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.in...ron-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.