Mamiya C Series 135mm lens haze - how to remove the ring(s)?

indy_kid

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So, this is the view through the Taking lens of a Mamiya C Series 135mm. I had the lens out from the rest of the assembly, but the haze is between the last two elements, and the ring holding them is cemented in place.

Is there a solvent that will remove that cement, or is it usual to just cut the ring off, clean the glass, then put on a new ring?

It's not usable at this point.
 

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ags2mikon

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The last 2 elements are cemented. It is a tessar formula (( (). That looks like balsam deterioration.
 

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Is it even possible to do this at home? I figured you would need special equipment to separate the two elements (high heat, most likely) and something to keep the two halves perfectly aligned during re-cementing.
 
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ags2mikon

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It depends on what they used to "glue" the 2 elements together with. Canada balsam comes apart with heating at a fairly low temperature. If it is synthetic it is almost impossible to do. Canada balsam gets cloudy the synthetic does not. If the 2 elements are the exact same outer diameter you can use 2 precision v blocks to align the group together. I have used a small sauce pan with a trivet in the bottom and filled with distilled water to separate them with low heat and done very slowly. You can buy both Canada balsam and UV curing lens cement on line. I did it on a few enlarging lens and a few tessar taking lenses in the past. They worked fine after the repair. What do you have to loose?
 

bernard_L

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Swap the optics between the taking and focusing lenses. Caveat: I don't know whether there are shims to fine-tune positions in respectively taking and focusing optics. Proceed carefully and take notes.

Anybody knows the answer re: possible shims? I'm interested because I have a 180 with a small scratch on the taking optics.
 
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indy_kid

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Good idea! I'll give it a try.
 
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indy_kid

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Swapped the lenses, and the hazed lens works pretty good for a Viewing lens. Will have to do a test with film, but given that the lenses look identical, they should function well as either a Taking or Viewing lens.

It makes sense from a manufacturing standpoint to have the same lens functional as either Taking or Viewing. No need to make 2 different lenses for use in one assembly.

I have the 180mm lens assembly, and the Taking and Viewing lenses look identical as well. Again, no reason to require 2 different lenses when you can use 2 of the same.
 

Dan Daniel

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Well, not to distract from the real topic, but the reason to make different lenses for taking and viewing lens is simple: cost. A viewing lens does not need high resolution, reduced optical defects, etc. since all it is doing is putting a rough image onto ground glass.

Then again, there is a cost to developing a viewing lens, running a second production line to make them, etc. Seems as if Mamiya decided that using the same lenses top and bottom was fine for them. I wonder if they were also thinking about redundancy in case something went wrong with the taking lens, but that's more of a military or NASA mind set.

I know that the Rolleiflex viewing lens is a triplet. Minolta Autocord, also.
 

ags2mikon

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Mamiya used the same lenses top and bottom. I have interchanged them in the past. I've never seen any shims in order to make adjustments. The 135mm is easy since it is all in front of the shutter.
 

Mamiya_Repair

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ags2mikon said:
Mamiya used the same lenses top and bottom. I have interchanged them in the past. I've never seen any shims in order to make adjustments. The 135mm is easy since it is all in front of the shutter.
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The part about Mamiya using the same lenses is mostly true, except for the 80mm f/2.8 S lens, which used a triplet for the viewing lens. As for shims, there actually are several spots where the C lenses use shims: 1.) between the front element and the shutter 2.) between the shutter and the lens board and 3.) between the viewing lens and the lens board. On a TLR like the C series, it's important that both the taking and viewing lenses are focusing at the same spot, so the shims are necessary between the shutter/viewing lens and lens board. The shims between the front element and the shutter adjust for the spacing between the front and rear groups which can vary depending on the production tolerances.
 

Tel

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Which part is scratched? I have a couple of spare front elements for the 180...
 

bernard_L

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Tel said:
Which part is scratched? I have a couple of spare front elements for the 180...
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Thank you for putting this on the table, but the damage on my 180 taking lens is minor, and probably does not affect the image taking in a visible way; I have made a number of pictures that were perfectly OK. Swapping would be more to satisfy the perfectionist in me. I have come to learn that in camera repair one should know where to stop because every intervention has also a share of risk.
 
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