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View Full Version : 270mm Computar covers 12X20?



sanking
30-Mar-2005, 15:02
Quite some time ago I reported on some testing of Computar lenses for ULF work. If interested the thread is at http://largeformatphotography.info/lfforum/topic/498719.html

At that time I did not have a 270mm Computar to test but I speculated that if its coverage were equal to that of the 210mm, 240mm and 305mm Computars it should cover, or come very close to covering, 12X20. A few months ago I acquired a 270mm Computar, but for various reasons I was unable to actually test the lens until just a few days ago. I am pleased to report that the circle of illumination of this lens does indeed cover 12X20", with just a bit of movement. Of course, in order to get decent performance on the corners you will need to stop down to f/45 or f/64, but that is not such a big deal since we generally do this anyway with 12X20 format.

Many people want to know if the Kowa Graphic is the same lens as the Computar. There does not appear to be a definitive answer to this question. I have tested a couple of Kowa Graphics, both 240mm, that had the same coverage as the 240mm Computar. However, so far I have not seen a Kowa Graphic in 210mm, 270mm and 305mm with as much coverage as the Computars of this focal length.

Alan Barton
30-Mar-2005, 15:52
Is this the same lens that is mentioned (but name not divulged) on the Glennview site?

sanking
30-Mar-2005, 16:10
"Is this the same lens that is mentioned (but name not divulged) on the Glennview site?"

I suspect it is the same lens, but obviously don't know for sure.

Tom Keenan
30-Mar-2005, 18:01
I actually bought one of those mystery 210mm ~f8 lenses from the glennview site a few months ago. Turned out to be Computar 210mm/f9. Nice lens in a Copal 1 shutter. I'm sure I paid too much.
TK

Tracy Storer
30-Mar-2005, 18:40
I have a 270mm Graphic-Kowa. I checked mine ages ago at f/22 and found it to throw about a 19" circle. 11x14, but not 12x20. There were different variations at least in the mounting of these lenses. The rear cell of my 270, for example, is integral to the barrel, and the front cells threads don't fit a #3 or #3S shutter. (at least I got it cheap)

sanking
30-Mar-2005, 19:11
"I actually bought one of those mystery 210mm ~f8 lenses from the glennview site a few months ago. Turned out to be Computar 210mm/f9. Nice lens in a Copal 1 shutter. I'm sure I paid too much."

You could have paid less, that is for sure. But on the other hand, the 210mm f/9 Computar is a fabulous lens. You have a lens about the size of a quarter in a #1 Copal that covers 11X14, and *just* or *almost* 7X17. And it is a modern coated optic.

To put this in perspective, the coverage of the Computar is about 95 degrees, more or less on a par with the Series IV Protar. What would one expect to pay for a 210 mm coated Series IV Protar in a Copal #1 shutter?

I hope that discussions of this this type will make the qualities of the Computars better known to more ULF photographers because, ounce for ounce these lenses are, IMO, simply extraordinary for this application.

Kerry L. Thalmann
30-Mar-2005, 19:38
I actually bought one of those mystery 210mm ~f8 lenses from the glennview site a few months ago. Turned out to be Computar 210mm/f9. Nice lens in a Copal 1 shutter. I'm sure I paid too much.

I see he also now has a ~300mm ~f8 "mystery lens" for $3300 listed on his web site. Given the fact that we now now the 210mm mystery lens is a Computar, it's probably safe to assume this new "mystery lens" is a 305mm f9 Computar (geez, and to think I sold mine in a Copal 3S shutter for $500 a few years back - I also sold my 210mm f9 Computar for $325 - wish I still had that one).

It's probably also not a coincidence that is his "wanted" section he's looking for: 305mm F9 Computar lens and other F9 Computar lenses. He's also looking for: Rear element group for 210mm F9 Computar. A whole lens will do. and Apo-Kyvvtar F9 view camera lenses.

A couple other interesting tidbits from the glennview.com web site. He is currently offering a 165mm f9 Computar that consists of a210mm Computar front cell and a 150mm Computar rear cell (guess we know why he's looking for that 210mm Computar rear element group). Has anyone tried combining different cells from various Computar lenses? If so, how was the performance? I know the APO Kyvytars were sold as convertibles, but to convert these lenses you simply remove the front cell and use the rear cell alone behind the shutter (just like the convertible Symmars).

It is also interesting that his prices for Graphic-Kowa lenses are a LOT less than the Computars (and no "mystery" surrounding them). He also mentions combining various cells in his listings for the 305mm and 360mm Graphic-Kowas. He claims that you can use any combination of cells that screw into the same shutter. Sandy, as you seem to own several Computars of various focal lengths, could you give this a try sometime and let us know how it works out?

Kerry

sanking
30-Mar-2005, 20:34
"I know the APO Kyvytars were sold as convertibles, but to convert these lenses you simply remove the front cell and use the rear cell alone behind the shutter (just like the convertible Symmars). "

"He claims that you can use any combination of cells that screw into the same shutter. Sandy, as you seem to own several Computars of various focal lengths, could you give this a try sometime and let us know how it works out? "

Kerry,

I think he is right. I now have four Computars, 210mm, 240mm, 270mm and 305mm. The 210mm goes into a Copal #1 and the elements can not be interchanged with the other three lenses. The 240mm, 270mm and 305mm Computars all screw directly into a Copal #3S shutter.

What I have determined is this. 1) the Computar is a symmetrical plasmat design that can be used as a convertible lens by removing the front element, with the rear element giving about 1.75X the focal length of the combined lens and, 2) elements from the 240mm, 270mm and 305mm Computars can be interchanged in various combinations to give a rather wide range of focal lengths.

I suspect, but don't know for sure, that APO Kyvytars are same as Computars, the only exception being that they were marketed as convertible lenses whereas the Computars were not. Most likely because during the period when Computars were introduced, in the 70s, convertible lenses had fallen out of favor. This was, at last in part IMO, a resuslt of the replacemnt of the old convertible Symmar with the non-convertible Symmar-S.

In any event the Computar is as good with the single element, if not better, than the convertible Symmar. In fact, its useful circle of illumination appears to be quite a bit larger.

Kerry L. Thalmann
1-Apr-2005, 00:06
Sandy,

Sorry to hijack your thread...

When it comes to lens selection, I'm at the opposite end of the spectrum. I have one of each type (Computar, APO-Kyvytar, and Graphic-Kowa) in the 150mm focal length, and a 210mm Graphic-Kowa. The APO-Kyvytar is in its original factory supplied shutter with dual aperture scales (150mm f6.8 combined and 264mm f13.6 for the rear element alone). I just got back from a trip where I shot 4x10 with both the 150mm and 210mm Graphic-Kowas, but the film hasn't been processed yet.

The goal is to eventually shoot all three 150s (along with a 150mm Germinar-W, 150mm G Claron, 150mm APO Sironar (-W), 150mm Super Symmar HM and 159mm Wollensak Ext. WA) on 8x10. In theory, all these lens will cover 5x7, but only the Wollensak (and perhaps the Computar) will cover 8x10. I'm real curious to see how the coverage of the Computar, APO-Kyvytar and Graphic-Kowa compare to each other. However, I'm in the middle of a couple other projects/articles that have rapidly approaching deadlines. So, it will be a while before I get around to completing this one.

While I'm at it, I'll probably test the coverage of the 210mm Graphic-Kowa, and I'll also try combining cells from the 150mm and 210mm Graphic-Kowas to see how that works as well.

Kerry

michael boruch
16-Aug-2005, 22:10
Hi.

I acquired two graphic-kowas, a 150 and a 210, from a retired vertical copy camera. Have been using them as taking lenses. The 210 does a nice job on 8x10. The 150 'walker evans' the corners a bit.

Because these were designed as process lenses, their optimalization are probably near 1:1.
My guess is that, like the artars, the optimalization can be modified by changing the separation between the front and back groups. Short of looking at the aerial image w/o the ground glass but with high power eyepiece and / or taking numerous test shots, do any of you know any 'rules of thumb' on how the group separation might effect optimalization?

mike boruch

John Z.
17-Aug-2005, 10:13
This information has been very helpful--thank you all. My understanding from what I have read here and elsewhere is that the 210 Computar may barely cover 11x14, but the 240 will cover with movements (but the Kowa may not). Based on this info I will look for a 240 Computar now for my 11x14 camera.
Now if I can just figure out where to find one.... Thanks,

John

Jerry Xu
2-Feb-2006, 07:13
The goal is to eventually shoot all three 150s (along with a 150mm Germinar-W, 150mm G Claron, 150mm APO Sironar (-W), 150mm Super Symmar HM and 159mm Wollensak Ext. WA) on 8x10. In theory, all these lens will cover 5x7, but only the Wollensak (and perhaps the Computar) will cover 8x10. I'm real curious to see how the coverage of the Computar, APO-Kyvytar and Graphic-Kowa compare to each other. However, I'm in the middle of a couple other projects/articles that have rapidly approaching deadlines. So, it will be a while before I get around to completing this one.

Kerry,
Have you had a chance to do the comparision? It is particlularly interesting on the Kyvytar since there are rumors that this is the same lens as the Computar. I have a 210mm APO-Kyvytar which is different from the 210mm Computar and versions of Kowa Graphic. The glass on the Kyvytar IS bigger by a small margin. The curve of the glass is flatter also. But I don't have a 150mm Kyvytar and wouldn't know if it is the same as the Computar/Kowa Graphic or whether it will cover 8x10. My 150mm Computar just missed the coners of 8x10.
Jerry