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09-03-2017, 07:52 AM   #1
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Pentax 8-48mm f/1.0 c-mount lens removing auto iris mechanism

So I acquired a Pentax c-mount 8-48mm f/1.0 that has the auto iris mechanism. I was hoping to be able to remove the auto iris mechanism and that the standard manual lens would be underneath it. So far I don't have a screwdriver small enough or strong enough to remove the screws on the auto iris thing but does anyone know if this is just a mechanism that moves the aperture ring for you and underneath is the basic lens. Or is this mechanism more integrated into the lens and removing it would expose the lens innards?

09-03-2017, 07:53 AM   #2
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here's a photo of the lens
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09-03-2017, 02:43 PM   #3
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I have no experience with said lens, but my suspicion would be that it's not just a manual lens with the auto iris parts clamped around it. That being said, it my have been able in a non-auto version. If so, the modifications to make it support the auto iris may be easy to work around.
09-03-2017, 02:48 PM   #4
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I have a Cosmicar/Pentax (pic below) which appears to be identical except for the auto mechanism on yours. I doubt the manual mechanism could lie beneath your auto cover.







Last edited by PJ1; 09-03-2017 at 02:51 PM. Reason: clarification
09-03-2017, 06:40 PM   #5
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Ah ok. How is the lens? Do you use it on a Q?
09-03-2017, 11:23 PM - 1 Like   #6
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I had one of the auto-iris lenses. I dismantled the electronic housing (lots of cuts on fingers due to construction- it's well made) and found that there was no body to the rear of the lens. In order to use the lens (aperture always closed) I had to use rubber bands to control the aperture etc.IMVHO a lot of hard work for little reward.
09-04-2017, 07:35 AM   #7
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Thank you for your testimony. That's a big bummer. I guess I'll just sell it






QuoteOriginally posted by spinno Quote
I had one of the auto-iris lenses. I dismantled the electronic housing (lots of cuts on fingers due to construction- it's well made) and found that there was no body to the rear of the lens. In order to use the lens (aperture always closed) I had to use rubber bands to control the aperture etc.IMVHO a lot of hard work for little reward.
09-04-2017, 02:35 PM   #8
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QuoteOriginally posted by shaolen Quote
Do you use it on a Q?

I do. Next week I intend to give it a try in low-light rainforest next week. I have done comparison with the 06 lens at 45mm and the Cosmicar/Pentax at 48mm. It "glows" quite a bit wide open but I would give it the edge over the 06 at f5.6. See my thread Cosmicar/Pentax 8-48mm/f1.0-1.2 on the Q - PentaxForums.com
Check out the water droplets and the small protuberance on the stem in the two 100% crops.

09-04-2017, 05:02 PM   #9
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Oh thank you for that. I guest it figures that it would have that glow and be soft wide open. I imagine it will still be usable in video wide open though




QuoteOriginally posted by PJ1 Quote
I do. Next week I intend to give it a try in low-light rainforest next week. I have done comparison with the 06 lens at 45mm and the Cosmicar/Pentax at 48mm. It "glows" quite a bit wide open but I would give it the edge over the 06 at f5.6. See my thread Cosmicar/Pentax 8-48mm/f1.0-1.2 on the Q - PentaxForums.com
Check out the water droplets and the small protuberance on the stem in the two 100% crops.
09-04-2017, 05:43 PM   #10
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Those are great for SD video. Not that good for anything else unfortunately.
09-04-2017, 06:52 PM   #11
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QuoteOriginally posted by shaolen Quote
thank you for that

There is also some info in that thread from someone who built their own power mechanism for a similar lens.
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