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GN Topcor M 50mm f/1.4
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PostPosted: Tue Dec 18, 2018 1:27 pm    Post subject: GN Topcor M 50mm f/1.4 Reply with quote

Hi everyone, I'm curious about this lens. How does it compare to other 50's? And more importantly is it one of those lenses you like use or is it one of those that just sit on a shelf or cabinet collecting dust?

Samples I have found on google looks good, bokeh looks complicated, a bit like the Olympus 50mm f/1.4.


PostPosted: Tue Dec 18, 2018 3:04 pm    Post subject: Reply with quote

It would be interesting to see examples from a full-frame camera. However I'm more interested in GN 50/1.8


PostPosted: Tue Dec 18, 2018 5:51 pm    Post subject: Reply with quote

No first hand experience here. The weird bokeh and overall feel didn't really convince me. Also the RE. GN is known for horrible lube => need for relubing.

TBH the only improvement over the RE. 58/1.4 are coatings.


PostPosted: Wed Dec 19, 2018 5:33 pm    Post subject: Reply with quote

Alright, good heads up about the grease. I already have a 58mm 1.8. But that GN 50 1.8 also would be interesting to try out.

And the 58 f/1.4 looks good as well, but I'm more interested in lenses with thorium glass.

It seams rare enough that no owner has answered yet.


PostPosted: Thu Dec 20, 2018 3:51 am    Post subject: Reply with quote

I don't know how to describe, but I really like results from this lens.
I had CZ 50/1,4 hft, pentax 50/1,4M, fujinon 50/1,4, konica 50/1,4 AR all sold now, and tried some other 50/1,4 lenses. This lens is different, but you have to zoom to 100% to see.
https://ihyaahsani.blogspot.com/2014/01/tokyo-kogaku-topcor-re-gn-m-5014.html

and here's from recent shot with a6000


Last edited by IAZA on Thu Dec 27, 2018 3:37 am; edited 1 time in total


PostPosted: Thu Dec 20, 2018 12:38 pm    Post subject: Reply with quote

Thanks for posting! Interesting that you left all those good 50's for the Topcor.


PostPosted: Fri Dec 21, 2018 8:28 am    Post subject: Reply with quote

RE Auto Topcor 5.8cm f1.4


RE GN Topcor M 50mm f1.4


RE GN Topcor 50mm f1.8

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


PostPosted: Fri Dec 21, 2018 11:15 am    Post subject: Reply with quote

The transition from 58 to 50 mm is quite interesting. For the F1.4 variant the 7/5 concept was kept and for the F1.8 one they changed from 6/6 to 6/5.
Would be curios to see the the differences for the F1.8 lens.


PostPosted: Sat Dec 22, 2018 4:43 am    Post subject: Reply with quote

More from http://www.topgabacho.jp/Topconclub/lenscut.htm

Auto Topcor 5.8cm f1.8 (code 28B)


F Auto Topcor 5.8cm f1.8 (Topcon Story says it's code 62B and it's a copy of the 28B)


RE Auto Topcor 5.8cm f1.8 (I'm 99% sure this is a 62B, there are 2 versions 99B & 129B that are not on the Topcon Club site, assuming they both have no doublet in the front, they probably look more like the GN below)


REGN Topcor 50mm f1.8


Copied from one of my posts, data from Topcon Story.
Code 62B based on the F Auto-Topcor from: 620001 to 625115 (1963)
Code 99B new optics,2nd and 3rd elements were separated. from 99xxxxx to 9901920 (1964)
Code 116B new mechanicals, from 1160001 to 11608302 (1965)
Code 129B (black or chrome) optics changed again From: 1161xxxx to 11670435 last known (1966) I have the chrome version, awesome lens.
Code 129BD (Navy) from: 1165xxxx to 11650401 last known (1967)
Code 129BG AUTO-TOPCOR (black) from: 1168xxxx to 11685922 last known (1971)


PostPosted: Sat Dec 22, 2018 5:39 am    Post subject: Reply with quote

Thanks for posting. Obviously I mixed something up. All F1.8 lenses are 6/5 but different designs.
Nonetheless the differences betw. the last 58mm and the GN 50mm would be interesting.


PostPosted: Sat Dec 22, 2018 10:54 am    Post subject: Reply with quote

tb_a wrote:
Thanks for posting. Obviously I mixed something up. All F1.8 lenses are 6/5 but different designs.
Nonetheless the differences betw. the last 58mm and the GN 50mm would be interesting.

An interesting blog post.
http://pakira3.sakura.ne.jp/wp/?p=29094
I use the "simple translate" add-on in Firefox, works great.


PostPosted: Sat Dec 22, 2018 12:10 pm    Post subject: Reply with quote

Quite interesting that they didn't produce these lenses themselves.

Obviously Minolta was a very rare bird within the camera and lens industry. They even had their own glass factory. Wink


PostPosted: Sat Dec 22, 2018 2:06 pm    Post subject: Reply with quote

I would have to see more evidence that shows anyone else made their lenses other than the zooms and late RE's.

From Topcon Story
In 1935 Tokyo Kogaku/Topcon's president Shinohara acquired Ohara Optical Glass, a division of the Hattori group which supplied -among others- Nippon Kogaku, Ohara went on to supply glass to Asahi and Seiki Kogaku(Canon). https://www.oharacorp.com/about.html https://www.ohara-gmbh.com/en/ohara/chronik.html https://global.topcon.com/about/history/ http://www.guidafotousato.it/4-STORIA_MARCHE/testi/TOPCON.htm


Something is odd about that lens, where's it's serial number?
http://pakira3.sakura.ne.jp/wp/?p=29094


28B




62B



99B


116B


129B


129BD(Navy)



129BG


RE GN


RE Topcor (Not made by Topcon)


PostPosted: Tue Dec 25, 2018 10:48 pm    Post subject: Reply with quote

Lightshow wrote:
I would have to see more evidence that shows anyone else made their lenses other than the zooms and late RE's.
Exactly. This part sounds strange - ordering the original 58s from Tomioka and the GNs from Shima/Siema. Topcon should be rooted to glass production. These days it produces parts (even higrade interchangeable camera lenses!) for big players such as Canon, Nikon, Olympus or Fuji via its Optonexus Co., Ltd. subsidiary.


PostPosted: Sat Feb 16, 2019 12:54 am    Post subject: Reply with quote

I would not be surprised if the RE GN Topcor lenses (50/1.8 and 50/1.4) were from a different factory for the metal parts. The stop-down lever isn't in a ball-bearing race, the lens mount is chromed brass instead of aluminum, etc. These same differences are also in the 500/5.6 lens. They were the last three Topcors that went into production. (The 28/2.0 and 35/1.8 were prototyped but not released. The 28/2.0 is old-style, the 35/1.8 was RE GN style.)

I could believe that Topcon might have outsourced the metal work. But Tokyo Optical have been glass makers and lens grinders for a long time, and are still supplying other brands. For instance the linked pages show they are supplying glass to Fuji. I suspect they're behind some of the work for Cosina as well.

As for the page describing the all-aluminum helical as crude, I don't buy that. They are beautifully machined, but being aluminum on aluminum, they are dependent on proper lubrication. The brass-on-steel helical of Nikkors are much tougher, but make for heavy lenses. The Super D was so heavy Topcon made aluminum lens bodies to compensate. Plus, they had been using aluminum (beautifully finished) back into the LTM era.

One thing that is distinctively "Topcor" is the use of selected shim tubes for collimating the infinity focus of the RE,Auto-Topcor lenses. These shims go between the lens barrel and the helical. This isn't the method used on the RE GN lenses, where the marked focusing collar is held to the helical with four flat screws, and that is adjustable for the infinity stop. The same collimation by focusing collar technique is used on Pentax-M and later lenses (at least). Now if that selected shim was common with other Tomioka manufactured lenses, that would be an interesting hint.

I do give Pentax a nod for the much more clever and efficient mechanical engineering of their mechanics in the Pentax-M and later lenses. (Might be the same in the earlier ones, I've just never torn one down.) The lens barrel has the aperture on the inside, and one set of helical threads on the outside -- so less parts in the lens. The Topcor barrel is spaced from the helical with the shim, and held in with a lock ring at the front. More parts.