Cell distance in shutter

[Math]

In my search for looking for a cheap Copal #0 shutter, I discovered I already owned one. The Polaroid 110A with Yashinon 127mm was mounted in a Seikosha shutter with aperture stopping down to f/90, and a top speed of 1/500.

I want to use the shutter to mount a 135mm Symmar lens, but due to some obstructions on the shutter, I can't mount the front cell very deep. This means there is about 2mm of extra distance when the cells are mounted in the shutter, then when mounted in the barrel they came in. How big of an impact does this have on image quality, when mounted on a 4x5"?

It looks fine on the groundglass, but that doesn't say a lot of course.

[Archphoto]

It can affect the image quality.
The best way to check it out is either on the GG with a magnifier or make a testshot on b&w film and then use a magnifier or make a print and then use the magnifier.

Q: could you post a pic of the shutter with the 135mm lens showing the obstruction ?
It would be easier to come up with a solution.
Thanks,

Peter

[Math]

I'll have to make a print, I suppose. Would take a while before I have access to the enlarger though. Also, slightly off-topic, Schneider lists the filter thread to be 0.5mm, yet all the step up rings I see on eBay are 0.75mm. Where would I be able to get a 0.5mm step up ring to 49mm with normal filter thread?

Also, here are the pictures:



As you can see, the raised bevel marked with Polaroid blocks the front cell.

[Peter K]

The wrong distance in the tenths of a millimeter influence the image quality, specially at the outer area of the image circle. So 2 millimeters are intolerable.

Where would I be able to get a 0.5mm step up ring to 49mm with normal filter thread?

Step up rings are made by e. g. Schneider and Helioplan.

[Bob Salomon]

The Symmar 135mm had a 40.5 x 0.5mm filter thread. Heliopan makes both filters and step-up rings in 40.5 x 0.5 thread. You should have no problem ordering these from your camera store. A 40.5 to 49mm step-up ring to fit your lens is Heliopan code 700226. Those are special order and would take about 30 days for delivery. We do have the more popular 700216 ring in stock which is 40.5 to 52mm. That you can order from your camera store as well.

[Archphoto]

OK, if you are handy:

Remove screw 1 (a tiny bastard, don't loose it)
Remove ring 2

Now you can take-out ring 3

Mark ALL positions first !

If ring 3 is hollow at the point where my arrow ends you are out of luck, otherwise you can file away the excess material until it is level with the rest.

Clean ring 3 and remount in the reverse order.

Peter

[Archphoto]

Sorry, here is the photo

[ic-racer]

Lens spacing affects the flatness of the field. In your case I'd predict a shift in the edges to focus farther out toward infinity. Central rays shouldn't be affected much.

[Math]

Thanks for the help, and thanks for the idea Archphoto. I had a similar idea, but I suppose filing away the excess is indeed a lot easier then making a flat replacement ring!
Thanks!