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10-01-2012, 01:19 PM   #1
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Reverse Mounting my 50/1.2

Hello!

This is my first post on the site (although i have been creeping for a couple months) and I'm glad to be part of the Pentax nation.

Although my regular shooter is a Oly E-600, I also shoot a K110D a K1000 and until very recently an MX.

I recently purchased a mint SMC 50/1.2 and I was thinking about using it for reverse mounted macro.

My question is this:

If I reverse mount another lens, say my 28/2.8, to my 50/1.2, are there any adverse side effects? I'm assuming that the added weight of the 28 or even another 50mm would not be good on the barrel of the 50/1.2 in the long run for an old lens. Would this loosen the barrel or anything of that sort?

Any help on this topic would be very helpful as well as very much appreciated. Also if anyone knows a better lens combo for macro, I'm not against friendly advising

10-01-2012, 02:50 PM   #2
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I personally have not heard reverse mounting on lens onto the front of another. I only way I know of and have done is use an adapter that screws onto the filter threads on the front of the lens and the other side of the ring adapter is the K-mount to attach to the camera. You will have no auto control of the aperture so when you stop down it will reduce your light as you set your exposure. In other words, manual mode only.
10-01-2012, 02:59 PM   #3
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I'd be reluctant to reverse-mount my 50/1.2 out of fear of scratching the rear element. Also, it is a rather heavy lens, and for reverse mounting I'd rather use something more expendable such as an M50/1.7 (known to produce good results reversed on extension). I wouldn't be as worried about reversing a 28/2.8 onto the 50/1.2, though, unless your 28 is a lot heavier than mine. How much magnification are you trying to achieve?
10-01-2012, 03:33 PM   #4
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To get better macro quality you can reverse mount a lens, but you mount the reversed lens directly to the camera and not to the front of another lens.

If you look at old Pentax lens manuals you will find that the 28 and 35mm focal length lenses will give you better maginfication and quality than a 50mm f1.2.

To reverse mount a 50mm f1.2 you need a 52mm reverse adapter - 52mm filter thread on one side and K-mount on the other side.

You will have to meter and focus manually as there is no electronic or mechanical connection to the lens. Focus will be by moving the camera and lens backwards and forwards. The focus mechanism of the lens no longer works as it is fixed to the camera. Some focus distances can get quite small. One to two inches (25 to 50mm) is not unusual.

In order to provide a bit of a lens hood and to protect the now exposed rear element of the reversed lens, wind the focus of the lens to the closest distance to extend the lens. This will now cover the rear element.

The magnifications with a reversed lens is usually greater than 1:1 with magnifications likely to be in the range of 2:1 to 4:1. Which is 2 to 4 times larger than real life.

You can also go further and reverse a lens with extension tubes between the camera and the reversed lens for even more magnification. See the extension tube manuals for further details.

Regards

Chris Stone

10-01-2012, 07:08 PM   #5
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QuoteOriginally posted by baro-nite Quote
I'd be reluctant to reverse-mount my 50/1.2 out of fear of scratching the rear element. Also, it is a rather heavy lens, and for reverse mounting I'd rather use something more expendable such as an M50/1.7 (known to produce good results reversed on extension). I wouldn't be as worried about reversing a 28/2.8 onto the 50/1.2, though, unless your 28 is a lot heavier than mine. How much magnification are you trying to achieve?
I'm basically seeing what the most i can get out of my current lenses and go from there. I may have to invest in a 1.7 it seems. Do you think a 50/2 would suffice? My main concern is adding unnecessary stress to an already old lens, one that I would like to keep in good condition if possible. If reverse mounting another lens to the 1.2 adds a significant amount the lens body and the mechanics, then the 1.2 is out of the picture.

QuoteOriginally posted by seventhdr Quote
To get better macro quality you can reverse mount a lens, but you mount the reversed lens directly to the camera and not to the front of another lens.

If you look at old Pentax lens manuals you will find that the 28 and 35mm focal length lenses will give you better maginfication and quality than a 50mm f1.2.

To reverse mount a 50mm f1.2 you need a 52mm reverse adapter - 52mm filter thread on one side and K-mount on the other side.

You will have to meter and focus manually as there is no electronic or mechanical connection to the lens. Focus will be by moving the camera and lens backwards and forwards. The focus mechanism of the lens no longer works as it is fixed to the camera. Some focus distances can get quite small. One to two inches (25 to 50mm) is not unusual.

In order to provide a bit of a lens hood and to protect the now exposed rear element of the reversed lens, wind the focus of the lens to the closest distance to extend the lens. This will now cover the rear element.

The magnifications with a reversed lens is usually greater than 1:1 with magnifications likely to be in the range of 2:1 to 4:1. Which is 2 to 4 times larger than real life.

You can also go further and reverse a lens with extension tubes between the camera and the reversed lens for even more magnification. See the extension tube manuals for further details.

Regards

Chris Stone
After doing a couple tests on my Oly, I came to the conclusion that reverse mounting a lens on another lens that is mounted to the body of the camera will produce an even higher amount of magnification than a single reversed lens. Here's my evidence but i assume its different for every lens so my findings are less than conclusive. Thanks for the posts so far!

Zuiko 40-150mm @150mm
Name:  150mm.jpg
Views: 420
Size:  159.0 KB

Reversed SMC 50/2
Name:  50mm.jpg
Views: 387
Size:  86.9 KB

Zuiko @150mm + SMC 50/2 reversed
Name:  150mm50mm.jpg
Views: 460
Size:  138.7 KB

Sorry for the crap quality, I don't have most of my gear with me.

Is this the norm with reversing lenses?
10-01-2012, 08:40 PM   #6
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Also, Reverse lens photos were taken by holding the lens onto the body or the other lens. Perhaps this accounts for some magnification difference.
10-01-2012, 08:47 PM - 1 Like   #7
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I have the vaguest of memories that the 50mm f1.2 is built differently than other 50s, but that series of lenses is really overbuilt. I think the worst thing that could happen is that some screws are already loose, and extra stress will loosen the rest. That shouldn't result in anything fatal, just tightening the screws again. Here's a photo of the M50/1.7 partly disassembled. The ring with the filter threads attaches with three screws that go in the empty holes. Maybe the 1.2 uses a different attachment but likely just as strong.



I'd share the worries about the rear element but the 50/1.2 is mounted normally on the camera, with a 28 hanging off it. Cut the center out of a spare lens cap and glue on a rubber hood to protect the 28mm rear element and help with flare. With this level of magnification, it's easy to bonk the assembly into the subject while you're setting up the shot.

I have no idea whether there's any advantage to using a super-fast lens for this. If not, dedicating a cheaper lens to that setup would save time and worry.
10-02-2012, 04:37 AM - 1 Like   #8
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QuoteOriginally posted by J.Langer Quote
I came to the conclusion that reverse mounting a lens on another lens that is mounted to the body of the camera will produce an even higher amount of magnification than a single reversed lens.
With a lens mounted normally (the primary), reverse-mounting a lens to the front of it (the secondary) gives you a magnification equal to the ratio of the two focal lengths. So reverse-mounting a 28 onto a 50 gives you about 1.8:1 magnification. That is, a 10mm object will produce an 18mm image on the sensor.

Reversing a lens directly onto the camera doesn't produce so much magnification unless you add extension (with a bellows or with extension tubes).

10-02-2012, 10:40 AM   #9
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Much thanks to all who have posted!

I will test the 50/1.2 vs 50/2 to see if there is any IQ difference or difference at all for that matter. Glad that not much damage will come from reverse mounting onto the 1.2. I will try making a lens cap-hood aswell.Thanks for the info Dave!

QuoteOriginally posted by baro-nite Quote
With a lens mounted normally (the primary), reverse-mounting a lens to the front of it (the secondary) gives you a magnification equal to the ratio of the two focal lengths. So reverse-mounting a 28 onto a 50 gives you about 1.8:1 magnification. That is, a 10mm object will produce an 18mm image on the sensor. Reversing a lens directly onto the camera doesn't produce so much magnification unless you add extension (with a bellows or with extension tubes).

I think I've got it! So for highest magnification possible, would it be more sensible to use say a Takumar A 70-200mm @ 200 with the 28mm reversed on it?
If you know of any better lens combos it would be much appriciated, my k-mount lenses are as follows; SMC Pentax K 50/1.2, SMC Pentax K 50/2, SMC Pentax M 28/2.8, SMC Pentax M 28/3.5, Takumar A 70-200/4, Vivtar MC 80-200/4.5, although I'm also in the market for either a Vivitar 55mm F2.8 1:1 macro or Vivitar 90mm f2.8 Macro
10-02-2012, 11:11 AM   #10
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A lens when mounted in reverse (actually, it doesn't need to be reversed, but it's difficult to mount non-reversed) in front of another lens acts as a magnifier. It's the same concept as a "close-up" lens (e.g. Raynox DCR-250). The strength of the magnification is 1/focal length of the lens in meter. For a 50mm lens, it's 20 diopters (Raynox DCR-250 is 8 diopters).

To protect the end of the reversed lens, use a rear lens cap with the bottom removed (you can just grind the bottom off).
10-02-2012, 11:34 AM   #11
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QuoteOriginally posted by J.Langer Quote
So for highest magnification possible, would it be more sensible to use say a Takumar A 70-200mm @ 200 with the 28mm reversed on it?
I've only done a few experiments with stacked lenses; check out https://www.pentaxforums.com/forums/lens-clubs/143202-macro-any-means-necessary-club.html. One thing I have found is that with a zoom as the primary, you get vignetting pretty quickly if you zoom out (away from the longest FL). Try it, but you might find that with the 70-200 you have to use it at or near 200 to avoid vignetting, and 7:1 magnification is pretty extreme -- hard to deal with.
10-02-2012, 12:09 PM   #12
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QuoteOriginally posted by baro-nite Quote
I've only done a few experiments with stacked lenses; check out Macro by any means necessary club. One thing I have found is that with a zoom as the primary, you get vignetting pretty quickly if you zoom out (away from the longest FL). Try it, but you might find that with the 70-200 you have to use it at or near 200 to avoid vignetting, and 7:1 magnification is pretty extreme -- hard to deal with.
Thanks much for the help and the link, I'll check it out. I did notice some vignetting lower telephoto lengths, and at 70mm it was more like a peep hole than anything else. the 7:1 magnification will mostly be used for my attempts at some insect portraits after being amazed by this thread. https://www.pentaxforums.com/forums/post-your-photos/51505-macro-my-macro-photos.html i decided i would make an attempt at it. Plus my friend operates a Insectarium in my home province so there will be many attempts made. Thanks all!
10-02-2012, 08:43 PM   #13
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Back in the 60s we would reverse mount a 50 on bellows, with the theory that the lens was corrected for best image close to the rear element and farther from the front, so on bellows with the lens extended from the camera you wanted the lens reversed compared to normal use.
For bellows and closeup use we usually found simpler and slower lenses better than fast lenses, which are nor formulated with this use in mind. The bellows mount lenses from camera makers would usually be f3.5 to f2.8, simpler 4 or 5 element designs, and they gave great results for macro work. I still use a 60 f2.8 Elmar on my Leica M9 with bellows.
I used a 55 f2.0 Super Takumar on bellows a lot. I'd suspect the f1.7 or even the 50 f2.0 would be better than the 50 f1.2 for this work. (I've had many 50 f1.7, 1.4, and 1.2 lenses, and have found the 1.7 to be the best overall of Pentax lenses.)
10-02-2012, 11:28 PM   #14
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QuoteOriginally posted by TomB_tx Quote
Back in the 60s we would reverse mount a 50 on bellows, with the theory that the lens was corrected for best image close to the rear element and farther from the front, so on bellows with the lens extended from the camera you wanted the lens reversed compared to normal use.
For bellows and closeup use we usually found simpler and slower lenses better than fast lenses, which are nor formulated with this use in mind. The bellows mount lenses from camera makers would usually be f3.5 to f2.8, simpler 4 or 5 element designs, and they gave great results for macro work. I still use a 60 f2.8 Elmar on my Leica M9 with bellows.
I used a 55 f2.0 Super Takumar on bellows a lot. I'd suspect the f1.7 or even the 50 f2.0 would be better than the 50 f1.2 for this work. (I've had many 50 f1.7, 1.4, and 1.2 lenses, and have found the 1.7 to be the best overall of Pentax lenses.)
I've heard the same thing, though if I am to use the 50/1.2 i would mount it traditionally, with another lens, perhaps a 50/2 or 28/2.8 depending on the subject and magnification needed. I seem to recall reading somewhere that opening the base lens as wide as possible on a two lens outfit is advisable, so I was assuming that the extra light guzzling ability of the 1.2 would be better for lower ISO. It occurs to me now that I may have forgotten to say that I will be using this set-up on film, ektar 100 to be exact, so any extra light would be optimum.
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