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Services For Re-cementing A Doublet in 2021? DIY?
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PostPosted: Wed Nov 24, 2021 5:20 pm    Post subject: Services For Re-cementing A Doublet in 2021? DIY? Reply with quote

I came into a rather rare fisheye lens for my Bronica SQ system (the PS 35mm f/3.5) at a fairly good price given it's rarity. Unfortunately the price was a result of some mild haze or separation in the rear optical assembly. I opened it up and the issue is between two bonded elements. It's enough that strong highlights, such as a setting sun, in a certain part of the frame, does affect the final image (some veiling, lack of contrast).

As a DIY'er, and having read a lot of these posts, I can see lots of info from photographers and astro folks who heat their doublets up in the oven (or toaster oven) and have in some cases reported getting rid of the issue then and there. More commonly, they're merely doing this to separate the optics. Then using solvent to clean them entirely. And either re-cementing with balsam or UV-cured optical adhesive (like Norland NOA 63). I have a very rudimentary understanding of this process, but did go down the path of considering purchasing the NOA 63, a UV lamp, and a V-block to hopefully separate and re-cement my doublet. Heck, because I love this stuff, I even checked out Opto-Alignment's youtube videos on their optical benches and wondered "How much do those cost...."

But given the rarity of the optic, again, I have held off, still searching to see if there are any services out there who still do this. I am located in the US. Has anyone done this at all? Have any recommendations? I reached out and did get one response from Duclos Lenses. They put the repair in the ballpark of $1000 (also aware it could be well over the value of the lens). I see some broken links on past posts of similar nature though indicating the previously recommended services no longer exist.

The last option is just live with it, perhaps until a better copy comes along. I really just enjoy fixing things and would love to get this back to original spec.







PostPosted: Wed Nov 24, 2021 5:37 pm    Post subject: Reply with quote

You would probably need an optical bench in order to reliably recement lenses like it is done here: https://www.youtube.com/watch?v=cl6K-EXPILo


PostPosted: Wed Nov 24, 2021 5:55 pm    Post subject: Reply with quote

As always, you should join the learn camera repair Facebook group, because there are countless discussions and examples on doing this, what not to do, how much will it cost to do a better job etc.

I'll copy from one of the comments I found particularly illuminating:

white paper on cementing doublets from one of the larger precision optics shops in the US: https://www.photonics.com/images/Web/WhitePapers/53/Assembly_Method_Considerations_for_Cemented_Assemblies.pdf
Keep in mind that Optimax usually works to a higher level of precision (and cost!) Than typical consumer photographic equipment.
Excellent results can be achieved with an air bearing and a <$100 mechanical test indicator like you'd find in any machine shop. And the air bearing is probably overkill. A precision ball or roller bearing would likely work.
It all depends on how sensitive the design is to the doublet assembly tolerance. Unfortunately this is difficult to estimate without the full prescription of the lens.


PostPosted: Thu Nov 25, 2021 12:05 am    Post subject: Reply with quote

D1N0 wrote:
You would probably need an optical bench in order to reliably recement lenses like it is done here: https://www.youtube.com/watch?v=cl6K-EXPILo


I mentioned this video (and company) in my initial question. I am aware.



eggplant wrote:
As always, you should join the learn camera repair Facebook group, because there are countless discussions and examples on doing this, what not to do, how much will it cost to do a better job etc.


Thanks for sharing that info here. I have done my best to avoid using Facebook for quite a few years now and was pretty upset when they bought Instagram as it was one of the few social media channels I used. Working to pry myself off that one too - unfortunately with few alternatives, that's where a lot of people still try to connect. But that's a whole other topic.

Yeah I was kind of wondering how close I could get to a workable result by way of some maybe even used pieces of equipment (you mention the air bearing or roller bearing and the mechanical test indicator). Even if I could make something in the neighborhood of sub $500, where maybe I could then do some more. Repairing a few of my other optics, I think it would be worth it to me. Not to mention the value of the learning along the way!