Sironar S lens SHIMS - lens experts help needed

[paul_4875]

I am fitting my Littman with a 135mm sironar S, but when I unscrewed the front element from the copal 0 shutter, I find a small shim set between the lens and shutter, really thin - perhaps a fraction of a mm - obviously put there by Rodenstock, as its a brand new lens.

However, the Littman requires that the front element is removed often to close the camera. I will loose this shim at some point if I have to do this, so I wondered: can I put it on the rear element unit, thus maintaining the lens' rear-of-front-section to front-of-back-section distance, or is it affecting something else?

perhaps someone can also explain the purpose of such a shim, although how to get around it is more important than the theory for now..

[Vamsi M]

Hi,

This is a question which can only be answered authoritatively by an optical engineer. Perhaps the company rep. can put you in touch with one.

I have read (I think on usenet) that the shims are critical to maintain the performance of the lens. The precise placement of the stop can affect the performance of a lens, so I would not mess with it. It may well be that the loss of sharpness won't be noticed in many situations, especially in a handheld camera. However, in my opinion, if you've spent the extra money on a Sironar-S for it's technical performance, it doesn't make sense to degrade that characteristic.

Vamsi

[Frank Petronio]

Why are you wasting a Sironar-S on a Littmann? It's not like you need the coverage. I would trade you an shim-less N plus $$$ for the S....

[paul_4875]

a sironar S is not just about coverage Frank - it's able to shoot a stop faster (i.e. a stop wider open)
which is rather important in a hand held camera.

[James E Galvin]

The spacing between the elements is much more critical than the stop placement, so moving the shim to the back should OK.

[Ole Tjugen]

If it's a stop faster you need, I'll trade you a Schneider Xenar Series 1C 150/3.5 for it - it cost me all of $40...

[paul_4875]

thanks Jim, that's what I suspected, but needed an expert like you to confirm.

interestingly enough - the mounting threads inside the otherwise identical Copal 0 shutters are different - so... I need to swap the shutter unit as well as the lens element units, which is annoying, as its a tight squeeze in this camera.

(it has an apo symmar 150 in Copal 0 at present)

[paul_4875]

"If it's a stop faster you need, I'll trade you a Schneider Xenar Series 1C 150/3.5 for it - it cost me all of $40..."

what is this - a street vendors market?? largeformatbarter.com??

I need ultimate resolution at a wider than normal aperture.
there's only one modern multi coated lens that specifically does that - the Sironar S.

[Ole Tjugen]

I just couldn't help myself...

But form my experience, the difference between older singlecoated and modern multicoated lenses in terms of sharpness, resolution and contrast is overrated. Will the resolution still be "ultimate" when the shim has been moved - or even removed?

I also have a (single-coated) Planar 135/3.5 which will have to be pried from my cold, dead hands.

[Michael Jones]

Praying I do not get flamed for this suggestion: email Bob Soloman at HP for the answer.

bob at hpmarketingcorp dot com

Good luck.

Mike

[Michael S. Briggs]

As Jim says, the spacing between the two cells is the critical parameter. If the cell-to-aperture spacing were critical, then there would be lenses with shims on both the front and rear cells, which I have never seen. So you should be able to move the shim to the rear cell. Manufacturers put the shim on the front cell because the typical uses is less likely to remove this cell and possibly damage the shim.





The reasons for the shim are explained in Interchanging lenses in Copal Shutters. Why does it work? at
http://www.largeformatphotography.info/lfforum/topic/498712.html (http://www.largeformatphotography.info/lfforum/topic/498712.html).

[adrian tyler]

off topic but i really like a lot of your work paul, also some of the best large prints i-ve seen in the madrid exhibition last year.

keep it up!

adrian

[Frank Petronio]

Nothing personal against Paul, but I enjoy torturing people who drink Reverend Littmann's Kool-Aid (and maybe Gurrilliemosio will even grace us with a 300 word rant...)

Isn't saddling a Polaroid 110b conversion - even if the Littmann conversion costs $3000 - with the job of providing 'ultimate resolution" asking an awful lot for a plastic camera with folding, stamped steel standards, and imprecise alignment? Wouldn't a lowly (and cheaper!) Linhof Technika (with a properly set-up rangefinder) keep things more perfectly aligned and tight so you could take advantage of that "ultimate resolution?" After all, the Linhof's rangefinder has a wider distance between the RF windows (more accurate) and has a solid mechanism that isn't going to shift with use and as the body loosens.

(I once had a 110b conversion and found the Yaserex to be pretty damn good, at least at real-world scanning resolutions and shooting wide open (which I think it was meant to do).)

[Bob Salomon]

There is something else to consider. The front element threads are not designed to take on and off by the user. Cross thread them while doing so and you are in for a very expensive repair.

[Glenn Kroeger]

Since the front and rear threads on a Copal 0 shutter are the same (M29.5-0.5) I cannot see how the ones on the front are "not designed to take on and off by the user"?

[Glenn Kroeger]

To finish that thought... both front and rear threads are the same. But what I assume Bob is getting at is that NEITHER is designed for constant and repeated usage such as every time the camera is folded. Another problem with repeated disassembly is that the lens elements at the threaded ends of the front and rear assemblies are not protected by any rim so the chance of damage is not insignificant.

[Bob Salomon]

Right on Glenn. removing and replacing elements regutrly in a shutter is inviting damage to the threads as well as exposing the shutter blades to mechanical damage as well as dust. Cleaning dust off the blades is what can lead to the mechanical damage.

[paul_4875]

of course, none of you doom mongers are wrong, and it is good to have it pointed out, but... what about all those convertible element lenses out there? the ones where you are supposed to screw everything in and out, back and forth front to back, every time you use them? and not just old time classics - the Cooke convertible sold out entirely of its first production run in a few weeks.

the threads on the copal 0 are not the same, (or maybe the shutters come to rodenstock the same as to schneider, but they are fitted with internal threads that make them different sizes). The front element of a modern 150 Apo Symmar taken from a Copal 0, will not go onto a 150 Sironar S threaded copal 0. different sizes.

[Frank Petronio]

Nothing against you Paul, it's just that many of us don't like Littmann as a person. His cameras are cool if you can rationalize buying them.

[alban christ]

I am affraid that Littman is well respected amongst his peers as a photographer and as a person. his cameras are great and no need to rationalize anything, what is abominable and impossible to rationalize instead is to choose hate and torture and admit that gives someone pleasure, what gives me joy is taking photos.

I am getting a second Littman with a removable front element, I have allready ordered one.
these concerns are dumb, for one thing the belloows on any camera is more fragile than the thread on any front element, this as not stopped anyone...