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Archive 2023 · Canon FD 50mm 1.2L rear element

wa666ou
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p.1 #1 · p.1 #1 · Canon FD 50mm 1.2L rear element

I have a Canon FD 50mm 1.2 L lens with a scratch on the rear element. This produces unwanted artifacts when shot against highlights at wide apertures. So, I have been trying to find out if I can replace that rear element.

Now, finding a new rear element is pretty impossible. I could get another 50L with some other damage, but that's also a rare occurrence.
I also contacted a local Canon dealer and they don't have any info on the availability of this part from the factory.

My question is - does this lens have a unique rear element or does it share it with some other models (aka cheaper)?
I have checked some lens schematics that I could find on Google, but nothing.

See this image

Oct 09, 2023 at 02:09 AM

jcolwell
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p.1 #2 · p.1 #2 · Canon FD 50mm 1.2L rear element

Yeah, that artifact looks pretty annoying.

I did a little comparison shopping of block diagrams, and (as you found) it's pretty unclear if the FD and EF have the same elements, or not. The only observaion I can make, is that the rear element of the FD appears to be slimmer, but block diagrams are more symbolic than geometrically-accurate, and so this isn't conclusive.

I did some calculations based on ratios of filter diameter to front element diameter from FD images, and measurements from my EF 50/1.2L This shows that the front element diameter of the FD is about 41.5mm, while the EF is 45.0mm (measured). This suggests they are different optically.

Finally, I just measured the nose-to-nose distance between front and back elements on my EF 50/1.2L, and it's 58.0mm (+/- 0.5mm). This exceeds the overall length of the FD 50/1.2L (50.5mm, Canon Museum) by at least 7mm, and so I think this shows that there are real differences in optical geometry.

Anyway, while you're watching for a donor element, you might try this:

I've had success with reducing (and effectively eliminating) bad flare artifacts from a scratch in the lens surface (through the coating), by filling the scratch with black ink. The artifact shown in your images looks more like a shadow, but I figure it's worth a try. Keeping 'stray light' away from the inner edges of the scratch, may eliminate the problem (as it does for more obvious 'flare' problems). I'd start with washable ink.

Cheers,
Jim

P.S. Welcome to posting on FM.

Oct 09, 2023 at 07:11 AM

wa666ou
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p.1 #3 · p.1 #3 · Canon FD 50mm 1.2L rear element

Thanks for your reply!

I was hoping that perhaps FD 50mm 1.2 nfd would also be the same size, but I can't find any technical info. I do have 50/1.4 nfd, but I seriously doubt this has the same element.

The black ink is a good idea! Thank you!

I forgot to upload the image of the scratch itself. It does have a shadow.

Image of the scratch

Oct 09, 2023 at 07:19 AM

jcolwell
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p.1 #4 · p.1 #4 · Canon FD 50mm 1.2L rear element

That is nasty. Let us know how it goes.

Oct 09, 2023 at 07:27 AM

wcj0
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p.1 #5 · p.1 #5 · Canon FD 50mm 1.2L rear element

how about trying to find out the type of glue that they fill cracked windshields with or using cynoacolade which is probably spelled wrong.

Oct 09, 2023 at 07:38 AM

wa666ou
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p.1 #6 · p.1 #6 · Canon FD 50mm 1.2L rear element

wcj0 wrote:
how about trying to find out the type of glue that they fill cracked windshields with or using cynoacolade which is probably spelled wrong.

I will try black ink first.
You mean probably cyanoacrylate glue aka super glue. Not sure if I want to put that on my lens. I would if it would be 50 $ 50/1.4

Oct 09, 2023 at 09:23 AM

Photonadave
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p.1 #7 · p.1 #7 · Canon FD 50mm 1.2L rear element

If you are not satisfied after trying out the black ink suggestion, which I agree will likely reduce the light scatter visible in the central area of your example picture, then consider instead to just selling your
lens for parts or repair since they appear to be in short supply however going this route depends on what you are willing to spend on resolving this problem by purchasing another used same lens replacement in good working order.

Oct 09, 2023 at 07:16 PM

wa666ou
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p.1 #8 · p.1 #8 · Canon FD 50mm 1.2L rear element

Well, as the lens works well in every other situation I would not sell it as "for repair/parts". It's still a wonderful lens. But, I have been considering getting a flawless one instead. I love FDs and 50L is one of the must-haves.

See some of my FDs

Some sample photos of highlights and bokeh (shot with Fuji X-H2).
Highlights 1
Highlights 2
Bokeh 1
Blur 1

Oct 10, 2023 at 01:13 AM

rscheffler
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p.1 #9 · p.1 #9 · Canon FD 50mm 1.2L rear element

wa666ou wrote:
My question is - does this lens have a unique rear element or does it share it with some other models (aka cheaper)?
I have checked some lens schematics that I could find on Google, but nothing.

See this image

I don't think the black ink trick will solve the problem for the type of bokeh image above because that bokeh artifact is basically a shadow and not light scatter. So filling with black ink will just make it even more of a shadow.

The scratch seems like a scuff and not so much a gouge into the glass, so filling it with something clear might be tricky.

https://www.mir.com.my/rb/photography/companies/canon/fdresources/fdlenses/50mm.htm

The above link suggests that the FD 50/1.2 non-L is actually a revision of the FD 50/1.4 and the FD 50/1.2L is a unique design with aspherical element and floating element focusing system. The very small block diagrams also imply that the rear element in each f/1.2 design is different and wouldn't be interchangeable. I think based on this the L lens has a unique rear element compared to other Canon 50mm designs from that era. The rear element of the EF 50/1.2L is considerably different - much thicker than the very thin rear element of the FD 50/1.2 L.

Other info:

http://www.marcocavina.com/articoli_fotografici/Canon_FD_50_1,2_L/00_pag.htm

Oct 10, 2023 at 02:13 PM

wa666ou
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p.1 #10 · p.1 #10 · Canon FD 50mm 1.2L rear element

So, I tried the black ink solution and indeed, the shadow remains and it doesn't fix the situation. I have read that some people have used car windshield repair kit and it has worked for them.

Anyway, seems like the best is to sell the lens and get a new one.
There are some okay deals on eBay. Might try to find one from FB groups from the EU.

Thank you, everyone, for sharing your thoughts!

Oct 11, 2023 at 01:06 AM

wa666ou
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p.1 #11 · p.1 #11 · Canon FD 50mm 1.2L rear element

Here I shot a video of how it performs against highlights.

Oct 11, 2023 at 05:04 AM

Photonadave
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p.1 #12 · p.1 #12 · Canon FD 50mm 1.2L rear element

wa666ou wrote:
Here I shot a video of how it performs against highlights.

It looks like the scratch is near the edge of the element where it shows up in the out of focus highlight near the end of the video?

For stills this would likely be easy to remove in post however dunno about video. Perhaps a bit tedious if there are a large number of out of focus highlights.

Is this with the black ink filling the scratch? Either way I think it will show up in out of focus highlights.

Oct 11, 2023 at 06:06 AM

wa666ou
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p.1 #13 · p.1 #13 · Canon FD 50mm 1.2L rear element

Yes, in photography this is not a major issue, can be fixed in the post. Not so sure about in the video.
This sample was shot after I had applied the ink.

Anyway, I listed the lens at local FB groups. With a good price (450 EUR) it should find another home. Because I want to use it for video too, I prefer the lens without such a fault.

Oct 11, 2023 at 06:21 AM

jcolwell
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p.1 #14 · p.1 #14 · Canon FD 50mm 1.2L rear element

I would hope the ink (or whatever crack filler) would reduce the colour artifacts visible in the video, but would not affect the shadow. Maybe, it would darken the shadow, but eliminating the colour bloooms would make PP much easier, if it works. I have done this successfully with two or three lenses, on both front and rear elements, but that was for slender scratches through the coating. This is more of a deep rub.

Have you tried anything like ROR* to see if some of the mark can be cleaned away?

* Residual Oil Remover (a liquid glass cleaner)

Oct 11, 2023 at 06:27 AM

wa666ou
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p.1 #15 · p.1 #15 · Canon FD 50mm 1.2L rear element

I shall clean the ink with isopropanol later and take a closer look with my 2:1 macro lens.
It's hard to tell with my eyes, what exactly is there.

Oct 11, 2023 at 06:42 AM

jcolwell
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p.1 #16 · p.1 #16 · Canon FD 50mm 1.2L rear element

If you want to 'fill' the crack with something more-or-less clear, I suggest you try "fish glue". It's very water soluable. Among other things, I use it to 'fix' adapters thay are too loose (a drop of fish glue in the right place), and similar issues. A single drop of water on the 'solid' drop of fish glue, softens and releases it in a second or two.

On second thought, a more modern water-soluable glue might be worth considering, as some of them are very clear.

Oct 11, 2023 at 07:09 AM

Robin Smith
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p.1 #17 · p.1 #17 · Canon FD 50mm 1.2L rear element

Just don't get it wet then

Oct 11, 2023 at 02:19 PM

wa666ou
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p.1 #18 · p.1 #18 · Canon FD 50mm 1.2L rear element

Well, I took out my macro 2x lens and zoomed in. This scratch is not deep, although I can barely feel it with my finger, so the depth is very small.
But, filling it with glue or something... not sure this can be done!

The scratch

Oct 12, 2023 at 03:05 AM

Photonadave
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p.1 #19 · p.1 #19 · Canon FD 50mm 1.2L rear element

Hmm, was there a fingernail file in the camera bag along with the lens uncapped?

Oct 12, 2023 at 04:35 AM

rscheffler
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p.1 #20 · p.1 #20 · Canon FD 50mm 1.2L rear element

wa666ou wrote:
Well, I took out my macro 2x lens and zoomed in. This scratch is not deep, although I can barely feel it with my finger, so the depth is very small.
But, filling it with glue or something... not sure this can be done!

The scratch

I’d just leave it.

If you can’t find another one, there is a guy in Taiwan who can remove the scratch, but it will remove the coating on that surface. I considered doing this for a Leica lens I have and I think the price was around $400 US. In the end I sent it to Leica to replace the element for about 2x more.

Oct 12, 2023 at 06:56 AM

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