Using a G-Claron as a convertible lens?

[Greg]

Was just wondering if anyone had ever tried using their G-Claron as a convertible lens... only using the front or rear group of optics? In my case specifically a 355mm G-Claron on 11x14. Just looking to not have to go through 2 sheets of 11x14" HP-5 plus film for the front group and another 2 sheets of film for the rear group.
thanks

[jnantz]

hi greg

i haven't done this, and i haven't used my 150 as a convertible
but there are people who have done stuff like that :)
http://www.largeformatphotography.info/forum/showthread.php?110660-G-Claron-casket-set

[Dan Fromm]

As John has already pointed out, its been done. The general rule -- Bob Salomon will tell us that it doesn't apply to Rodenstock lenses -- is that a lens is converted by removing the front cell. Since G-Clarons are symmetrical, which cell is removed shouldn't matter very much.

[Bob Salomon]

As John has already pointed out, its been done. The general rule -- Bob Salomon will tell us that it doesn't apply to Rodenstock lenses -- is that a lens is converted by removing the front cell. Since G-Clarons are symmetrical, which cell is removed shouldn't matter very much.

Except that by removing the front group the shutter becomes very vulnerable!

[Mark Sampson]

I recall when I first had access to a Schneider 180/315 convertible Symmar. I didn't have a long lens of my own and I took the Symmar out. Removed the rear group and tried a photo or two. It was a longer f.l. but terribly unsharp in the edges and corners of the 4x5 frame. I was disappointed but thought, "oh well, they said it was only good for portraits".
Some years later, after the internet, I found that you were meant to use the rear group as the single part. So I thought to try that out. By then I owned a Nikkor-M 300/9, so I had something to compare it to. The rear-element 315 did pretty well... better than its reputation. I never tried it again because I had the answer already; 20 years later I still use that Nikkor.
Moral of story: Fred Picker's old motto, "TRY IT".
Yet I still wonder why any manufacturer who offered a convertible lens didn't include a threaded fitting to replace the missing front group, to protect the shutter (per Mr. Salomon) and provide for attaching a filter or lens hood. And a case for the removed front group, as well. But that's whole 'nother question.

[jnantz]

i had a friend who was a repair guy who moved to FLA years ago
and he used to tell me that any lens can be a convertible lens
he never would say how good or bad it would be though LOL

i always wondered about the kodak portrait lenses ..
did they ever sell a clear glass "skylight filter" for them to
protect the shutter seeing the whole lens
was only a rear group?

[Dan Fromm]

i had a friend who was a repair guy who moved to FLA years ago
and he used to tell me that any lens can be a convertible lens
he never would say how good or bad it would be though LOL

Triplet? Tessar?

[Pere Casals]

Anyway think that "non convertible" plasmats don't have the individual cells alone corrected, it's the full assembly that's well corrected, so resolving power performace of a single cell can be lower than figured.

Then you should expect soft corners until you stop a lot, and also you should check if you have focus shift, so if you focus wide open then you may need to check focus again after stopping to shot, this may require a tight cloth because dim image.

I've a collection of 4 symmar convertibles, and using the 360 (brick, 2kg) converted to 620 (half brick, 1kg), very happy with the coversion, assuming mentioned limitations.

[Greg]

So tried using the front element group of my 355 G-Claron with the aperture stopped down 3 stops from wide open on my 11x14. Center was tack sharp, but the image sharpness just gradually deteriorates as one gets further and further away from the center of the image. Image quality many, many steps down from the 355 in its normal configuration. Judging the negative on a lightbox, and I am of the opinion that it wasn't good enough for contact printing.

[Pere Casals]

Well, still it can be used creatively for a sort of tunel view.

The lens you would like is the fujinon c 600, I guess, but this is $3k...

I got my Symmar 360 convertible to 620 for under $300, and it was Technika stamped, in nice compound 4. This is having two focals, and the 620 conversion at f/12 it's not an slow glass for a 620mm covering a large circle.

[jnantz]

Triplet? Tessar?

hi dan
he never differentiated which types
just said any lens could be used that way ..

[Dan Fromm]

He's an ignorant fool.

[jnantz]

He's an ignorant fool.
not sure about that, i've removed lens cells from a bunch of lenses that i have
and used them converted, or other ways and they work fine ...

[Louis Pacilla]

i had a friend who was a repair guy who moved to FLA years ago
and he used to tell me that any lens can be a convertible lens
he never would say how good or bad it would be though LOL

i always wondered about the kodak portrait lenses ..
did they ever sell a clear glass "skylight filter" for them to
protect the shutter seeing the whole lens
was only a rear group?


Triplet? Tessar?


hi dan
he never differentiated which types
just said any lens could be used that way ..


He's an ignorant fool.


not sure about that, i've removed lens cells from a bunch of lenses that i have
and used them converted, or other ways and they work fine ...

Hey John I believe brother Dan has brought up two optical designs which WILL NOT deliver a usable image when converted and in some cases NO image at all. The Tessar and the Triplet are two such examples of nonconvertible lens designs. NOT ALL LENS designs ARE CONVERTIBLE

[Dan Fromm]

Thanks, Lou. Checking before speaking or posting rarely hurts.

[jnantz]

Hey John I believe brother Dan has brought up two optical designs which WILL NOT deliver a usable image when converted and in some cases NO image at all. The Tessar and the Triplet are two such examples of nonconvertible lens designs. NOT ALL LENS designs ARE CONVERTIBLE

hi louis
i use elements from tessars all the time
i said " i have used them converted or other ways"
i didn't need to do research on the topic seeing i have personal experience ...
( sorry i don't have or know what a triplet is or might be so i can't say anythng about that )

https://www.photrio.com/forum/media/red.55480/
https://www.photrio.com/forum/media/outside.55478/#media
can't please everyone ..

i also use a 127 tominon 4.7 as a lens on my 4x5, i was told more than once
for some weird reason that it doesn't cover a 4x5 sheet of film.
mine has covered fine, so far ... for 30years ... ;)

YMMV

[mdarnton]

The supposed reason to generally use the elements, front or back, behind the shutter is that the dodgy outer edges of the lens are automatically cropped off by the shutter size. That's why the old convertibles were all intended for the component being used to be moved to the back. I'm not sure I swallow that, but I do notice that when I use the front half of my Wolly Tele as a SF lens, the results are considerably "better" when the front is used on the back then if I leave it on the front. And the difference is large. This is following the practice of the old landscape lenses, also, which put the aperture ahead of the glass when it could have just as easily been used the other way around.

[Bob Salomon]

The supposed reason to generally use the elements, front or back, behind the shutter is that the dodgy outer edges of the lens are automatically cropped off by the shutter size. That's why the old convertibles were all intended for the component being used to be moved to the back. I'm not sure I swallow that, but I do notice that when I use the front half of my Wolly Tele as a SF lens, the results are considerably "better" when the front is used on the back then if I leave it on the front. And the difference is large. This is following the practice of the old landscape lenses, also, which put the aperture ahead of the glass when it could have just as easily been used the other way around.

Except Rodenstock’s instructions were to leave the front cell in place and remove the rear cell with the old, convertible Sironar.

[Pere Casals]

Oldest symmar convertibles had 3 aperture scales, for both cells mounted, for the front one and for the rear one.

I guess that they removed one scale simply because to avoid confusion.

Removing the rear cell like Rodenstock recommends it shortens the required bellows amount and protects better the shutter.

Removing the front cell like Schneider recommends requires more bellows amount but it's easier to remove and to fit the front cell, for example with an studio camera when you do half body portraits or headshots.

IMHO both, with old covertible rodenstocks and symmars, we can use the front or rear cell alone, but we should use the one that has the right aperture scale, if not we have to meter with a probe in the back.

[Paul Ewins]

FWIW, and slightly off topic, I have the 1931 Schneider catalog which has a table showing the focal lengths and apertures of each cell of the Angulon, so being "convertible" was obviously seen as a desirable feature for any lens that was suitable.