rdeloe
Well-known member
Very nice! I'm going to look into this to see if I can replace my janky solution with a nice circular shim of the correct dimensions. This is incredibly inexpensive. I'm astonished they can do this.
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comparision between Digaron-W 50 mm, Grandagon 65 mm, Biogon 53 mm
- Thread starter Alkibiades
- Start date
Paul Spinnler
Well-known member
Amazing buildbot! I can't stress enough how I am always amazed when you draw stuff out of your hat! I think shimming one's own lenses is one of the best possible hacks in lens land as the alternative is to send it to Rodie or so who will charge you an arm and a leg nowadays.
Your handle incidentally is very fitting here!
Paul Spinnler
Well-known member
What's the useable IC you get on the 43 again?This kind of thing is a lot easier if you're OK with "janky" solutions.
This is my Mamiya N 43mm f/4.5 L after modifications. I couldn't find a circular shim the right diameter, but I had a piece of brass that was curved and the right thickness. I cut two pieces: one for each side. You can see one of them here. I "temporarily" wrapped the join with electrical tape; it's still there because it works, and I'm all about function rather than pretty.
By the way, this was a fascinating example of how this can all get weird when you're adapting lenses. Bill Rogers (awesome Mamiya tech in Nevada) did the gut job on the innards, and as part of that process he uses the correct Mamiya tools and procedures to confirm that the right shim is in place and that the spacing is perfect. This is the equivalent of "Send it back to Rodenstock". Weirdly, the correct spacing for a Mamiya 7 is completely wrong for a GFX camera. Image quality at the "correct" spacing was horrendous. I had to use the procedure I described above to get to a spacing that worked for GFX. If I was only using this lens on my F-Universalis, the fact that I'd now lost infinity wouldn't be an issue; it's a unit focusing lens that I focus with the F-Universalis. However, I also use this on an adapter I made for hacked Mamiya 7 to GFX. To make this lens usable on that adapter, I had to adjust the helicoid. All my other Mamiya 7 lenses required no adjustment of cell spacing. It's strange, but it works superbly well so I'm fine with the jankiness.
View attachment 207501
buildbot
Well-known member
Me too, this kind of stuff has gotten really easy and cheap fairly recently I feel!
Thank you very much
Lens shimming is one of those things that I feel should be more DIY but the knowledge of how to do it well seems pretty secretive and hard to find, at least until people here have begun posting more about it!
rdeloe
Well-known member
The Mamiya N 43mm lens is designed to cover 6x7, which would mean ~87mm at infinity. However, to answer what you really want to know, someone is going to have to lend me a medium format back and the bits I need for my F-Universalis! I can't get past 4mm on my setup with GFX because the rear end is inside the mount.
My N 65mm and N 80mm can handle 20mm shifts on GFX, which means a circle of good definition of ~90mm. The circle of illumination on the 80mm goes on and on beyond that, which is why the light falloff characteristics of the 80mm are so good.
Paul Spinnler
Well-known member
I am asking because there's this new adapter on ebay which takes IQ4 on one side and GFX adapters on the others. The 43 would be nifty little lens
Hah, janky or not, it's the result that counts! In reality this isn't rocket science. TBH the biggest mental block I had was actually unscrewing the lens cell from the shutter for the first time. But once I got over that (it took a little encouragement) I realized how simple the process really is.
John
John
rdeloe
Well-known member
That would be a nice portable outfit if the image quality is good on the sensor. You'd need to figure out a custom mount. I used three parts to build this one:
1. GFX to M65 adapter
2. M65 helicoid
3. Cut-down Mamiya 645 Extension Tube 1
A fair bit of "machining" was needed. By that I mean filing, cutting, drilling and tapping -- basic stuff that a reasonably handy person can manage.
There are lots of ways to do this with different bits and pieces. I used a helicoid because it gives me a much better close focusing distance than the lens helicoid provides.
John Leathwick
Well-known member
I can also attest to the gains from shimming - or in my case, making sure that the shim was seated properly. Partly on Rob's recommendation, I bought a Schneider ApoComponon 90 for use with my F-Universalis, and it was okay when unshifted but quite meh with any movement at all - a result that was completely contrary to Rob's experience and what the on-paper specs indicated should be the case. I checked out a number of potential causes, but nothing I tried made any improvement, leading me to eventually consider replacing it. However, after hearing of Rob's experience with his Mamiya 80mm, I decided to check out the rear element to see if I could tweak it into a better space. When I removed the rear element I found that there was a shim, but it was sitting on quite a tilt. I carefully seated it flat onto collar around the front of the rear element, screwed the rear element back into place and Voila! I had a totally different lens! I'm now quite happily shifting this lens 8-10 mm with quite acceptable results - a much cheaper solution than a trip back to Germany!
-John
-John
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Alkibiades
Well-known member
you should put the shimming rings on the front element not at rear. especially for wide angle lenses it will be a big difference.
I shimmed the front cell as a matter of convenience. Can you explain the rationale for doing so from the actual optics perspective? Thanks.
John
Alkibiades
Well-known member
all modern lenses from rodenstock- schneider have the rings only at the front element. There are some older lenses, where there are ring- but different in the rear element, becouse some lens-shutter combos need it: at some wide angle lenses the rear glass simply touched the shutter blades.
my first digital lens was the Digitar XL 47 mm. The cornerss were realy bad. I send the lens to schneider and made a call with the technician. He told me that the calibration ring was on the wrong element- on the rear, so he simply chaged it and add it on the front. This costs about 100 euro (15 years ago). This was the first time I learned something about the calibration, and indeed the lens was simply great after that.
my first digital lens was the Digitar XL 47 mm. The cornerss were realy bad. I send the lens to schneider and made a call with the technician. He told me that the calibration ring was on the wrong element- on the rear, so he simply chaged it and add it on the front. This costs about 100 euro (15 years ago). This was the first time I learned something about the calibration, and indeed the lens was simply great after that.
diggles
Well-known member
I'm assuming this is a file you created and uploaded to their system. Would you mind sharing it?
What are the inside and outside diameters?
Thank you!
Warren
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buildbot
Well-known member
Hi Warren! It is! I don't mind sharing it at all - I actually had to revise it, twice, and it is still possibly not quite right - I used a weird polaroid press shutter that was next to me, in combo with the copal shutter specs on sk Grimes; which mislead me I think. Planning to survey my variety of shutters and see if I can tune the measurements more exactly, then I will post it here! Sometime tomorrow hopefully!
You are very welcome!
- Max