7x17 coverage

[ronald lamarsh]

I am considering building a 7x17 rear standard for my 5x7. I've read that one should use a lens that is appropriate for the 5x7 format(210mm240mm) to maintain the panoramic qualities of the format. So what lenses does everyone out there use that have that kind of coverage?

[Ernest Purdum]

If I did the math right, you need something over 467mm coverage. This means a lens suitable for the 11" X 14" fomat. The Schneider Super-Angulon 210mm f8 and the Rodenstock 200mm f6.8 Grsandagon-N are two possibilities. I hope your 5" X 7" camera has a sturdy front standard. These are big and heavy lenses.

[sanking]

There are really very few good choices in the 210mm to 240mm range for the 7X17, at least not in the area of bargains. Ernest is right in that you need a lens that will cover a circle of about 467mm.

Here are some of your choices, and the negatives.

1. The 210mm Super Angulon and 200mm Grandagon-N will certainly cover but they are really huge. I used the big Super Angulon on my 7X17 for a couple of years but eventually got rid of it because it was just too big for my style.

2. The new 210mm Schneider SSXL is slightly smaller than the 210 Super Angulon, but is not cheap. Good choice if money is no object but stll very big.

3. 210 f/6.8 Schneider Angulon. This lens is small and has a circle of illumination that covers the 7X17 format easily, but it is very soft at the corners, even when stopped down to f/32 or f/45. Overrated and overpriced in IMO.

4. 183 f/18 Series V Protar. Very small lens and some specimens will *just* cover the 7X17 format. Mine vignettes every so slightly.

5. 210mm f/9 Computar. Very small lens with huge coverage and will cover the format sharply all the way to the corners. This would be my first choice in this focal length for a really wide-angle lens for the 7X17 because of the combination of coverage and small size. But very hard to find!! I have a 300mm version of this lens and it covers 12X20 with about three inches of movement.

5. 240mm Goerz Dagor will cover 7X17 but the corners will be very soft. A better lens would be the Zeiss Dagor of the same focal length, but these are hard to find. Offers a good compromise of performance and price while still being fairly wide ange.

6. 270mm Goerz Dagor. This lens would cover 7X17 nicely, allowing a bit of movement, and is still very wide for the format.

[tim atherton]

"5. 210mm f/9 Computar. Very small lens with huge coverage and will cover the format sharply all the way to the corners. This would be my first choice in this focal length for a really wide-angle lens for the 7X17 because of the combination of coverage and small size. But very hard to find!! I have a 300mm version of this lens and it covers 12X20 with about three inches of movement."

Sandy,

this would be the same as the Kowa/Kyvytar 210 f9/6.8 I think (there was one just on ebay).

Have you actually tried it? @f22 some say it covers 460mm, but that seems over optimistic imo based on the Kowa. I'd say around 380mm @f22. I think Jim Galli may have tested the Computar.

It may cover that at around f45?

tim

[Michael Jones]

Sorry Tim, the f6.8 is not the same construction as the f9 Kowas. It has about the same coverage as any other plasmat, maybe 250mm of coverage on a good day.

Mike

[Jim Galli]

Michael, I think you're confusing the 6.3 Symmetrigon with the 6.8 lens. The f9 Computar is limited by the barrel mount. There's actually f6.8 available when mounted in Copal 1 shutter. When Kyvyx inherited and sold them they changed the wording on the front and it actually says f6.8. I've got both; a f6.8 Kyvytar and an f9 Computar and also an f9 Graphic Kowa and the parts are interchangeable. That said though i couldn't get more than about 380mm circle out of any of them. 10X12 maybe but not 1114. So maybe there are some differences I don't know about.

To answer the original question though, a 305 G-Claron is a great choice and so is the Konica 260mm GRII. (Won't go in a shutter) I just got a Graphic Kowa 240 f9 and it looks promising but doesn't go in a shutter easily. All of these are relatively light and inexpensive and excellent for sharpness.

[tim atherton]

Mike my Kowa 210 f9 actually opens to 6.8 now it's in a shutter, and does give me about 380mm coverage @f22

[Michael Jones]

I agree, I thought Tim was referring to the Symmetrigon. My confusion rests with the atual marking on the lens. Sorry.

Mike

[sanking]

The 210mm Computar Symmetrigon, which I think is a f/6.8 lens, is not the one that covers 7X17.

I don't know the history of the 210mm f/9 Computar but there may have been more than one design marketed under this name and aperture. In any event the 210mm f/9 Computar I mentioned in the first post is definitely not the same lens as 210mm Kowa Graphic. The 210 Kowa Graphic does not come even close to covering 7X17.

[tim atherton]

Sandy,

any idea if this is the type of Computar you are referring to?:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2950592709&category=30076

I'm interested if you have measured the iamge circle on one so we can get some actual figures?

thanks

tim

[sanking]

Tim,

The lens that sold on Ebay appears to have similar marking to my 300mm Computar that easily covers 12X20. My 300mm F/9 Computar has an image circle of almost 700mm, all of it useful for contact printing when stopped down to f/45 or more.

I do not have a 210mm f/9 Computar but from past reports of people who use this lens on 7X17 I understand that it covers the format and allows just a tad movement. If coverage is similar to my 300mm lens the circcle of illumination would be around 480-90mmn, and that seems consistent with what I have been told.

[tim atherton]

Interesting Sandy - just going by the photo's, the one on ebay looks identical to my Kowa, and Jim has found the Kowa/Kyvytar/Computar 210's to be basically identical, and most of the reports I've seen appear to say they are basically the same lens (though it wouldn't suprise me if they did make different versions - especially for diferent process camera set-ups/photocopiers etc).

But I note you are talking about coverage at f45. My 210 covers about 380mm @ f22. I'll have to figure out what it actually covers @f45 - maybe closer to the 460/480mm I've seen mentioned. All I can say is that f45 I haven't run out of space with my Phillips 8x10 (or Deardorff before that).

Jim - when you tested it on the 11x14, was it @f22?

tim

[sanking]

Tim,

The circle of illumination for most lenses does not increase very much,if at all, as you stop down. What increases with most lenses as you stop down is the circle of good definition. For example, the circle of illumination of my 300mm Computar is slightly less than 700mm at f/9, and virtually the same at f/45. However, at f/9 the image is too soft at the corners even for contact printing, but as you stop down the sharpness improves greatly so that by f/45 the image is good enought for contact printing from corner to corner, i.e. the circle of illumination for my purposes is same as the circle of good definition.

[Michael Mutmansky]

Tim,

I have heard it from other people there the Kowa and Computar are definately not the same lens...

Apparently, there is some variation in the specs, but we'll never know what these variations are. The person that I talked to mentioned that he had both a Kowa and a Computar 210, and the Kowa, while it looked similar, had a different curvature to the rear element, at least.

So, the differences may be very subtle. From the information I have been told, the Kowas have a smaller IC, then come the Computars, and I don't know where the Kyvytars fit into this, although I suspect they have at least comparable IC's to the Computars.

It's important to remember that for 7x17 or other banquet formats, f22 is not really an option for these lenses, or really any lens, because of field curvature and other lens quality issues that rear their ugly heads.

I have shot at f22 in the past with some longer lenses with the 7x17, but I am more often in the f32-f45-f64 realm. Don't worry, diffraction is present, but inconsequential when you are contact printing. It's much more important to have the corners sharp and properly exposed, and stopping down the lens helps with both regards.

I want to add that a 240 Kowa/Computar/Kyvytar might be an excellent lens for 7x17. It has a good bit larger IC than the 210, wich results in better performance and a bit easier time making sharp images.

I have a 240 Kyvytar fitted in a 3S shutter (the 210 is the longest in the #1 shutter). It does come native in a 3S, but, like the Computar and Kowas, there are somesamples out there that were designed for specific copy cameras, and do not fit into Copal shutters. The kyvytar is about 1" short of covering 12x20 at infinity, so there is plenty of room for 7x17.

I also have a Computar 210, and it does cover 7x17 when stopped down. It does prefer to be focused at a hyperfocal point, to help with the corner sharpness.

I do use the Computar sometimes on 7x17, but I think it makes an excellent 8x10 lens, with all the coverage you could ask for. The 240 is a better 7x17 lens, because the 210 just doesn't have any extra for movements. I figure that if I'm going to lug a banquet camera out in the field, I'd better have the ability to correct for convergence, etc. I don't like using it like a big P+S, which is what a view camera is reduced to if you don't have room for movements.

---Michael

[Jim Galli]

Tim, yes, f22. My Computar looks like the one that just sold on Ebay and I haven't tested it on big stuff yet, it was the Kowa I tried at f22 on the 1114. I'll give the Computar f9 a testing and see what if anything it does differently. This is getting interesting. Jim

[tim atherton]

Jim,

it would be intersting to test the Kowa at f45 too to see if there is a difference?

(BTW - Jim and I are working on a plan to corner the world supply of Kowa's and Computars and then get Kerry to write a glowing article on them in View Camera... :-) )

[tim atherton]

Sandy, I get lost on the nuances of lens design, but I was under th impression that the Kowa/Kyvytar?cumputar f9/6.8's were similar in design to the G-Clarons (and also the f9 Dagors?) in that the effective circle of illumination (? starts to get confused with terms here....) does increase substantially as you stop down.

tim

[tim atherton]

that should be - Kowa/Kyvytar/Computar f9/6.8's

[tim atherton]

"The 210mm Computar Symmetrigon, which I think is a f/6.8 lens, is not the one that covers 7X17."

Just a note - the Computar Symmetrigon's are 6.3 lenses and a different design.

The Apo-Kyvytar/Kowa f9's are actually f6.8 when mounted in a shutter (as the Computar may also be...?)

Which, of course, is a great help for focussing.

I know some of the Kyvytars were factory mounted in shutters and labelled 6.8 - I'm not sure if any Kowa's were ever factory mounted in shutters? Or only ever came as barrel lenses.

tim

[sanking]

Tim,

The circle of illumination is the largest circle the lens will project at a given magnification.This circle of illumination does not increase on stepping down, and if so, it is only by a very small amount. This is true of virtually all lenses, including Dagors, Symmars, Computars, Tessars, etc.

With many lenses, and I will include here Dagors, Kowa Graphic, Computars, the image at the far edges of the field of the circle of illumination will be unacceptably soft. As you stop down the aberrations of the lens are eliminated or cancelled and the result is that the image performance at the corners improves considerably. Whatever becomes acceptable to you becomes the circle of good definition. For contact printing that figure is generally considered the ability to resovle 5-10 lpm on the film.

Many people appear to believe that stopping down actually increases the size of the circle of illumination. That is not true with the vast majority of designs.

Generally speaking we could group lenses in three broad categories as regards the circle of illumination.

1. Lenses that have a very large circle of illumination that improves at the corners on stopping down. (Dagors, Protars, G-Claron, Kowa Grapic, Computar, Symmars)

2. Lenses that have a very large circle of illumination that will not become acceptably sharp on the corners of the field no matter how much you stop down. The Apo-Nikkor is a good example of this type of lenses. A 420mm Apo-Nikkor has a circle of illumination that covers the 12X20 format at infinity, but no matter how much you stop down this lens will not have acceptable performance on the corners.

3. Lenses that are mehcanically vignetted so that the circle of illumination is the same, or close to, the circle of good defninition. Most moderns lenses are mechanically vignetted to some extent, and some of the odler ones are as well. The reason is because the extra light can cause flare.

[tim atherton]

that's where I start to get lost in the math and physics Sandy (along with the confusion of common usage...)

tim