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Topcor 8cm f5.6
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PostPosted: Fri Feb 16, 2018 3:41 pm    Post subject: Topcor 8cm f5.6 Reply with quote
Anyone see this one before?
https://www.ebay.com/itm/TOPCON-Topcor-8cm-F5-6-for-35A-w-Finder-case-EXCELLENT-from-Japan-9746/282842452522


http://www.topgabacho.jp/Topconclub/lens8.htm

Quote:
This lens is TOPCOR 8cm f5.6 for Topcon 35A & 35B. This lens was manufactured from '53 through '55. The lens constitution is 3groups 5lenses. In the case that we use this lens in Topcon35A, need the exclusive use finder. The Topcon 35B has equipped with the other focusing ring for the 8cm lens.


PostPosted: Fri Feb 16, 2018 4:29 pm    Post subject: Reply with quote
Yep, see it quite often advertised at quite high prices...


PostPosted: Sun Feb 18, 2018 4:55 am    Post subject: Reply with quote
Has anyone used one?
I assume it's adaptable, I'm curious about how good it is.


PostPosted: Sun Feb 18, 2018 5:14 am    Post subject: Reply with quote
With such large front element and 3groups/5lenses design, the design may be similar to the Tele-Xenar. It may be a decent lens but I am not sure. Wink


PostPosted: Fri Jul 30, 2021 12:08 pm    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:48 pm; edited 1 time in total


PostPosted: Fri Jul 30, 2021 6:28 pm    Post subject: Reply with quote
Blazer0ne wrote:
Why was it so slow? It's not an enlarging lens nor indicated for large format.

The Topcon 35 was made in early 1950's and uses a Copal shutter, it has an interchangeable mount.

https://camerapedia.fandom.com/wiki/Topcon_35
Quote:
The only major change that occurred during the production of the Topcon 35A was the switch from the Toko 4cm f/3.5 standard lens, presumably having three elements, to the Topcor 4.2cm f/3.5 with four elements.

The standard lens has f/3.5 maximal aperture. It is screwed to the front of the shutter and it is interchangeable


So the aperture/shutter is a fixed size built into the camera, and adding a longer focal length but using the same shutter/aperture limits the lenses speed to f5.6 @ 80mm focal length. https://en.m.wikipedia.org/wiki/F-number
If they had built a wider focal length lens, it's speed would have been faster than f3.5... Assuming it's even possible back then to design a shorter focal length at the same mount distance.


PostPosted: Tue Aug 10, 2021 1:24 am    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:48 pm; edited 1 time in total


PostPosted: Tue Aug 10, 2021 1:40 am    Post subject: Reply with quote
Looks closer to 40mm to me, the filter size of the lens on the camera looks to be in the 20-30mm range.


PostPosted: Tue Aug 10, 2021 1:47 am    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:48 pm; edited 1 time in total


PostPosted: Tue Aug 10, 2021 2:09 am    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 4:11 pm; edited 1 time in total


PostPosted: Tue Aug 10, 2021 4:05 am    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 4:11 pm; edited 1 time in total


PostPosted: Tue Aug 10, 2021 6:03 am    Post subject: Reply with quote
That looks very different from the lens in the first post, if this the actual mount, what's attached to the lens in the first post picture?

Any pictures to share?


PostPosted: Tue Aug 10, 2021 4:56 pm    Post subject: Reply with quote
I think the lens in the advert is mounted in the base of a plastic bubble but that is just a guess.


PostPosted: Wed Aug 11, 2021 2:17 am    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:48 pm; edited 1 time in total


PostPosted: Wed Aug 18, 2021 11:50 pm    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 6:33 pm; edited 1 time in total


PostPosted: Thu Aug 19, 2021 6:53 am    Post subject: Reply with quote
A bible base makes sense, cool, makes it infinitely more adaptable.

They make thread pitch gauges to identify unknown thread sizes, a machine shop should have one, they can also make an adapter for it, if their price is too steep, give RAF a shout, the hardest part will be to get the clocking between the threads and the mount such that the DOF scale ends up at 12:00.
I would probably use a LTM to E mount adapter as the starting point if the registration is far enough, speaking of which, any idea what the registration distance is?


PostPosted: Thu Aug 19, 2021 4:33 pm    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:49 pm; edited 1 time in total


PostPosted: Thu Aug 19, 2021 10:33 pm    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:49 pm; edited 1 time in total


PostPosted: Thu Aug 19, 2021 11:37 pm    Post subject: Reply with quote
Blazer0ne wrote:
Lightshow wrote:

I would probably use a LTM to E mount adapter as the starting point if the registration is far enough, speaking of which, any idea what the registration distance is?


I don't have the original camera, but check out the photo from above with the 15-26mm focus helical for a good idea on registration.

It looks like I need 1mm / 25.4tpi threads for the RMS adapter.

Unfortunately that doesn't narrow it down much as I don't know where within that 15-26mm range infinity happens...
18mm (camera mount register) + 1mm (camera mount to helicoid) + 15-26mm (helicoid) + 1mm (helicoid to lens adapter) = 35mm-46mm a range bigger than the range of SLR mount registrations.

Lightshow wrote:

A bible base makes sense, cool, makes it infinitely more adaptable.

Curses you autocorrect... bubble*


PostPosted: Thu Aug 19, 2021 11:47 pm    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 4:11 pm; edited 1 time in total


PostPosted: Mon Aug 23, 2021 4:12 pm    Post subject: Reply with quote
I have this lens as well as a Topcon 35A and 35B bodies. The lens comes in a metal case and mounts in the piece you see in the photo. Also there is the piece which holds the finder and it screws into the bottom. Such a neat presentation. My lens has some optical challenges as I just had it cleaned as well as possible but does have many wipe marks on the front element. The one I purchased is only the second or third I have ever seen in 20 yrs on Ebay, and there still maybe one out there for lots of $$$ from Japan.

I also have a Minion 35A and even though it's lens has a very similar mount, I don't believe these lenses were meant to be interchageable? I have never tested with film but the 35B is a real prize!




For some reason, I am unable to reply to your comment but I'll take some photos of the Topcon 35A and 35B with the lens mounted and of the complete case.
Have never tried to adapt these to any other system so I am at a loss when it comes to how they might register???
Regards,
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Last edited by hilltime on Tue Aug 24, 2021 6:34 pm; edited 2 times in total


PostPosted: Mon Aug 23, 2021 4:25 pm    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 4:11 pm; edited 1 time in total


PostPosted: Wed Oct 27, 2021 10:01 am    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 4:11 pm; edited 1 time in total


PostPosted: Wed Oct 27, 2021 9:01 pm    Post subject: Reply with quote
Nice collection of Topcon cameras.
I'd love to see some pics from the 4.2cm & 4cm, I think I've only seen grainy film shots.


PostPosted: Wed Oct 27, 2021 9:15 pm    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:05 pm; edited 1 time in total
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