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03-21-2011, 08:33 AM   #1
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What does O <---> C mean on a lens? (Quantaray 400mm f/6.3

I'm guessing Open/Closed? If I'm wrong could someone correct me, please?

I just bought a cheap ($8!) Quantaray 400mm lens which has some sort of screw mount adapter on it. It seems to work just fine on my K-x, except it has the mysterious O <--> C ring on it. The "C" setting only seems to work at the wide open 6.3 aperture setting much like the macro setting on an old Sears lens I picked up a while back. If I twist the ring from O to C, it bumps the aperture to 8.0 and won't allow me to drop back down to 6.3 without twisting back to C again.

All in all it seems to be a decent enough lens (for $8). My only test shots have been through a window at my birdfeeders on an overcast day.

As an aside, I need to see what the bokeh with this thing looks like - I counted when I was trying to see what the O<-->C ring did and it has 12 or 13 blades in there!

03-21-2011, 08:41 AM   #2
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That is most likely a Open Close ring for a pre-set lens. In the aperture ring you select the desired aperture. Then in that ring you move to the Open position for easier composition and focusing. When you are ready to shoot you move it to Close and it will close to the pre-set aperture value set before. Hence the name Pre-set lens. If you forget to close it, you'll shoot wide open regardless of aperture ring setting.
Hope this helps.

Thanks,
03-21-2011, 08:42 AM   #3
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Some lenses with pre-set aperture may have a ring to set the aperture and one to open or close the lens to the setting you have chosen. I would guess it means open or closed.
03-21-2011, 08:43 AM   #4
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Ha! you beat me to it!

03-21-2011, 08:47 AM   #5
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Hin's Tech Corner: Quantaray 400mm f/6.3 Test Shots/Review
03-21-2011, 09:06 AM   #6
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Thats the lens!

His review seems to be pretty spot on from what I've seen so far from mine. I was amazed how light this thing is considering its length.
03-21-2011, 09:07 AM   #7
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QuoteOriginally posted by Sagitta Quote
Thats the lens!

His review seems to be pretty spot on from what I've seen so far from mine. I was amazed how light this thing is considering its length.
That's because it's mostly an empty tube.
03-21-2011, 02:17 PM   #8
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QuoteOriginally posted by Sagitta Quote
I'm guessing Open/Closed? If I'm wrong could someone correct me, please?

I just bought a cheap ($8!) Quantaray 400mm lens which has some sort of screw mount adapter on it. It seems to work just fine on my K-x, except it has the mysterious O <--> C ring on it. The "C" setting only seems to work at the wide open 6.3 aperture setting much like the macro setting on an old Sears lens I picked up a while back. If I twist the ring from O to C, it bumps the aperture to 8.0 and won't allow me to drop back down to 6.3 without twisting back to C again.

All in all it seems to be a decent enough lens (for $8). My only test shots have been through a window at my birdfeeders on an overcast day.

As an aside, I need to see what the bokeh with this thing looks like - I counted when I was trying to see what the O<-->C ring did and it has 12 or 13 blades in there!
I have a copy of it's slow, dimwitted cousin, the Five Star 500mm which bears a strong family resemblance to the Quantaray. It has the preset aperture system as well but one stop slower at f8.
I was unaware of the 400mm. I will have to keep an open eye out for one for a friend.

03-21-2011, 10:39 PM   #9
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QuoteOriginally posted by Nowhere Matt Quote
I have a copy of it's slow, dimwitted cousin, the Five Star 500mm which bears a strong family resemblance to the Quantaray.
How dimwitted is that? I've seen a bunch of them for sale over time and was always curious about what images they can produce, but I couldn't find any samples.
03-22-2011, 09:16 AM   #10
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QuoteOriginally posted by Laurentiu Cristofor Quote
How dimwitted is that? I've seen a bunch of them for sale over time and was always curious about what images they can produce, but I couldn't find any samples.
Here is something I put together today for those interested in samples from the Five Star 500mm:
http://flickr.com/gp/11040431@N02/S1P49T

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/91519-sigma-50...tar-500mm.html

Five Star 500mm 1:8 Lens Reviews - Pentax Third-Party Lens Review Database
03-22-2011, 04:37 PM   #11
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I actually now own the Quantaray 400mm *and* 500mm, and the 500 came with a 2X teleconverter. I promptly moved the converter over from the 500 to the 400 and ran around all day with it that way - I completely forgot to even take any shots with the 500 while it was daylight out!

I may go out later and do some moonshots myself just to see how they stack up.

FWIW, the 500 seems a lot sloppier than the 400 - I think its a case of the 400 being taken much better care of before it landed in my mailbox.
03-22-2011, 11:14 PM   #12
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QuoteOriginally posted by Nowhere Matt Quote
Here is something I put together today for those interested in samples from the Five Star 500mm:
Thanks for the link. Doesn't look that dimwitted to me. Seems to be well worth $50.
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