Question on Convertible lenses

I'm planning to get a Schneider convertible lens. I own a field camera

with ~32cm maximum extension bellows. I'd like to have a Symmar 240mm

that can convert to 420mm... Question is: by removing the rear element

instead of the front element as suggest by Schneider, will I be able

to use the "converted" 420mm on my camera?

 

Are there other manufacturers that make convertible lenses other than

Schneider?

 

thanks

I remember using a Cooke ,triple convertible years ago.You have 3 different focal lengths depending on which element you change,I remeber it was a pretty sharp lens, although a little slow.

No it will not work!

I have the 210mm Symmar convertible and if I remember correct I need for the right conversion 370mm only the behind the shutter one and with the front about 420mm.

Will not work!

"Are there other manufacturers that make convertible lenses other than Schneider?"

 

The Schneider convertible you're planning to buy was last made in 1972. Neither Schneider nor any other company that I know of currently makes convertible lenses except the triple convertible that Cooke recently introduced, which is a modern version of its old Series XV triple convertible. Unfortunately it costs several thousand dollars, I forget the exact price because whatever it was I knew I'd never pay it. In the old days convertibles were common and many companies besides Schneider made them. Turner-Reich, Cooke, and Wollensak come to mind, I know there were others but those are the ones that come to mind. At one time I owned a Wollensak 330, 510, 620 (approximate numbers)triple convertible. At its 330 length it was a very good lens for 8x10, at its converted lengths it was so-so - better than losing the picture entirely for lack of focal length but not all that good either.

<p>In the past couple of decades there have been very few lenses for which the manufacturer used a convertible mode as a selling point. The most recent one that is common is the plain Symmar (which is older than a couple of decades). Contemporaneous with that lens is the plain Sironar from Rodenstock. I have original brochures on each -- neither manufacturer promised top sharpness in the convertible mode.</p>

 

<p>Probably convertibles have fallen out of favor with photographers and the market because the image quality in convertible mode wasn't competitive, particularly with the trend to smaller formats and increased enlargement. Another factor agaist convertible lenses is the trend over the past few decades to less symmetrical lenses, improving performance and made easier with computer calculations. The greater asymmetry means that each cell is less balanced and less likely to function well on its own as a convertible.</p>

 

<p>The Cooke convertible that Brian mentioned is intended for 8x10.

Wisner also advertises sets of convertible lenses: <a href="http://www.wisner.com/Page14.html">http://www.wisner.com/Page14.html</a>.

At one time there were complaints that Wisner was out-of-stock for long times, so I don't know whether or not these are actually available.</p>

 

<p>If someone were interested in experimenting with converting lenses, my guess is that the recently discontinued G-Clarons might be suitable. One could try single cells, or mixing cells from different focal lengths that share the same shutter size. This is only a guess -- maybe worth trying if you already have one or more G-Clarons.</p>

 

<p>Using single cells won't give a long focal length that is usable on a field camera with a shortish bellows. The solution for a camera like the one that Fulvio has is a true telephoto, which is a lens that focus with a bellows extension that is shorter than its focal length. The disadvantage compared to a convertible is that a telephoto lens costs more than unscrewing a cell from a lens that you already have, and it has weight. The advantage for most uses is that the image quality is likely to be better.</p>

Nikon currently makes two sets of convertible lenses.

 

There is the 360mm, 500mm, and 720mm suite. This set will cover both my 4x5 and 5x7

formats. The 500mm and 720mm focal lengths will also cover my 4x10 format as well.

 

The 600mm, 800mm, and 1200mm suite covers up to 8x10.

 

Both sets use interchangeable rear elements. Both sets are optimized for infinity, but I

have done many compositions at shorter distance with very good results. Both sets are

also very slow lenses. This has never been a problem for me. Nether set is cheap. Even

used on ebay they go for a pretty penny. I have the 360-720mm set. All the lens use a

telephoto design which means they require less bellows extension then the actual focal

length.

 

I believe you could use the 360mm with no problem. I suspect you may be able to adapt

the 500mm configuration with an extended lens board.

 

Hope this helps,

Maybe the Nikon T-ED lenses are considered to be "convertible" lenses but they work differently than the traditional convertibles like the Symmar, Cooke, et al others have mentioned in this thread. With the tradtional convertibles you buy one lens and gain additional focal lengths by removing the front or rear element of that lens. With the Nikon telephotos you buy one lens and then gain additional focal lengths by buying additional elements that replace the rear element of the original lens. So if you wish to use say a Nikon 360mm lens as a 500 and a 720 mm lens you buy the 360 lens and the two additional elements. Gaining additional focal lengths with the a Nikon T-ED lens seems more like adding a 1.4X and 2X extender than it does a traditional "convertible" lens but perhaps that's just quibbling over terminology.

I have a brochure from the mid-'70s for the Schneider Symmar-S lenses, where they explain that they had given up tthe convertible feature in order to improve the performance in normal mode.

Thank you all for the answers. But, in one word, there is a way to use the 240-420mm Symmar at 420mm on my Graflex camera? (maximum bellows extensione about 32cm)

Absolutely. You just need to make up a custom lens board incorporating an extension (tube, cone, or box) at least 100 mm long (more if you need to focus closer than the horizon), with a large enough diameter at the rear end to avoid vignetting. Simplest would be a box extension, say, six inches long with the base rim just wide enough to engage the lens board lock on the camera, and the lens mounted to the front surface as with a conventional lens board. Simple construction from 1/8" plywood, painted indide and out with flat black (the outside can be painted any color you like over the black, of course), the extension should only weigh a few ounces. Your movements (especially tilts and swings) will be a little odd with the lens way out there, but IIRC the Graphics (Speed and Crown type) had limited front tilt and no swing in any case; shift and rise shouldn't cause problems.

 

No, of course you won't be able to close the camera with this mounted...

I realize that your question is really asking for recommendations of a model, but I still think that other factors will continue to enter in. Moonrise was shot with a convertible but it was cropped in enlargement, as Adams normally did--so edge sharpness is less an issue. The same issue arises when you use 8x10 instead 5x7 or 4x5--on 8x10 you may be using the whole image circle and with movements the sharpest part may shift around in the image, perhaps into the dirt or the sky rather than where you prefer it.

 

Therefore the longest lens would be preferable because of the larger image circle. These lenses inherently have limited image circles for their length. I see from the published information that the new Schneider XXL large format Art lenses, which tout edge to edge definition, are apparently Dagor design, which means convertible--but I have not heard of anybody tryiung that. They are already rather slow in design, and also rather long for 8x10 in general landscape use.

 

Others have said f22 is sharper than f90, which is true and f22 is acceptable by general standards, but most of the reviews of actual tests that I have seen show peak resolution larger than that--f11 or f16, or even larger, though of course this throws the entire burden of depth of field onto the mercy of style and camera movements.

 

All in all, like the other guys, I am still a bit baffled in that paper (I am told) can only resolve 7 to 9 lines per mm, so that in contact printing the delicacy of any brand name lens (and some coke bottle bottoms) should be lost in the indelicacy of the process. I suspect that lenses with modest coverage (all convertibles and many primes as well), subjected to the demands of style and movements, are being pushed beyond the limits of design.

 

Also, nobody mentioned that long lenses (suitable for 8x10) are nowhere near as brilliant in resolution and contrast as the shorter ones, based on resolution testing. But for most people's money, they don't need to be (and the XXL's may truly be different).