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06-27-2013, 08:01 AM   #16
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QuoteOriginally posted by Not a Number Quote
How about pinhole lenses?
They don't even have a single element!

06-27-2013, 09:08 AM   #17
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The mount cover lens on Q is the only one like that from pentax
06-27-2013, 09:32 AM   #18
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Holga "pinhole" lenses have a plastic lens:

HOLGA HL-P Lens for PENTAX DSLR SLR K-5 K-r K-x K-m K-7 K20D K110D LOMO | eBay
06-27-2013, 09:48 AM   #19
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QuoteOriginally posted by Not a Number Quote
According to its "specifiation" (sic!),
that's an optical lens that needs focusing, not a pinhole.

06-27-2013, 04:45 PM   #20
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My bad. However the Holga HL-P has only a single element.
06-27-2013, 06:23 PM   #21
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QuoteOriginally posted by Not a Number Quote
However the Holga HL-P has only a single element.
Right, it certainly answers OP's question.
06-28-2013, 06:39 AM   #22
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konstruktor DIY kit from lomography it lens got 1 element you can screw it into your K mount with M42 adapter
06-28-2013, 08:03 AM   #23
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QuoteOriginally posted by ignmar Quote
konstruktor DIY kit from lomography it lens got 1 element you can screw it into your K mount with M42 adapter
Well.. I am building my own single element lens! I had a cheap Kalimar, whose mount was not compatible with Pentax. I am using its front element and the helicoid mechanism to build my own manual focus lens with no aperture control (always wide open). Looks like the results are almost as expected but due to lack of a proper camera mount, it is a little hard to use. I am trying to figure out how to attach a K-mount!

06-28-2013, 08:20 AM   #24
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There are many meniscus, body cap and pin-hole type lenses out there, don't know if you would count them as "single element" and don't know if they actually are just a hole or if they have some kind of lens in there. And some might need adapters. But I don't have any list on hand and Adam is the authority on actual Pentax brand stuff
06-28-2013, 08:24 AM   #25
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QuoteOriginally posted by TropicalMonkey Quote
Well.. I am building my own single element lens! I had a cheap Kalimar, whose mount was not compatible with Pentax. I am using its front element and the helicoid mechanism to build my own manual focus lens with no aperture control (always wide open). Looks like the results are almost as expected but due to lack of a proper camera mount, it is a little hard to use. I am trying to figure out how to attach a K-mount!
if you need just a mount that quite easy just buy a cheap body cap and cut out the middle piece then glue it with hot glue there will be fit just fine.
06-28-2013, 08:43 AM   #26
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QuoteOriginally posted by ignmar Quote
if you need just a mount that quite easy just buy a cheap body cap and cut out the middle piece then glue it with hot glue there will be fit just fine.
Very good idea! I have several body-caps lying around.
06-28-2013, 08:46 AM   #27
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Not entirely irrelevant to this thread...

..a Fraunhofer achromatic doublet (two elements in one group) brings red and blue light to the same focus.
500mm FL f/5 at about 80 feet and 30 feet as I recall. Generally the fewer the elements the better the contrast all else being equal but it sometimes can take a lot of PP to get a achromat file to look right.
This scope cost 100 bucks new.

Last edited by wildman; 07-29-2013 at 04:23 AM.
06-28-2013, 09:20 AM   #28
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Wow! Nice shots!!!

QuoteOriginally posted by wildman Quote
Generally the fewer the elements the better the contrast all else being equal
Minimal (or lack of) internal reflections and minimum number of elements in the "signal" path.

QuoteOriginally posted by wildman Quote
but it sometimes can take a lot of PP to get a achromat file to look right
Can you explain that, please?

Edit: I can't stop looking at those images! Did you do any post-processing at all?

BTW, what lens/scope is that?

Last edited by TropicalMonkey; 06-28-2013 at 09:25 AM.
06-28-2013, 09:45 AM   #29
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QuoteOriginally posted by TropicalMonkey Quote
Well.. I am building my own single element lens! I had a cheap Kalimar, whose mount was not compatible with Pentax. I am using its front element and the helicoid mechanism to build my own manual focus lens with no aperture control (always wide open). Looks like the results are almost as expected but due to lack of a proper camera mount, it is a little hard to use. I am trying to figure out how to attach a K-mount!
Inspired by this thread, I did something like that yesterday with the front element of a fungus-infected JCPenney zoom. I just used toilet paper tubes and tape. You can see the results here:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/229186-tp-special.html

One sample:

06-28-2013, 09:59 AM   #30
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Is that the reason to have more than one lens -- to focus both ends of the spectrum to the same point? The lens material has to be different on those two lenses then.
I also took several shots but all indoor, so I didn't notice the chromatic abberation, it all looked "dreamy"!!
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