tunalegs
Pretended Artist
I think they're referring generically to glass bloom, which has nothing to do with polishing, and depends more on the composition of the glass and how it has been stored.
sevo
Fokutorendaburando
I suspect that references to glass bloom are so widespread as iridescent decorative glassware was massively popular in the decade following the discovery of King Tut's grave. I still have to find proof of a single genuine naturally "bloomed" but otherwise functional lens - there can't be many atmospheric conditions that etch glass but do not corrode metal to destruction. Usually "bloomed" refers to the chemical coating TTH used between the wars (but that was a popular descriptive term, not a technological one).
oltimer
Well-known
Great lens you got there, and a real "keeper". Frank Mechelhoff will spot this thread soon enough, as he has done much write-ups on Sonnar design.Sevo, I took a turn at it and yes, I managed to unscrew the adapter.
Larry H-L
Well-known
Is it rangefinder coupled, or scale focus?
chambrenoire
Well-known
Rangefinder coupled, actually.
uhoh7
Mentor
http://photo.net/nikon-camera-forum/00CPgZ
See the second post in that thread, where Robert Lai states:
"In the days of uncoated glass, the apocryphal lore is that a researcher noted that very old lenses had higher transmission of light than brand new lenses. The answer was that old lenses had been exposed over time to the halogens in the atmosphere, and had acquired a "coating" of its own. This lead to research that allowed single layer coating of lenses. Zeiss had this as a patented secret, and it allowed them to build the best lenses in the world (late 1930s?). They were even better than Leica at the time, as Leitz hadn't figured out about lens coating."
"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"
wikipedia
Henry Scherer certainly believes this is true as he instructed me to not clean my uncoated czj 50/1.5 from 1937 which he had repaired, for exactly this reason.
He does seem to know a lot about old zeiss glass:
http://www.zeisscamera.com/services_overhaul-cIIa-lenses.shtml
Here is what he wrote to me:
"Hello Charlie,
I have an opening while waiting for paint to cure while working on a Contax III and so have moved forward with your lens and it is completely disassembled. It is very dirty but very fine. The lens elements are in perfect condition and so my guess is it's going to be a 10 when its done. It's distinguished by very fine surface oxidation of the front and rear lens elements. This shows it's never been cleaned. Whoever owned it previously cared for it very much. This surface oxidation acts like coating and significantly improves the lens so if I were you I'd invest in a UV filter and would never clean this lens. This surface oxidation is very rare and highly desirable."
From the 1973 amateur photographers handbook, by Aaron Sussman:
"Age, in combination with exposure to sun and air, frequently causes lenses to tarnish. When this occurs the surface acquires a perceptible discoloration, which has prompted some people to get rid of otherwise perfectly fine objectives(sic). Not too many years ago it was discovered that this tarnish actually improves a lens, makes it sharper and somewhat faster. Optical scientists learned that the tarnish reduces light reflection, allowing more light to pass through the lens than was the case before it had become tarnished. Experiments finally led to one of the most important advances in the science of optics in the last thirty-five years - artificial aging, or lens coating." page 77
How many uncoated lenses do you own? Perhaps you know better about 75 year old uncoated lenses than these folks.
My 1937 CZJ on M9 DNG right out of camera :
jena blue by unoh7, on Flickr
Perhaps you advise me to pull out some alcohol and clean this lens?
sevo
Fokutorendaburando
"Some", "counterintuitively" does not really suggest that can be generalized. It has never been stated what lenses he was testing there - in a lens factory, probably something returned as defective, or something that had gone through a weathering/ageing test. What he eventually patented was a hydrogen sulfide treatment.
Henry Scherer is a fine mechanic, but generally considered a unusually unsound source when it comes to theory.
Hard to tell, lenses seem to breed in drawers, as we discovered in a thread a few years ago. A dozen or two from the 19th century, another hundred or so from the 1900-1950 time frame (where some have what seem to be early coatings or after-market coatings). None appear to be bloomed.
uhoh7
Mentor
Unfortunately the term "bloom" is not helpful, since it can refer to the effect on some glass of prolonged exposure to the sun aka "surface oxidation", an applied coating, a fungus, haze, or a type of flare.
You imply the concept of natural lens coating or "surface oxidation" is a myth. Perhaps you should revise the wikipedia article on the history of photographic lens design to reflect this.
http://en.wikipedia.org/wiki/History_of_photographic_lens_design#Anti-reflection_coating
H. Dennis Taylor is simply lying or mistaken in his observations about older lenses transmitting more light? Reference to this by many authors just uninformed.
The idea older lenses were prized by photographers prior to the mass application of coatings, this is also a myth, or they were just ignorant?
The widespread acceptance of the phenonmenon of natural coating in astronomical circles is also mistaken?
And perhaps you have some example to back up your assertion that Henry is theoretically unsound? Or we should just trust a smug slur? After looking at literally thousands of CZJ samples, he is hallucinating when he comes across a sample with "surface oxidization"? Seems rather odd considering his level of experience.
You may be correct in all these views. But without a bit more evidence than "I can't find a single example", or "it's generally considered", it's baseless speculation all too common regarding any subject.
But if you can make a serious case I'm sure many would be interested in your findings, since so many would be shown to be mis-informed, myself included
In my case it would certainly not be the first time I had it wrong LOL
Meanwhile I stand by my advice be careful about any cleaning of this lens as it may degrade the optics.
another from my uncoated 1937 jena 50/1.5 which has never seen a drop of lens cleaner:
L1023014 by unoh7, f/9.5ish
DSC02414 by unoh7, on Flickr
tunalegs
Pretended Artist
I have only come across two naturally "bloomed" lenses in my collecting, both rather ancient. One in an Ansco Buster Brown box camera, and the other in an equally old Kodak Folder. So it can happen, but whether or not it improves anything I cannot say from experience.
goamules
Well-known
I had a 1940s Wollensak Velostigmat that had natural bloom. It was prior to their officially coating them.