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05-21-2019, 10:06 PM - 2 Likes   #1
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Pentax Q mount macro reverse rings

In short: inexpensive, uncomplicated and performs a neat trick worthy of the small space it will occupy in any Q owners arsenal useful accessories.


All metal one piece construction with a 40.5mm filter thread. Letís you reverse mount a lens via its front filter thread onto a Q body for macro photography/video.

40.5mm is common for most of the Pentax Q system lenses but this adapter has no electrical contacts so forget focus/aperture control by wire. However with super macro, I focus more often by adjusting the distance from the object so not a deal breaker. We are 100% fine with lenses that have mechanical aperture/ focus. Perhaps by design or just coincidence, 40.5mm is the most common filter thread amongst my own collection of C-mount lenses. Tried on Pentax/Cosmicar 8.5mm, 12mm, which themselves are physically pretty compact. Is this why Pentax chose this size for filters so as to have compatibility with existing c mount lenses?

If you have lenses with other front filter thread sizes, it is not hard to add a simple step up or down ring to suit.

Depending on the lens, the levels of magnification can be something akin to turning the Q into a microscope. This is a close look at the white A printed on the side of a C mount lens. Appears like a moonscape! Certainly exceeding 1:1 macro, though can someone to chip in to work out what level of magnification this is? Pointing at a ruler shows 2mm fills the width of the original Qís frame with a reversed Cosmicar 8.5mm f1.5.





With the reversed Pentax 02 zoom at 5mm focal length the view is roughly 1.3mm!


I have have a generic set of 40.5mm macro filter lenses to compare with and although itís nice to have some autofocus macro on Pentax Q system lenses, stacking filters adds so much glass that there is noticeable contrast loss. The levels of magnification are not as impressive either. Maybe my set of macro filters are too cheap though.
There is a Fotodiox branded 52mm macro reverse ring that should do a similar job

Fotodiox Macro Reverse Ring - 52mm Filter Thread for Pentax Q Mirrorless Camera amazon.com : Fotodiox Macro Reverse Ring - 52mm Filter Thread for Pentax Q Mirrorless Camera : Flash Adapter Rings : Camera & Photo?tag=pentaxforums-20&

but this unbranded 40.5mm version I bought from Toaboa myself costs less and is more of a match for my C mounts.

Anyone already using reverse macro ring on Pentax Q?


Last edited by 2old4toys; 05-21-2019 at 10:12 PM.
05-22-2019, 09:04 AM - 1 Like   #2
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Very cool! I have the Q->52mm adapter, very similar. Didn't know a 40.5mm existed!
I think I found it on Taobao:
Lens Accessory Pentax Q Lens Reverse Loop PENTAX Q-40.5MM Reverse Loop Reverse Loop Microring

How much did you pay for shipping?

---------- Post added 05-22-19 at 12:17 PM ----------

also of interest on Taobao might be this Q cap set:
https://item.taobao.com/item.htm?id=542464475188

hard to find, these look just like Pentax original and cheap!
the rear Q lens cap is superior to the common flat type imo, stays on lens or adapter better!
05-22-2019, 05:46 PM   #3
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QuoteOriginally posted by kayakfari Quote
Very cool! I have the Q->52mm adapter, very similar. Didn't know a 40.5mm existed!
I think I found it on Taobao:
Lens Accessory Pentax Q Lens Reverse Loop PENTAX Q-40.5MM Reverse Loop Reverse Loop Microring

How much did you pay for shipping?

---------- Post added 05-22-19 at 12:17 PM ----------

also of interest on Taobao might be this Q cap set:
https://item.taobao.com/item.htm?id=542464475188

hard to find, these look just like Pentax original and cheap!
the rear Q lens cap is superior to the common flat type imo, stays on lens or adapter better!
Yes, that looks like the same seller of this 40.5mm macro ring, so thanks for the Toaboa link! My #3 wide flange c adaptor was also from Toaboa site but I thought it would be easier for most people here to shop from an eBay link instead. I am living in Hong Kong so postage from mainland China is hardly anything for me. I will add a set of those PQ push on rear lens and body caps to my basket. Report back after I get them.

Last edited by 2old4toys; 05-22-2019 at 05:53 PM.
05-23-2019, 07:34 AM   #4
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Shipping to the States is pretty steep from their estimates. Too bad, the prices are good on Taobao.

05-23-2019, 09:29 AM   #5
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QuoteOriginally posted by 2old4toys Quote
40.5mm is common for most of the Pentax Q system lenses but this adapter has no electrical contacts so forget focus/aperture control by wire. However with super macro, I focus more often by adjusting the distance from the object so not a deal breaker.
Is the aperture closed down to minimum (for Q native lenses)?
05-24-2019, 07:57 AM   #6
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QuoteOriginally posted by kwb Quote
Is the aperture closed down to minimum (for Q native lenses)?
I expect itís wide open for the native lenses.
05-24-2019, 08:35 AM   #7
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Aren't the 01, 02, etc native Q system lenses always closed by default since they have the leaf shutters inside?

I haven't tried using these reversed myself, but recall reading that one has to dismount the lens with cam ON so they stay open?
05-24-2019, 10:56 AM   #8
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QuoteOriginally posted by 2old4toys Quote
I expect it’s wide open for the native lenses.
Thanks, I thought that all native lenses close down the aperture when removed from the camera, so I quickly checked and it seems like it's the leaf shutter that closes. Below is what I found with my Q7 and Q native lenses.
  1. Mount 01, 02, 06 or 08 lens on Q7 (not reverse-mount, just mount as usual) and turn it on. When I turn it off, the leaf shutter is closed right away. It doesn't open when I remove the lens from the body. Cannot tell about the aperture because no light passes through.
  2. Turn on the camera and unmount the lens without powering the camera off. The shutter and the aperture stay open.
If I reverse mount any of these lenses, unless I remove the lens from the body while it's still powered, I cannot take any picture (OK, I can take black one ). Since apparently this is not the case with you, 2old4toys, could this be model-dependent? Maybe there's a difference between Q and Q7?

BTW the behavior on Q7 is like the opposite of Canon DSLRs where the lens stays wide-open unless you remove the lens from the body without turning it off.

Added later:

QuoteOriginally posted by kayakfari Quote
Aren't the 01, 02, etc native Q system lenses always closed by default since they have the leaf shutters inside?

I haven't tried using these reversed myself, but recall reading that one has to dismount the lens with cam ON so they stay open?
Oh I saw your post after I posted mine, you beat me on this one kayakfari!

05-24-2019, 04:51 PM   #9
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Yup, dismount while the leaf shutter is open, but I donít think you can set the aperture this way.
05-24-2019, 06:01 PM   #10
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Ah, so the shutter could be open or closed depending on how you unmount, but aperture is wide open no matter what, now I understand.

I confirmed by removing 01 lens while the body was powered with F/1.9 at first and then with F/8. Thank you very much 2old4toys!
05-25-2019, 07:11 AM - 1 Like   #11
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QuoteOriginally posted by kwb Quote
Is the aperture closed down to minimum (for Q native lenses)?
Figured it out if you really want smaller aperture with a reverse mount native Q lens, itís doable. In manual mode, set the desired aperture and a 30 second exposure... gives you plenty of time to dismount a native lens while the shutter is open.

F8 is smallest they go to though.

Reverse C Mount lenses typically let you go way beyond F8 if you want it to.

Side note: I have just tried all the native lenses with 40.5mm filter thread reverse mounted and the 02 at 5mm offers the greatest magnification.
10-02-2019, 11:56 AM   #12
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I wish I could find a reverse mount to fit my Pentax 16mm c-mount lens. If this exists please let me know
10-02-2019, 12:40 PM - 2 Likes   #13
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QuoteOriginally posted by shaolen Quote
I wish I could find a reverse mount to fit my Pentax 16mm c-mount lens. If this exists please let me know
If it's this one,
Pentax C31630KP 2/3" C Mount 16mm f/1.4 Lens C31630KP
the spec says filter size is 27mm.

I guess you could use the 40.5mm to Q reverse mount ring that 2oldfortoys posted about, together with a step UP (not DOWN) ring from 27mm to 40.5mm. For the latter, you could combine 27 to 37mm step up ring and 37 to 40.5mm step up ring, for example.
10-02-2019, 01:14 PM   #14
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QuoteOriginally posted by kwb Quote
If it's this one,
Pentax C31630KP 2/3" C Mount 16mm f/1.4 Lens C31630KP
the spec says filter size is 27mm.

I guess you could use the 40.5mm to Q reverse mount ring that 2oldfortoys posted about, together with a step UP (not DOWN) ring from 27mm to 40.5mm. For the latter, you could combine 27 to 37mm step up ring and 37 to 40.5mm step up ring, for example.

Wow that's great thinking! Thank you
01-21-2020, 06:15 PM - 3 Likes   #15
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I just discovered this thread. Cool item! I'm not a Q body shooter, but I've reversed a Q 03 fish-eye. Even though it lacks filter threads, I managed to mount it on my KP using a 37-49 step-up ring and a K-mount 49mm reverse adapter. I put a bit of masking tape around the front of the lens barrel for a snug fit in the 37mm end of the stepping ring.



There might be a combination of stepping rings that would let you mount it on a Q body using the Q mount reverse adapter which is the subject of this thread. No lens shutter or aperture to worry about, either.

I was pleasantly suprised with the results. This is a close-up of half-tone printing on a laser printed price tag:




I've put up a thread here on the Q forum here: Reversed 03 fish-eye on KP - PentaxForums.com

Last edited by Thagomizer; 01-21-2020 at 06:25 PM.
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