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View Full Version : 90mm Raptar/Optar, f6.8, f/12.5--what's really the situation?



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

Carsten Wolff
13-Nov-2014, 20:07
I'm sure someone else will dig up the answer to this; all I thought I mention is that I've got a 159mm f12.5 Wide Angle Raptar, which of course has the disks: I widened them on a lathe and now its an f/6.8. Result: No discernible focus shift with improved ground-glass brightness. everything else seems the same, along with the nice 5x7" performance. The disks hold the groups in place, so discarding them doesn't work. Caution is advised; don't be tempted to widen them further as the cells will no longer be securely held in place. I looked at the 104/12.5 WA Raptar for this as well, but, from memory, couldn't alter the disk diameters for mechanical reasons, but I do think that they're largely the same design.

(An aside: I have a 108mm f6.8 now anyway, which seems nicer than the old 108mm f6.8 WF Dagor copy I once had; for color work in particular. I did a side-by-side against a 90mm f8 Nikkor-SW (yes, a somewhat different FL and not a fair comparison and I haven't got a SS110XL) Anyway, my WA Raptar copy holds its own at f22, even on 5x7").

Randy Moe
13-Nov-2014, 20:13
Hell if I know, but today I got a very clean Raptar 90mm f6.8 in Rapax shutter with bipost, which gleams bluish reflections front and rear, which I guess is coatings.

But you want an older one I think.

Adding, I want to keep mine.

mdarnton
13-Nov-2014, 20:19
Carsten, Yes, I have a 108/6.8 also. I am still kicking myself for not buying the matching 108/12.5 that went for around $60 a couple of weeks ago, to complete that set. I'll probably never get another chance. The 108 is a great lens for 4x5!

Randy, yup, that's another later one.

Randy Moe
13-Nov-2014, 20:34
And now I gotta look all this up.

This thing is sharp and does cover.

More research...

:)

Louis Pacilla
13-Nov-2014, 21:08
The Raptar Wide Angle 6.8's are 2 single elements w/ an air space in each cell so a double Gauss design with 8 air to glass surfaces & they covers around 85 degrees. Like the Wide Field Ektars

The Extreme Angle Raptar (coated) or Velostigmat IIIa f12.5 are a glued pair in each cell like a WAR design but w/ "newer glass" and only 4 air glass surfaces in this design so does well even w/out coating and has an angle of around 100 degrees

The Raptar Wide angle(coated) f9.5 or Velostigmat III design is 2 glued pairs w/ an air space between in each cell w/ better edge correction as the result of the extra elements in each cell & another 8 air to glass surfaces design. Because of the 8 air to glass surfaces this one really shines when it's the coated version.

mdarnton
13-Nov-2014, 21:20
The Raptar Wide Angle 6.8's are 2 single elements w/ an air space in each cell so a double Gauss design with 8 air to glass surfaces & they covers around 85 degrees. Like the Wide Field Ektars

The Extreme Angle Raptar (coated) or Velostigmat IIIa f12.5 are a glued pair in each cell like a WAR design but w/ "newer glass" and only 4 air glass surfaces in this design so does well even w/out coating and has an angle of around 100 degrees



Respectfully asking if you actually read and thought about what I wrote above before repeating what you already believed? What I have in front of me doesn't lay out as neatly as what you have said, in that my two Extreme wide angles are different from each other and therefore cannot be the same formula, that one of them is identical to the 90/6.8 and thus probably the same formula as the 6.8, and that and the three do not cover different angles --the 12.5s do NOT cover more than the 6.8. So basically, what you said is not the correct story.

What I'm asking is that people stop repeating the same old myths, take a look at the actual lenses and see what they are and what they do.

For instance, if the 12.5 covers 100 degrees, that's about 214mm if I have calculated correctly--quite a bit more than 5x7. Which it most certainly is not doing here: https://www.flickr.com/photos/rabato/13089416563/ This duplicates my experience with the lens, as well.

Liquid Artist
14-Nov-2014, 01:43
That kinda looks like my 90mm f6.8 did when I used a filter in the front on a 4x5.
Since I ditched the series filter holder altogether I haven't had any real issues. I haven't tried it on my 5x7 yet, but would assume it doesn't cover.

mdarnton
14-Nov-2014, 06:29
I do notice that mine don't gradually fade off at the edges as some lenses do at the fringes of coverage. These go black all at once: thud>nothing. That's without a filter ring. That front ring is pretty small, and you can see the serrated edge when looking through from the back of the lens. If I had a real junker lens, it would be interesting to start grinding the outside ring back to see if coverage increased. :-)

Liquid Artist
14-Nov-2014, 17:17
I thought I read somewhere that rotating backs can cause similar effects with wide angle lenses.
Although I don't know why, and I have never seen it quite to that extreme.

Tim Meisburger
14-Nov-2014, 17:34
Your theory about the mechanical vignetting is interesting. I have had a lot of trouble with vignetting on my 90mm Optar when using filters held in by an old Series lens hood, and have thought about grinding one down to eliminate the problem. It would be really interesting if the lens housing itself was causing vignetting.

Ramiro Elena
15-Nov-2014, 16:36
Michael, I have to say I haven't tested my 90 EXWA further and I believe/suspect the vignetting is mechanical. It could well be my handmade lens board. I should do more tests.