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10-13-2011, 11:28 AM   #46
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QuoteOriginally posted by StigVidar Quote
I also received a message that this one, eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices is nearly 1mm thicker than the Kipon adapter and should therefore be without focus problems.
I got this RJ adapter too. However, I am not sure if I can really get a sharp picture out of the 6mm/1.2 Pentax CCTV lens. Anyone knows how to change the aperture of this lens? I am not sure if it's becuz of f/1.2 i can't get a sharp image, like when I use f/1.4 with my 50mm/1.4 lens on Q.

10-13-2011, 12:22 PM   #47
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QuoteOriginally posted by madoka Quote
I got this RJ adapter too. However, I am not sure if I can really get a sharp picture out of the 6mm/1.2 Pentax CCTV lens. Anyone knows how to change the aperture of this lens? I am not sure if it's becuz of f/1.2 i can't get a sharp image, like when I use f/1.4 with my 50mm/1.4 lens on Q.
You need to loosen the screws that stop the aperture ring. You need a very small screwdriver.
10-13-2011, 02:00 PM   #48
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The Rayqual C and D adapters are sold with additional shims (0.05mm and 0.1mm thick) to fine tune the lens flange to back distance.

mount adapter


Last edited by Mistral75; 10-13-2011 at 02:25 PM.
10-13-2011, 02:09 PM   #49
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And this is a spacer tube set for the C Mount :



Including the following :
* Length 0.5mm 1pcs
* Length 1mm 1pcs
* Length 5mm 2pcs
* Length 10mm 1pcs
* Length 20mm 1pcs
* Length 40mm 1pcs


The two thinner ones are definitely compulsory for this kind of kit :



The other will be usefull as macro extension tubes.


Last edited by Zygonyx; 10-13-2011 at 02:23 PM.
10-16-2011, 02:57 PM   #50
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@Zygonyx: you have a private message

@alii: sorry for being off topic.
10-16-2011, 03:06 PM   #51
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Can anyone report on any of the quality of the images they are seeing with their Pentax CCTV lenses? I have one but still waiting on the mount.
10-17-2011, 08:46 AM   #52
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Hello,
i will do it as soon as i have presentable examples. The fixed Cosmicar/Pentax 16mm seems rather promissing.

Last edited by Zygonyx; 10-17-2011 at 09:04 AM.
10-17-2011, 08:53 AM   #53
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I've got the 6mm F/1.2 Pentax lens. It's pretty soft wide open with low contrast. Stopped down a couple stops helps things a lot. But this is not a "megapixel lens" so the resolution is noticeably lower than then 8.5mm Prime that comes with the Q. I also have the Computar 5mm F/1.4. This is nice wide angle and focuses VERY close. Like 1cm. Again, resolution is kinda low and there is some barrel distortion. Look at the flickr Pentax Q group for some of my photos I shot with the Computar. My C-mount spacers should arrive today so I can actually use my Pentax 6mm without unscrewing it half way. I'll have more pics after that.

10-17-2011, 09:16 AM   #54
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Thanks everyone. I'm interested to see how the lens I have compares and if it has the same softness issues. The Pentax 8-48,, f/1 goes down to f/22 aperture which could help with some resolution issues. Will find out soon enough.
10-17-2011, 10:48 AM   #55
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QuoteOriginally posted by knightzerox Quote
Thanks everyone. I'm interested to see how the lens I have compares and if it has the same softness issues. The Pentax 8-48,, f/1 goes down to f/22 aperture which could help with some resolution issues. Will find out soon enough.
Do not forget that the Q's sensor is very small, hence diffraction will appear very early, from f/2.3 onwards, and will strongly limit sharpness from f/4.6 onwards.

See falconeye's messages for more details:

https://www.pentaxforums.com/forums/1631697-post1067.html
https://www.pentaxforums.com/forums/1632986-post1079.html
https://www.pentaxforums.com/forums/1641723-post66.html
https://www.pentaxforums.com/forums/1632986-post1079.html
https://www.pentaxforums.com/forums/1634097-post1098.html
10-17-2011, 11:11 AM   #56
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QuoteOriginally posted by Mistral75 Quote
Do not forget that the Q's sensor is very small, hence diffraction will appear very early, from f/2.3 onwards, and will strongly limit sharpness from f/4.6 onwards.

See falconeye's messages for more details:

https://www.pentaxforums.com/forums/1631697-post1067.html
https://www.pentaxforums.com/forums/1632986-post1079.html
https://www.pentaxforums.com/forums/1641723-post66.html
https://www.pentaxforums.com/forums/1632986-post1079.html
https://www.pentaxforums.com/forums/1634097-post1098.html
Thanks for the links. I knew diffraction could be a problem when stopping down pretty low, but wasn't completely sure.

This may be a silly question but aren't the sensor sizes in the CCTV's the same 1/2 inch sensor? Why would the provide f/22 on a CCTV camera if the lens diffraction would create such a problem at that size? Or is it that for CCTV, that loss of image quality isn't an issue.
10-17-2011, 12:31 PM   #57
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There are 1/2 inch sensors in some CCTV cameras but their resolution (pixel density) is much lower. Hence, the limiting factor is pixel density, not diffraction. Diffraction becomes a problem when the radius of the Airy disk (the "diffraction blotch"), which increases when one stops down, is bigger than 2 pixels. The Pentax Q has 1.55Ám pixels. With very fewer pixels on roughly the same area CCTV sensors are much less sensitive to diffraction limitations.

Besides, as you say, correct exposure (aperture being the only parameter) or depth of field can be more important for CCTV cameras than image sharpness.
10-17-2011, 02:40 PM   #58
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No-name Chinese C-mount and D-mount adapters for the Q have appeared on eBay. 28 USD each from Hong Kong sellers, free shipping and handling.
10-18-2011, 05:55 PM   #59
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I got my c-mount lens spacers from Edmund Optics. I ordered a 1.0mm and 1.25mm. I'm testing them with my Kipon C mount adapter and my Pentax 6mm F/1.2 lens. For reference, the distance markings on this lens are for 8", 1ft, 1.5ft and infinity.

With the 1.0mm, the lens focuses noticeably further than the distance scale. When focused about 15 feet away, it lines up with the 8" mark and it focuses well past infinity.
With the 1.25mm spacer, the lens JUST focuses at on distant objects when set to infinity. In fact, the DoF is pretty wide at F/2 when focused just short of infinity.

So I think the 1.25mm spacer is the one to get if that's the route you're taking.
10-18-2011, 06:27 PM   #60
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Thanks for the info. I'll order mine today, was planning on just going to hardware store for a spacer. Still waiting on adapter. Thinking I may have to just order another one from a different person.
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