The Computar lens and ULF coverage.

[tim atherton]

Okay - here's the other bit I snipped (first post didn't seem to make it) - again, I'm not sure if this was actually talking about the Computars or Kowas (though apparently both were made by Kowa?)

"Some times the barrel lens will come with thin spacers. The trick is this, for center image use, the more spacers between the rear cell and the shutter the better. For the corners of the image, no spacer is best. This is why, in a shutter mount, we often see one spacer as the best overall compromise."

[tim atherton]

Kerry, I've read the Kowa 150mm is supposed to cover about 290mm? (what's the circle for 4x10?)

Also, the APO-KYVYTAR's where apparently made in 150mm - don't think I've seen a reference to a Computar 150mm.

BTW Sandy, I've bid on a couple of Computar 210's on ebay in the last six months (more out of curiosity to compare with the Kowa). I didn't win, but neither went for more than $420.00... Also, one was obviously an original factory shutter mount with the dual/convertable aperture scale.

[tim atherton]

"The Germinar-W series is very interesting"

Kerry, did they ever make a 190mm f9?

[tim atherton]

Here you go Sandy (I've got these scattered through different emails that I use to "clip" notes into...) - again, I can't remeber where I clipped it from - might have baan an ebay sale....

"The following is from the beat up information sheet, (a letter) which was packaged with my 305/537 APO-Kyvytar and in the box with the Korona.

It is not dated.

"APO-KYVYTAR lenses are made by the same people in Japan that made the convertibles under the "Computar" trademark which I used to own and which I sold to Chugai International Corporation who use the trademark for their video lenses, enlarging lenses, and the large format taking lenses (Computar Symmetrigons).

The APO-KYVYTARs are the same formula as the former Computar convertibles except that the APO-KYVYTARs are one stop faster, i.e., 6.8 instead of 9.0

The APO-KYVYTARs convert to a focal length just a little less than double the nominal focal length simply by un-screwing the front element and using the rear element.

The APO-KYVYTARs convert in focal length as follows:

>From 150mm to 264mm 210 370 240 422 270 475 305 537 360 633 480 845

The diaphragm scale is a double scale. The second scale is for use with the single rear element. The rear element alone is slightly softer and therefore good for portraits where it is desirable to shoot farther from the subject and soften the texture of the subjects faces.

Both elements together give you the sharpest picture, and flattest field, and the best color that money can buy!"

It is signed by J. Callahan, President, KYVYX Corporation, South Hackensack, NJ."

I've tried my 210 as a 370mm - it' actually pretty nice. But I have only really used it for close-ups of flowers, so the background i all out of fiocus anyway - so not really a scientific test. That said, as a 210mm lens, it's a sharp snappy little bugger

BTW - the Kowa's also become 6.8 once you put them in a shutter (I think Jim Galli forked out for a WA Kowa 6.8 only to find it was exactly the same as his barrel f9 he had, only difference was it was already mounted in a shutter...?)

[tim atherton]

lets try this:

150mm to 264mm

210 370

240 422

270 475

305 537

360 633

480 845

[sanking]

Tim, Kerry

Wow, thanks for all of the additional information. This has turned into one of those ask and yee shall receive threads.

Kerry, do you have a list of the focal length in which the Germinar-W was made?

Tim, the information about the spacers is very useful. This is just a rough estimate but I am guessing that by not using the spacers when I put the 210 Computar in a shutter the elements will be about 0.12" closer, which should result in an increase in coverage of some 10-15mm. If that is indeed the case it will hit all of the corners on 7X17, with just a tad to spare.

[Kerry L. Thalmann]

Kerry, I've read the Kowa 150mm is supposed to cover about 290mm? (what's the circle for 4x10?)

Allowing for film holder margins, about 266mm.

The 290mm figure, as well as 460mm for the 210mm focal length are from an article Gordon Hutchings did many years ago for View Camera. I believe that article is also the source of your quote above about Burleigh-Brooks and the lineage of the Computar/Kowa/Kyvytar lenses.

What's confusing about the numbers is the inconsistancy of the stated coverage. A 460mm image circle from a 210mm lens equates to 95 degrees of coverage (in line with Sandy's data for his Computars). With 95 degrees of coverage, the 150mm focal length should have an image circle of about 327mm, not 290mm. So, why does the 150mm cover so much less (if in fact it does). As both lenses are designed to fit in a Copal No. 1 shutter and both take the same size filters, I would not suspect mechanical vignetting to limit the 150mm coverage so significantly. The other possibility is the 290mm figure was for a 150mm Graphic-Kowa, and the 460mm spec was for a Computar. I have no idea of this is true, but it falls in line with Sandy's conclusion that these are indeed two different designs with the Computar having the greater coverage.

Kerry

[Kerry L. Thalmann]

Kerry, did they ever make a 190mm f9?

No, they jumped right from 150mm to 210mm.

Kerry

[sanking]

Kerry,

One more comment about the Graphic Kowas. The experience of others may be different but mine is that they do not quite hit 80 degrees of coverage. I tried several different 360mm specimens on 12X20 and they all missed the corners. My calculations are that a 360mm lens would cover 12X20 if it had a full 79 degrees of coverage so the fact that the Kowas did not puts the ones I sampled below that figure.

But maybe the ones of shorter focal length do go 80 degrees or more. It is not uncommon for lens manufacturers to reduce coverage on the longer focal length lenses. I believe this was true of the Fujinon-W, for example. I have a 180mm f/5.6 Fujinon-W that covers more than 80 degrees, but a 360mm F/6.3 I owned missed the corners on 12X20, which puts it below 79 degrees.

[sanking]

"The 290mm figure, as well as 460mm for the 210mm focal length are from an article Gordon Hutchings did many years ago for View Camera. I believe that article is also the source of your quote above about Burleigh-Brooks and the lineage of the Computar/Kowa/Kyvytar lenses."

Anyone have the year and month of this article?