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09-26-2020, 11:09 AM   #1
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Reverse Mounting Ring.

Hello all, can somebody please advise me to the best Reverse Mounting Rings for the Pentax K100D Super please ??
I currently have the " Cosina 50mm F1.8 manual focus " and " SMC Pentax - DA 18-55mm F3.5 / 5.6 AL Auto focus " lenses that i would like to try for Macro photos, so any advice will be appreciated.

thank you.

09-26-2020, 11:35 AM   #2
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According the lens database the Cosina has a 49mm filter thread and the Pentax a 52mm filter size.

Assuming you want to stack the two lenses nose-to-nose as it were you would want a 49mm to 52mm reverse ring. Brand shouldn't matter much. Odds are they are made by the same one or two manufacturers. I don't know your best source for rings of this type in the UK or EU.
09-26-2020, 01:04 PM   #3
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QuoteOriginally posted by Wolfestone Quote
Hello all, can somebody please advise me to the best Reverse Mounting Rings for the Pentax K100D Super please ??
I currently have the " Cosina 50mm F1.8 manual focus " and " SMC Pentax - DA 18-55mm F3.5 / 5.6 AL Auto focus " lenses that i would like to try for Macro photos, so any advice will be appreciated.

thank you.
The da lens will be harder to manage as the aperture isn't controlled by a manual ring. The lens will have no control over aperture - it will be fully closed if memory serves me.

If wide open is ok or you are willing to tinker until you get the aperture roughly where you want it, you can wedge a bit of paper in the slot by the aperture lever on the lens and it will stay put fixing the aperture in one place temporarily.

Last edited by UncleVanya; 09-26-2020 at 07:52 PM.
09-27-2020, 12:31 AM   #4
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QuoteOriginally posted by Not a Number Quote
According the lens database the Cosina has a 49mm filter thread and the Pentax a 52mm filter size.

Assuming you want to stack the two lenses nose-to-nose as it were you would want a 49mm to 52mm reverse ring. Brand shouldn't matter much. Odds are they are made by the same one or two manufacturers. I don't know your best source for rings of this type in the UK or EU.
Hello again, thank you for your answer, it was not my intention to stack up the 2 lenses together, i was hoping to use either ( or both ) seperately.

thank you.

09-27-2020, 01:23 AM   #5
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QuoteOriginally posted by Wolfestone Quote
Hello again, thank you for your answer, it was not my intention to stack up the 2 lenses together, i was hoping to use either ( or both ) seperately.

thank you.
If you search on eBay for "pentax reverse" (no quotes) you'll find what you need. A Pentax-branded original might be considered the "best", but my after-market clone has served me well for many years and was much cheaper
Fiddling with the aperture mechanism on your 18-55mm will get boring very quickly!
Any older lens with a 49mm filter size and an aperture ring (it doesn't even need to be K-mount when used in reverse) will suit your purpose … adding a couple of filter-thread stepping rings to your collection can widen your opportunities and complete the system

Good luck … and enjoy
09-27-2020, 07:22 AM   #6
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I agree that most reversing rings offer identical performance. I have three or four and some adapter rings to allow them to work on 49 and 52mm easily. However reversing rings aren't very easy to use compared with something like the add on raynox lenses or a dedicated macro lens.
09-27-2020, 07:56 AM   #7
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QuoteOriginally posted by Wolfestone Quote
Hello again, thank you for your answer, it was not my intention to stack up the 2 lenses together, i was hoping to use either ( or both ) seperately.
Ok, then you want a K-mount reverse adapter. These usually come in 52 or 49mm. So either you have to buy one adapter for each filter size or use a step up/down ring. As noted before the DA lens does not have an aperture ring. One possible solution is to find a mirrorless K-mount adapter with an aperture ring and use this to control the diaphragm. It would act a sort of a lens hood on the mount end of the lens when reveresed.
09-27-2020, 09:29 AM   #8
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There are two approaches, a reversed single lens, and I would most likely go with the Cosina (although I might consider a different lens.

The other way is to use one lens forward and then with an adapter that screws into two lens at the same time, reversing one, is another approach.

Both techniques work, BUT with the single reversed lens you will be getting very close to your subject and you focus by moving the camera back and forth, not easy, but you will get high mag. Lighting can also be an issue.

The two lens approach (stacked lenses) really only works if you have two lenses with the same size filter (to the best of my knowledge). It is easier to focus than the single reversed lens, but is a challenge too, and maybe not super sharp.

I would recommend picking up one of John Shaw's older Nature books, one is "The Nature Photographer's Complete Guide to Professional Field Techniques" A lot of really great info in this book even if it was made in the the film era. He talks a lot about stacked lenses

09-27-2020, 09:54 AM   #9
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I've acheived good results with a reversed DA 18-55 II lens. The flexibility in magnification range that the zoom offers is quite handy. Tricky to use, but it's an easy way to go beyond 1:1 using a lens you've already got.

Not too long ago I started to use a Fotodiox lens adapter to control the diaphragm on lenses lacking an aperture ring. Beats trying to jam something next to the diaphragm control tab to keep the aperture open.

Last edited by Thagomizer; 09-27-2020 at 10:05 AM.
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