mdarnton
13-Nov-2014, 19:37
Another thread prompted me to do something I've been intending to do, and I'd appreciate some others' input on what I am seeing. The implied question was about the difference between 90/6.8 lenses and 90/12.5 lenses from Wollensak. I'm a bit habituated to these guys, having bought three of them, and read everything I could find about them.
The question is whether the 12.5 version is different from the 6.8, or whether it's merely the same lens stopped at 12.5. The evidence to be considered includes that the 12.5 diaphragm has a stop on it that when removed turns it into a ~6.8 lens. The implication in Wollensak's advertising is that the 6.8 version covers 4x5, nothing more, but that all of the 12.5 lenses of various focal lengths cover upwards one film size. A peculiarity of that is that if one reads Wollensak's advertising carefully, the step up to the next size alternates between sizing systems: the 5x7 12.5 lens covers not 8x10, but 6.5x8.5. The 90mm 12.5 does NOT cover 5x7, and Wollensak never claims that. It would, it appears, cover half-plate, 4-1/4x6-1/4, but that size doesn't appear to exist for Wollensak in their materials, so it's unclear what they intended it to cover. They actually only ever claim 4x5, though those who are selling them usually say 5x7. Pictures from Ramiro Elena's 90/12.5 examples clearly show that 5x7 is not covered, as does my experience, also.
Add to that the fact that this lens of supposedly superior covering power was usually mounted in the inferior Alpax shutter, and sold for less than the 6.8 lens, which implies an attitude from Wollensak about the lens' place in their lineup.
The hidden implication in all of this is that the 12.5 lens is simply the 6.8 lens sold in a cheaper shutter, which gains it's justification for existence from having better coverage, which isn't real coverage, being what the 6.8 always does anyway when it's stopped down, and that Wollensak was able to sell it as a larger-coverage lens simply by preventing the use of stops where it covered less.
In the recent thread is was alleged that the 12.5 lens is a different lens, not the same lens, and I thought I would try to definitively figure this out without tearing my three lenses to pieces, so I decided to take them off their boards, give them a good hard external examination, and try to figure out whether they were different or the same.
Here's what I have: a very late and coated 90/6.8 Optar, a late and coated 90/12.5 Extreme WA Raptar, both in black Rapax (or the identical Graflex) Synchro shutters, and an earlier uncoated 90/12.5 ExWA Raptar, in the very simple Alphax.
Here's what I found:
Coverage at f32, determined by putting the three lenses in a row on a light table and decreasing my angle of view while watching the f32 close down into nothingness: exactly the same. Thus, no reason at all to buy one lens over the other, if basing the decision on coverage.
More interesting was the physical aspects of the lenses, and that was that the two later lenses have exactly the same glass diameters, front and back, being more or less equal. And that the reflections in those two lenses, both front and back, are more or less equal: two reflections, pretty much the same size. However, the early uncoated 90/12.5/Alphax lens has a front element a couple of mm larger than the later lenses, and a back that's a couple of mm smaller. The reflections are different, too--the two reflections, front and back, are different sizes.
The conclusion I draw from this is that the two later lenses are the same formula, one of them throttled, and the earlier lens is a different formula. What I'm missing is an earlier, uncoated 90/6.8, to answer two questions: on that lens would the front and back elements be different sizes, and would the internal reflections be different sizes, to match my early 90/12.5 (then implying that the 12.5 and 6.8 lenses have never been different from each other, and changed together when modernized), or would all of those be equal, matching my later lenses, in which case the early 12.5 lens is a different formula, whereas the later one is not.
Simplified question, then: was the 12.5 lens every actually a different lens and formula from its contemporary 6.8 lens, or not? It appears at the end it was definitively the same lens, one crudely throttled to give the appearance of wider coverage. What about the uncoated 90/6.8, which I don't have, against my uncoated 90/12.5? Was it that same as the more modern 90/6.8 and 12.5, or was it the same as the earlier 90/12.5, or was it something else, again?
To those who think this to too much micro-thinking, my apologies.
Those who choose to disagree with me are welcome to submit their actual evidence, not their unsupported lore and collected myth, of which there is WAY WAY too much on the web on this topic.
The contestants:
https://lh3.googleusercontent.com/-Rf4I7SMVk-g/VGU5mLOJHTI/AAAAAAAACvM/QHHgXmqpmv4/w743-h557-no/20141113_170437.jpg
https://lh6.googleusercontent.com/-EIuFicz7wpE/VGU5EA2IJMI/AAAAAAAACuo/Kzdx1Dw5rTg/w743-h557-no/20141113_170420.jpg
The question is whether the 12.5 version is different from the 6.8, or whether it's merely the same lens stopped at 12.5. The evidence to be considered includes that the 12.5 diaphragm has a stop on it that when removed turns it into a ~6.8 lens. The implication in Wollensak's advertising is that the 6.8 version covers 4x5, nothing more, but that all of the 12.5 lenses of various focal lengths cover upwards one film size. A peculiarity of that is that if one reads Wollensak's advertising carefully, the step up to the next size alternates between sizing systems: the 5x7 12.5 lens covers not 8x10, but 6.5x8.5. The 90mm 12.5 does NOT cover 5x7, and Wollensak never claims that. It would, it appears, cover half-plate, 4-1/4x6-1/4, but that size doesn't appear to exist for Wollensak in their materials, so it's unclear what they intended it to cover. They actually only ever claim 4x5, though those who are selling them usually say 5x7. Pictures from Ramiro Elena's 90/12.5 examples clearly show that 5x7 is not covered, as does my experience, also.
Add to that the fact that this lens of supposedly superior covering power was usually mounted in the inferior Alpax shutter, and sold for less than the 6.8 lens, which implies an attitude from Wollensak about the lens' place in their lineup.
The hidden implication in all of this is that the 12.5 lens is simply the 6.8 lens sold in a cheaper shutter, which gains it's justification for existence from having better coverage, which isn't real coverage, being what the 6.8 always does anyway when it's stopped down, and that Wollensak was able to sell it as a larger-coverage lens simply by preventing the use of stops where it covered less.
In the recent thread is was alleged that the 12.5 lens is a different lens, not the same lens, and I thought I would try to definitively figure this out without tearing my three lenses to pieces, so I decided to take them off their boards, give them a good hard external examination, and try to figure out whether they were different or the same.
Here's what I have: a very late and coated 90/6.8 Optar, a late and coated 90/12.5 Extreme WA Raptar, both in black Rapax (or the identical Graflex) Synchro shutters, and an earlier uncoated 90/12.5 ExWA Raptar, in the very simple Alphax.
Here's what I found:
Coverage at f32, determined by putting the three lenses in a row on a light table and decreasing my angle of view while watching the f32 close down into nothingness: exactly the same. Thus, no reason at all to buy one lens over the other, if basing the decision on coverage.
More interesting was the physical aspects of the lenses, and that was that the two later lenses have exactly the same glass diameters, front and back, being more or less equal. And that the reflections in those two lenses, both front and back, are more or less equal: two reflections, pretty much the same size. However, the early uncoated 90/12.5/Alphax lens has a front element a couple of mm larger than the later lenses, and a back that's a couple of mm smaller. The reflections are different, too--the two reflections, front and back, are different sizes.
The conclusion I draw from this is that the two later lenses are the same formula, one of them throttled, and the earlier lens is a different formula. What I'm missing is an earlier, uncoated 90/6.8, to answer two questions: on that lens would the front and back elements be different sizes, and would the internal reflections be different sizes, to match my early 90/12.5 (then implying that the 12.5 and 6.8 lenses have never been different from each other, and changed together when modernized), or would all of those be equal, matching my later lenses, in which case the early 12.5 lens is a different formula, whereas the later one is not.
Simplified question, then: was the 12.5 lens every actually a different lens and formula from its contemporary 6.8 lens, or not? It appears at the end it was definitively the same lens, one crudely throttled to give the appearance of wider coverage. What about the uncoated 90/6.8, which I don't have, against my uncoated 90/12.5? Was it that same as the more modern 90/6.8 and 12.5, or was it the same as the earlier 90/12.5, or was it something else, again?
To those who think this to too much micro-thinking, my apologies.
Those who choose to disagree with me are welcome to submit their actual evidence, not their unsupported lore and collected myth, of which there is WAY WAY too much on the web on this topic.
The contestants:
https://lh3.googleusercontent.com/-Rf4I7SMVk-g/VGU5mLOJHTI/AAAAAAAACvM/QHHgXmqpmv4/w743-h557-no/20141113_170437.jpg
https://lh6.googleusercontent.com/-EIuFicz7wpE/VGU5EA2IJMI/AAAAAAAACuo/Kzdx1Dw5rTg/w743-h557-no/20141113_170420.jpg