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Topcor lenses
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PostPosted: Mon Dec 04, 2017 6:44 pm    Post subject: Reply with quote
Curiously, the RE GN 50/1.8 is much rarer than the RE GN 50/1.4. Both have exactly the same focusing mechanism, which used a grease that reacted chemically with the brass cam, resulting in the dreaded "green glue". Very straightforward to remove the dress ring, remove the filter thread ring, use screwdriver to remove focusing ring, and then you can see the focusing cam. The optical block is held in by a threaded ring, like in any RE Topcor 100mm or shorter.


PostPosted: Tue Dec 05, 2017 7:15 am    Post subject: Reply with quote
stevemark wrote:
iangreenhalgh1 wrote:
The 1.8/50 isn't a Topcon lens, it's made by Cima Kogaku and not comparable in quality to the real Topcons.


You mix up two things:

1) The Tokyo Kogaku RE GN Topcor 1:1.8 f=50mm is, of course, a genuine Topcon ("Tokyo Kogaku") lens. It was the standard lens for the best-ever Topcon SLR, the motorized Topcon Super DM. We are talking about this lens here; this lens has Guide Number mechanism ("GN") and a zoom-like focusing mechanism without helicoid (see eg http://www.topgabacho.jp/Topconclub/FPslr3.htm for an image of the Super DM with 1.8/50 GN lens).

2) The later RE Topcor 1:1.7 f=55mm was designed and made by Cima Kogaku for Topcon. This has has an ordinary helical focusing (http://www.topgabacho.jp/Topconclub/FPslr5.htm)

Stephan

Steve is correct, the RE GN are Topcon designs that Topcon built.
From the Topcon Story
"In 1976 Topcon had practically arrived at the end of it's rope. Long ago were the times in which their SLR's were exalted in reviews throughout the world.
The competitors had sufficiently closed the gap which separated them from the RE Super and Super DM which, with the addition of the winder, was no more than a revised and corrected RE Super - not enough to save the life of a dozen-year-old camera.
So, probably to empty their warehouses of old lenses and accessories, Topcon put together a new SLR, the economical RE-200, which had nothing in common with its predecessors. It was an SLR without pretensions, accompanied by an outfit of lenses which, like the body, was related to Topcon only by name.
In the series of lenses, called simply RE Topcor, were a wide-angle 2.8/28mm, a medium wide-angle 2.8/35mm, a standard 1.7/50mm (supplied with the camera) and a telephoto 3.3/200mm."


PostPosted: Tue Dec 05, 2017 7:33 am    Post subject: Reply with quote
John Shriver wrote:
Curiously, the RE GN 50/1.8 is much rarer than the RE GN 50/1.4. Both have exactly the same focusing mechanism, which used a grease that reacted chemically with the brass cam, resulting in the dreaded "green glue". Very straightforward to remove the dress ring, remove the filter thread ring, use screwdriver to remove focusing ring, and then you can see the focusing cam. The optical block is held in by a threaded ring, like in any RE Topcor 100mm or shorter.


According to the Topcon Story, Production numbers are:
RE GN 50/1.4 Code 157 B, serial 15700001 to 15703625(last known) is around 4000 copies.
1973, 7 elements, 340g, used a new concept in construction, the only lens to receive anti-reflective coating affirmed by the letter M on the decorative ring. (I think he meant multi coating, as all lenses after WW2 had anti-reflective coatings of some sort)
RE GN 50/1.8 Code 158 B, serial 15800001 to 15805360(last known) is around 6000 copies.
1973, 6 elements, 280g, used a new concept in construction.


PostPosted: Thu Dec 21, 2017 7:34 pm    Post subject: Reply with quote
In terms of appearances on eBay, I'd say the RE GN 50/1.4 is more common than the RE GN 50/1.8. Production numbers may not relate to units in the field. (Maybe the Navy bought a lot of the 50/1.8 lenses and they're still in a warehouse along with the lost ark.)

But I've never seen the unreleased RE GN 35/1.8 on eBay.
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