surface reflections by destructive interference.[98][99] Lenses with glass elements artificially "single-coated" by vacuum deposition of a very thin layer (approximately 130-140 nanometers[100]) of magnesium or calcium fluoride to suppress surface reflections were invented by Alexander Smakula working for Zeiss in 1935 and first sold in 1939.[104] Antireflection coating could cut reflection by two-thirds.[105]

In 1941, the Kodak Ektra (USA) 35mm RF was introduced with the first complete antireflection coated lens line for a consumer camera: the Kodak Ektar 35mm f/3.3, 50mm f/3.5, 50mm f/1.9, 90mm f/3.5, 135mm f/3.8 and 153mm f/4.5.[106] World War II interrupted all consumer camera production and coated lenses did not appear in large numbers until the late 1940s. They became standard for high quality cameras by the early 1950s.
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