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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!


PostPosted: Mon Nov 29, 2021 3:30 am    Post subject: Reply with quote

Eric Hendrickson (pentaxs.com) re-cemented the doublet in the short-mount 100/4 Bellows Takumar for me. I don't know if he'd consider working on a Bronica lens element. I don't know how fancy his centering setup is.


PostPosted: Mon Nov 29, 2021 9:14 am    Post subject: Reply with quote

justtorchit wrote:



Thanks for sharing that info here. I have done my best to avoid using Facebook for quite a few years now


With you 100% on that one. Assume to join any Facebook group one would be required first to join Facebook. For me that will NEVER happen. In addition:

While I have an intense, truly abiding, interest in lens repair . . . .

I have absolutely zero interest in camera repair, aside from lenses.

I'm also in the USA, like yourself, and over many years have been envious of the access Europeans have to competent and affordable lens repair services on their continent. I'm unaware of anything even close here in North America, where high prices seem to me the order of the day if, indeed, one is able to locate competent lens repair services in the first place.


PostPosted: Mon Nov 29, 2021 12:37 pm    Post subject: Reply with quote

This is likely a modern lens cement which won't come apart unless heated to high temperatures or soaked for a long time in something nasty like methylene chloride. Traditional Canada balsam on older lenses does melt at much lower temperatures, but no chance that will have been used in a Bronica PS lens.

I would say you will likely pay less for another copy of the PS 35mm compared to having it repaired for you. I have no experience with Bronica lens repairs, so I don't know if the doublet was edge-ground to fit the cell precisely post-centering (likely though), in which case a V-block would suffice for adequate alignment when cementing (assuming you maintain exactly the original rotational alignment of the flint & crown).

Another obvious DIY route would be to see if you can find a cheap 35mm PS with damaged front optics/shutter and use that as a donor for the rear optics, assuming you know how to re-collimate Bronica PS lenses.

guardian wrote:

I'm also in the USA, like yourself, and over many years have been envious of the access Europeans have to competent and affordable lens repair services on their continent. I'm unaware of anything even close here in North America, where high prices seem to me the order of the day if, indeed, one is able to locate competent lens repair services in the first place.


Well, I live in Europe and I doubt whether affordable lens repair services extend to re-cementing doublets. Wink (it is usually specifically mentioned as a service not offered, together with coating repairs/re-coating...)

I've never understood camera repair quotes anyway. I serviced a few Minolta STR's myself and I cannot believe that the usual quoted CLA prices for these involves all that is required.

For example, replacement of all light baffles; Minolta SRT's have a hidden, but important and often disintegrating one sandwiched between the camera chassis and the bottom of the mirror box, which requires removal of the mirror box (it prevents light leaks when left without either a lens or body cap mounted for some time in bright conditions, which is leaking in past the aperture actuation lever). I just can't believe that is covered in the usual quoted prices given the pain involved in removing a mirror box from an SRT (removing top & bottom, leatherette, removing lens mount, de-soldering wires, removing cables, pulleys, removing pentaprism & focussing screen, removing mirror box, replacing baffles, replacing mirror box, readjusting mirror box alignment & checking connection clearances, refitting focussing screen & prism, rethreading cables & pulleys, re-soldering wires, refitting lens mount, recalibrating lens mount alignment and lens register, recalibrating focussing screen, adjusting shutter speed indicator, adjusting EV indicator, recalibrating light meter, re-glueing leatherette and putting the top & bottom back on). All that priced at a couple of hours' work??? I bet that light baffle under the mirror box gets conveniently overlooked in most "CLA"s, but it will gradually spread its disintegration "dust" throughout the mechanism. Crying or Very sad


PostPosted: Mon Nov 29, 2021 1:35 pm    Post subject: Reply with quote

John I may reach out to Eric and just see what he says. Can't hurt! Thanks for all the input so far.

RokkorDoctor wrote:
This is likely a modern lens cement which won't come apart unless heated to high temperatures or soaked for a long time in something nasty like methylene chloride. Traditional Canada balsam on older lenses does melt at much lower temperatures, but no chance that will have been used in a Bronica PS lens.

I would say you will likely pay less for another copy of the PS 35mm compared to having it repaired for you. I have no experience with Bronica lens repairs, so I don't know if the doublet was edge-ground to fit the cell precisely post-centering (likely though), in which case a V-block would suffice for adequate alignment when cementing (assuming you maintain exactly the original rotational alignment of the flint & crown).

Another obvious DIY route would be to see if you can find a cheap 35mm PS with damaged front optics/shutter and use that as a donor for the rear optics, assuming you know how to re-collimate Bronica PS lenses.


Good to know - I hadn't really considered that possibility (that it isn't even balsam that's being used). I'm just beginning to dig into this stuff as I keep coming across vintage glass with separating elements and I have been frustrated that the most economical solution is usually "buy a better copy" or parts swapping. The latter being especially difficult with some of these more rare optics. I do believe this doublet is ground flush and I did have a V-block shipped to me. But I recently returned it, thinking I'm not quite ready to have a go at this yet as the lens is still usable and I would hate to really screw things up.

I'm all ears to more experiences and ideas.


PostPosted: Wed Dec 01, 2021 10:04 am    Post subject: Reply with quote

Idk if he can or will touch this lens but I've had a lens recemented from a guy in Taiwan once, and it turned out perfectly fine (The lens was a Contax 28-85mm).

I think it's worth writing him a mail. Waiting times for the repair might be long (3+ months) though.

http://lens-cla.blogspot.com/p/blog-page_19.html


PostPosted: Wed Dec 01, 2021 2:08 pm    Post subject: Reply with quote

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.

This. Just try yo be very careful with commenting, they ban people without hesitation and without warnings.

As far as actual recementing goes, if the doublet sits in a setting, or you can come up with a way to make your own to align the elements, you can probably try it at home. If not, and you are not willing to take a loss it's probably better to replace the lens.


PostPosted: Wed Dec 01, 2021 9:53 pm    Post subject: Reply with quote

For alignment, a V-block with an end plate(3 adjacent surfaces on the inside corner of a cube) made out of hardwood should be an inexpensive project to make a useful tool that will hold the elements reasonably close to their optical centres assuming they were manufactured properly, and have enough exterior surface to self align when placed in the V-block, most doublets I've seen would have enough surface in contact with the V-block to not have any issues with finding alignment.