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troublemaker
Joined: 24 Nov 2003
Posts: 715
Location: So Cal
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 Posted: Sun Dec 11, 2005 2:05 am Post subject: |
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What is this? I have a General SCientific lens here that came with some other lens stuff a long time ago and it says it is a Ser. III 10 in. F:6.3 It is reasonably sharp even with the back element really scratched up. Since I just got a GVI I thought I might make a G-10 lens board for it. So I am just curious if anyone knows about these or has some data. Big and heavy and at least has what looks like the purpleish single coating of the Optars.
Thanks,
Stephen |
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Dan Fromm
Joined: 14 May 2001
Posts: 2146
Location: New Jersey
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| Posted: Sun Dec 11, 2005 10:52 am Post subject: |
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On 2005-12-10 18:05, troublemaker wrote:
What is this? I have a General SCientific lens here that came with some other lens stuff a long time ago and it says it is a Ser. III 10 in. F:6.3 It is reasonably sharp even with the back element really scratched up. Since I just got a GVI I thought I might make a G-10 lens board for it. So I am just curious if anyone knows about these or has some data. Big and heavy and at least has what looks like the purpleish single coating of the Optars.
Thanks,
Stephen
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Please count reflections and make a guess about construction. If four strong, no weak, reflections from the glasses in front of the diaphragm and two strong, one weak from the glasses behind the diaphragm, it is a tessar type. If 4,0 and 4,0, dialyte or four element double Gauss (less likely). If 4,1 and 4,1, plasmat or six element double Gauss (less likely).
I've never found any documentation about General Scientific lenses, they're mysteries.
Cheers,
Dan |
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troublemaker
Joined: 24 Nov 2003
Posts: 715
Location: So Cal
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| Posted: Sun Dec 11, 2005 4:40 pm Post subject: |
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Shutter closed I see front: One large, and the small dim one barely dicernable. Back: Two Large, and two small. So then I Pressed the shutter open while looking at the front and the four images from the back appeared. The one dim image I am seeing on the front is half as bright and noticeably smaller than all the others which are bright. The front large image is purple while the ones coming form the back are not and refelcting the color given off by the desk lamp. Color Corrected?
For comparison I looked at a 135mm late Optar. Four front, all bluish. Back, one large pink and one small dim. This appears almost exactly the opposite from the big ten inch (sorry).
For consistency (since this is a "Scientific" test) I checked a 101 Optar too, and same as 135.
Reverse Tessar?
I like that, Mystery lens. This thing has been put away for a couple years now and I have a funny feeling I am going to like the results. I think it cost ten bucks. Someone has glued a filter ring on it which will probably discourage me form removing the cells on the front.
regards,
Stephen
[ This Message was edited by: troublemaker on 2005-12-11 08:41 ] |
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Dan Fromm
Joined: 14 May 2001
Posts: 2146
Location: New Jersey
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| Posted: Sun Dec 11, 2005 5:40 pm Post subject: |
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On 2005-12-11 08:40, troublemaker wrote:
Shutter closed I see front: One large, and the small dim one barely dicernable. Back: Two Large, and two small. So then I Pressed the shutter open while looking at the front and the four images from the back appeared. The one dim image I am seeing on the front is half as bright and noticeably smaller than all the others which are bright. The front large image is purple while the ones coming form the back are not and refelcting the color given off by the desk lamp. Color Corrected?
For comparison I looked at a 135mm late Optar. Four front, all bluish. Back, one large pink and one small dim. This appears almost exactly the opposite from the big ten inch (sorry).
For consistency (since this is a "Scientific" test) I checked a 101 Optar too, and same as 135.
Reverse Tessar?
I like that, Mystery lens. This thing has been put away for a couple years now and I have a funny feeling I am going to like the results. I think it cost ten bucks. Someone has glued a filter ring on it which will probably discourage me form removing the cells on the front.
regards,
Stephen
[ This Message was edited by: troublemaker on 2005-12-11 08:41 ]
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Sounds like a reversed tessar, coated too.
The Vade Mecum mentions some reversed tessars that it says are good at distance. FWIW, all of the reversed tessars I've had have been macro lenses. One, a 100/6.3 Reichert Neupolar, is also very good at distance but with, alas, limited coverage.
Please do take a few shots with your mystery lens and report back.
I just got another ten buck mystery lens, a 180/6.8 Fotokopist Spezial Reproduktions Optik. Uncoated, I'm afraid. Nothing much about it on the web, so I'll have to use it to find out what its good for. Not much is the most likely answer, but at least I'll know.
Cheers,
Dan |
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troublemaker
Joined: 24 Nov 2003
Posts: 715
Location: So Cal
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| Posted: Sun Dec 11, 2005 7:15 pm Post subject: |
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I need to get it mounted on a GV board. I am going to make a batch of these out of G-10 (epoxy fibre board, very strong). I only held the lens flush with the edge of the PAcemaker adapter board, but image on GG looked pretty good, perhaps better than what I am used to with older single coated Optics. Though I was kinda joking about the reverse Tessar, I thought I had heard of this before, so just threw it out there. When I use it I will remember this post and bring it back.
Stephen |
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Dan Fromm
Joined: 14 May 2001
Posts: 2146
Location: New Jersey
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| Posted: Sun Dec 11, 2005 7:44 pm Post subject: |
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| Quote: |
On 2005-12-11 11:15, troublemaker wrote:
I need to get it mounted on a GV board. I am going to make a batch of these out of G-10 (epoxy fibre board, very strong). I only held the lens flush with the edge of the PAcemaker adapter board, but image on GG looked pretty good, perhaps better than what I am used to with older single coated Optics. Though I was kinda joking about the reverse Tessar, I thought I had heard of this before, so just threw it out there. When I use it I will remember this post and bring it back.
Stephen
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Good luck. FWIW, in my experience what you see on the GG with a lens wide open doesn't predict very well how well the lens will put image on film, especially when stopped down. |
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troublemaker
Joined: 24 Nov 2003
Posts: 715
Location: So Cal
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| Posted: Sun Dec 11, 2005 9:44 pm Post subject: |
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Yes, it's always an adventure, and I have had some interesting surprises. The good, the bad, and the ugly.
I do not know only a little regarding using movements (need to read up on it and test), but I will do some with this and see what happens. I also tend to shoot more loosly than I used to and leave room for crops on stuff that is important for me.
Stephen |
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RichS
Joined: 18 Oct 2001
Posts: 1468
Location: South of Rochester, NY
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| Posted: Wed Dec 14, 2005 6:48 am Post subject: |
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Sorry for being late, and not being much help anyway 
I looked in the book and there is a General Scientific Corp from 4829 S. Kedzie Ave., Chicago, Ill.
There are listed 4 lenses, two 19", a 24" and a 30"; all process lenses. No image circles or configurations for them. They're all listed in barrel...
Even if it's a process lens, it may make good photos... Good luck with it...
_________________
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"Ya just can't have too many GVIIs"
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troublemaker
Joined: 24 Nov 2003
Posts: 715
Location: So Cal
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| Posted: Thu Dec 15, 2005 4:16 am Post subject: |
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well thanks rich. the f-stop scale is hand written on the shutter, but not the lens, that is engraved and painted. I thought it might be a special purpose thing.
Stephen |
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