A lense you didn't know you had

Curt · Jun 26, 2006

I was reading about lenses and found the statement that all Schneider Symmars S lenses are convertible. I found the statement several time and I was thinking that the lens I had to have for Brooks Institute for a first lens was a 210 5.6. I bought a Schneider and today after reading about convertible Schneiders I mounted the lens and took off the front element and wow there it was, a very clear image at twice the length. I wonder why there was never an f stop label for two lengths. Is this just a characteristic of these lenses and those who use them as convertibles do so because they are in the know? I checked the same with my Schneider Xenar 150 and by removing the front element I was able to get a clear image on the gg. The image was about half the size of the two together. It's clearly not designed as a convertible but there is a good image none the less. I would have to test it to see. The Symmar leaves no question as to being a convertible.

Any thoughts on convertible lenses like these?

Curt

Ole · Jun 26, 2006

All Plasmats, Dagors, Rapid Rectilinears and Aplanats, Periskop, Protar and so on are "convertible" in that they give a recognisable image with one half removed. Unsymmetrical lenses like Tessars (Tessar, Xenar, Skopar and lots of other names), Heliars and Triplets are not.

There's been some speculation that the only difference between the Symmar f:5.6 and the Symmar-S is the lack of a second f-scale...

Amund · Jun 26, 2006

Curt said:
I was reading about lenses and found the statement that all Schneider Symmars S lenses are convertible. I found the statement several time and I was thinking that the lens I had to have for Brooks Institute for a first lens was a 210 5.6. I bought a Schneider and today after reading about convertible Schneiders I mounted the lens and took off the front element and wow there it was, a very clear image at twice the length. I wonder why there was never an f stop label for two lengths. Is this just a characteristic of these lenses and those who use them as convertibles do so because they are in the know? I checked the same with my Schneider Xenar 150 and by removing the front element I was able to get a clear image on the gg. The image was about half the size of the two together. It's clearly not designed as a convertible but there is a good image none the less. I would have to test it to see. The Symmar leaves no question as to being a convertible.

Any thoughts on convertible lenses like these?

Curt

I just got a 150mm Symmar-S and reading your post, I had to try this myself, and you`re right! Any idea what the real aperture is when removing the front element?

TheFlyingCamera · Jun 26, 2006

Expect at LEAST 2 stops less...
your mileage may vary.

Donald Qualls · Jun 26, 2006

Amund said:
I just got a 150mm Symmar-S and reading your post, I had to try this myself, and you`re right! Any idea what the real aperture is when removing the front element?

Fortunately, it's easy to calculate the correct figure. With the front group off, measure the focal length (easy way: take the difference between the two infinity positions, and add it to the known focal length of the whole lens), then directly measure the aperture diameter (which will, in this configuration, not be magnified by the front group, so will be smaller than the effective aperture of the whole lens). Do this once, and you'll get a relative aperture, or "f stop" -- compare that to the value on the existing scale, and you'll have a difference in stops, which will be constant over the whole scale.

On my 150/5.6 Componon (optically similar to a Symmar, but originally made for enlarging), I haven't done all of this yet, but a close estimate puts it at about 2.5 stops difference -- f/5.6 with the whole lens is approximately f/12.5 with the rear group only. This is approximately the same correction I've read of for the Symmar -- that is, f/5.6 for the whole lens, and about f/12 to f/12.5 for the rear group.

You could probably also do this by setting up the camera to view an artificially lit, evenly colored surface, and using your light meter to measure the brightness of the ground glass when focused on the surface in both configurations.

Changeling1 · Jun 26, 2006

I have a straight (no S) Symmar 5.6 /150 mm that converts to a 12/265. There are two f scales. It's in a Linhof shutter. It's a very nice lens but is quite heavy. I wouldn't want to leave it on a wooden camera for extended periods of time and wouldn't use it at all on any wooden "super-light" 4x5.

But back to the subject at hand- There need not be a "S" on the Symmar 5.6 convertible lens for it to have two f scales.

removed account4 · Jun 26, 2006

one thing to remember is that with the front element removed there will be a little bit of softness. should make a nice portrait wide open

metod · Jun 26, 2006

Ive got Schneider Symmar 240mm/f 5.6 and it also doubles as 420mm/f12, so you indeed loose about 2 stops of light. Luckily, mine is clearly marked with 2 focal lengths in different colors, otherwise I would not be aware of that. One thing not to forget is that if used without an element, one must add about 2 extra stops on f scale markings, so let's say f22 will become f45.

MurrayMinchin · Jun 27, 2006

Well, slap my ass and call me Judy!!!

I'd never heard that before.

Murray

Christiaan Phleger · Jun 27, 2006

Whack! Judy. You're welcome.

epatsellis · Jun 27, 2006

Changeling1 said:
I have a straight (no S) Symmar 5.6 /150 mm that converts to a 12/265. There are two f scales. It's in a Linhof shutter. It's a very nice lens but is quite heavy. I wouldn't want to leave it on a wooden camera for extended periods of time and wouldn't use it at all on any wooden "super-light" 4x5.

But back to the subject at hand- There need not be a "S" on the Symmar 5.6 convertible lens for it to have two f scales.

Gee, I guess I'll have to post a pic or two of my 360 f5.6 componon on a Toyo 45D then, it works quite well. I use a front mounted packard on it. at least til my 360 5.6 symmar arrives. Then it goes into an enlarger.

erie

Markok765 · Jun 27, 2006

Tamron 28 2.8, konica hexanon 57 1.4

Donald Miller · Jun 27, 2006

I have one of these lenses and the focal length converts from 210 to 370 (not quite double the focal length of the combined elements). The F stop for the 210 length go from 5.6 to 45 and the F stop F12 to F45 with the F 45 designation being almost to the F 22 designation on the 210 aperture scale.

The lens that I have is the Symmar...no S...I also have a 210 F5.6 Symmar S. I have never used the convertible feature on either lens.

epatsellis · Jun 27, 2006

here's a couple of pics of the Componon 360 on the Toyo 45D........

erie

argus · Jun 28, 2006

Changeling1 said:
I have a straight (no S) Symmar 5.6 /150 mm that converts to a 12/265. There are two f scales. It's in a Linhof shutter. It's a very nice lens but is quite heavy. I wouldn't want to leave it on a wooden camera for extended periods of time and wouldn't use it at all on any wooden "super-light" 4x5.

But back to the subject at hand- There need not be a "S" on the Symmar 5.6 convertible lens for it to have two f scales.

That's correct:
only the older Symmars (non S) seem to have been labelled convertible by Schneider.
They are interesting for backpaking and light travel. The little added weight does not compete to having to carry another lens around.

G

Peter De Smidt · Jun 28, 2006

When you use a lens with it's front lens cell, you may want to try a yellow filter to cut down on the increased aberrations.

Steve Smith · Jun 28, 2006

"A lense you didn't know you had"

I didn't know I had one of these. I've had a look and I still don't think I have one!

Steve.

(p.s. it's lens not lense !!)

argus · Jun 28, 2006

Peter De Smidt said:
When you use a lens with it's front lens cell, you may want to try a yellow filter to cut down on the increased aberrations.

Do you mean "with the rear cell removed"?

Thanks,
G

Ole · Jun 28, 2006

I've use my 240/420 Symmar (no S) in the "converted mode", with the front cell removed. I saw no ill effect on neither sharpness nor fringing, and did not use a filter. Additionally the scene I wanted to capture was 200m away and 75m down, so I had to use all the drop possible on my 5x7" camera. That means that I was very close to the edge of coverage. The negative was still as sharp as one shot with any decent (not great) 420mm lens, and the prints are sharper than they would have been by cropping out the corresponding bit from a negative shot with the whole lens.
And that's the main reason for converting lenses: Even if it's not as sharp as a "prime" lens, it's better than half as sharp as the whole lens.

Curt · Jun 28, 2006

--------------------------------------------------------------------------------

"A lense you didn't know you had"

I didn't know I had one of these. I've had a look and I still don't think I have one!

Steve.

(p.s. it's lens not lense !!)
__________________

The word "lense" is a variant of the word "lens", and though I am not an Oxford graduate, I am a University graduate and sometimes prefer to use the word "lense". If you Goggle "lense" you will get nearly 5,000,000 hits. They are using the variant also.

Stay flexible,
Curt

Steve Smith · Jun 29, 2006

Curt said:
The word "lense" is a variant of the word "lens", and though I am not an Oxford graduate, I am a University graduate and sometimes prefer to use the word "lense". If you Goggle "lense" you will get nearly 5,000,000 hits. They are using the variant also.Curt

Damn. You're right!!!!

But you got Google wrong so we're even!!

Steve.

Curt · Jun 29, 2006

Yes but Google wasn't in the APUG dictionary and I don't do the "G" much. The modern convention is "lens" though, I must be showing my age.

Best Regards,
Curt

jstraw · Apr 13, 2007

I found this thread after making my comment in the Cooke convertible thread and read with interest. I have 150 Symmar S but what really intrigues me is my 210. Now mine happens to be a 210 Componon S and while I'm just guessing, I don't think I'm getting quite as much increase in focal length when I remove the front element but it's wonderfully diffuse with it off and the aperture wide open. I think I've discovered that I have a lovely portrait lens.

jimgalli · Apr 14, 2007

Any symmetrical lens will focus light singly. Even some non symmetrical ones, like Verito's. Dagor's are poor as singles. Schneider used to advertise the 6.8 Angulon as a convertible. My most used G-Claron is a 225mm. A mis match of a 240 front with a 210 back. It's one of the sharpest lenses I own.

Curt · Apr 14, 2007

I had mine for years and never gave a thought to it being convertible. Then who would really. It's a nice bonus isn't it?

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