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03-05-2011, 11:46 PM   #1
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reversed lens?

Hi all,

Now that I have had my Kx (and 1st DSLR) for a while I feel like trying new things.

I have seen people talking about reversed lenses to get macro shots. I have a 18-55mm and a 55-300mm (kit lenses) plus a M 50mm f1.7 . Is there any cheap combination of lenses + adapters / extension tubes that may serve for this purpose at all?
I am not looking for anything fancy, just an alternative to expensive macro lenses to experiment with...

Thanks beforehand,
S

03-06-2011, 01:00 AM   #2
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You can only use a lens in reverse if it has an aperture ring. Otherwise you will have only one f stop. Your M 50 1.7 can do it. The reverse adapter screws on the front of the lens like a filter and the other end of the adapter is a simple lens mount. The adapter is very narrow, just enough to mate your lens backwards to the camera body. Can't help you on the cost. I bought mine abut 30 years ago. It must have been cheap because I didn't have much money then.
03-06-2011, 01:16 AM   #3
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Reversing rings are very cheap. Have a look on eBay. The above description is good and it won't take you long to see its virtues. Just remember to get extension tubes long enough to get the magnification you're after.
03-06-2011, 04:17 AM - 1 Like   #4
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Reversing the kit lens works too. You can gain control over the aperture by holding the lever in place - a short piece of tubing works well for this.


Its advantage over the M 50 reversed is that you'll have a range of magnifications available. The photo strips above are shots of my laptop's LCD screen to give an example of magnification and quality.

03-06-2011, 04:30 AM   #5
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There are two ways of using reversed lenses, using what you have.

1) With a cheap mount-reversal ring. For your M50, this would have a 49mm male thread on one side and a PK bayonet on the other. Reversing the lens gives you edge-to-edge sharpness but no magnification. For magnification, you need PK macro extension tubes. The lens on 50mm of tubes will have 1x magnification. The ring should cost ~US$5; the tubes should be ~US$10, shipped. Or you could use a 52mm-PK adapter for the 18-55, but I find that reversing that short kit lens is clumsy.

2) With a thread-reversal ring, to reverse-stack the M50.. Mounting on the 18-55 won't give much magnification; mounting on the 55-300 WILL! For the 55-300, you will need a ring with a 49mm male thread on one side and a 58mm male thread on the other side. It should cost ~US$5. The zoom is the PRIMARY; keep the aperture wide open. The M50 is the SECONDARY; control exposure and DOF with its aperture ring. Magnification is the ratio PRIMARY / SECONDARY so with the zoom at 300mm you'd get 300/50= 6x magnification! Whew!

With either reversal method, your working distance is VERY CLOSE, under two inches -- right around 45.5mm. And magnification eats light. It's not so bad at 1x, only a loss of 2 stops. At 6x you lose 7 stops! So tripod and/or controlled light is mandatory. Have fun!
03-06-2011, 06:47 AM   #6
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QuoteOriginally posted by RioRico Quote
.......
With either reversal method, your working distance is VERY CLOSE, under two inches -- right around 45.5mm.....
The 18-55mm kit lens reversed directly to the camera gives a working distance of about 126mm (5") at 55mm and magnification of about .6x. The 45.5mm limit does not appear until the lens is zoomed out to 18mm. See my posting above https://www.pentaxforums.com/forums/1415344-post4.html .

Last edited by newarts; 03-06-2011 at 06:57 AM.
03-06-2011, 06:54 AM   #7
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QuoteQuote:
....For your M50, this would have a 49mm male thread on one side and a PK bayonet on the other. Reversing the lens gives you edge-to-edge sharpness but no magnification....
You will have some magnification or demagnification depending on the details of lens construction (how deep the lens is recessed from the filter ring). It is easy to find out. Just hold the lens backwards in front of the camera mount while looking through the viewfinder. Look at a laptop screen and move the camera in & out until you see a focused image.

Extension tubes are more versatile than simply reversing the M 50 as they'll give a range of magnifications, while the reversed lens will have essentially a single magnification. Further the extension tubes will be useful for future lenses. Bellows might be even better, but they cost more than simple tubes.

Last edited by newarts; 03-06-2011 at 12:03 PM.
03-06-2011, 11:13 AM   #8
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wow, thanks for all the answers guys
I will explore the possibilities and bother you with more questions

03-06-2011, 03:41 PM   #9
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One more idea is to get a cheap and nasty K mount auto teleconverter and take the lens out to make and extension tube to give you a decent magnification with your 50mm 1.7.

David
03-06-2011, 07:46 PM   #10
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QuoteOriginally posted by newarts Quote
The 18-55mm kit lens reversed directly to the camera gives a working distance of about 126mm (5") at 55mm and magnification of about .6x. The 45.5mm limit does not appear until the lens is zoomed out to 18mm.
I stand corrected on kit-lens reversal working distance. Thanks for clearing that up.

[/me considers auto-trephination]

QuoteOriginally posted by newarts Quote
You will have some magnification or demagnification depending on the details of lens construction (how deep the lens is recessed from the filter ring).
I should have clarified that, but I was being succinct (brief). Simple reversal does not magnify; extension magnifies. Mount-reversing a lens with a deep inset gives some bit of extension, and thus *some* magnification. Control the extension (via tubes and/or bellows) to control the magnification.
03-06-2011, 08:38 PM   #11
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Could you let me know about any adapter or extension tubes you have had a good experience with?
thanks again,
S
03-07-2011, 08:11 AM   #12
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QuoteOriginally posted by sergysergy Quote
Could you let me know about any adapter or extension tubes you have had a good experience with?
thanks again,
S
I had a Kenko auto focus extension tube for a while, worked very well. I used it between the camera and the kit lens. Auto focus on the flower and tweak the focus with quick shift, easy and fast. I sold it when I got a macro lens. You could make one by using an auto focus teleconverter and removing the glass.
03-07-2011, 09:11 AM   #13
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QuoteOriginally posted by RioRico Quote
I stand corrected on kit-lens reversal working distance. Thanks for clearing that up...................
I'm not sure of what's going on, but it is what I observed experimentally. Likely it is a result of the spacing between the front principal plane and the sensor. The working distance also likely varies with the focusing control for a particular "focal length" because there may be internal focusing going on.

Let's think it through; it'd be nice to understand what's going on!

Dave
03-07-2011, 11:06 AM   #14
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QuoteOriginally posted by sergysergy Quote
Hi all,

Now that I have had my Kx (and 1st DSLR) for a while I feel like trying new things.

I have seen people talking about reversed lenses to get macro shots. I have a 18-55mm and a 55-300mm (kit lenses) plus a M 50mm f1.7 . Is there any cheap combination of lenses + adapters / extension tubes that may serve for this purpose at all?
I am not looking for anything fancy, just an alternative to expensive macro lenses to experiment with...

Thanks beforehand,
S
buy cheap $10 extension tubes and a 49mm to k mount adapter and your good to go. AND/OR buy a stacking adapter.... so 49mm to 52mm or whatever the filter threads are on those lenses.
03-08-2011, 09:58 AM   #15
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Aperture ring...

QuoteOriginally posted by sergysergy Quote
Hi all,

Now that I have had my Kx (and 1st DSLR) for a while I feel like trying new things.

I have seen people talking about reversed lenses to get macro shots. I have a 18-55mm and a 55-300mm (kit lenses) plus a M 50mm f1.7 . Is there any cheap combination of lenses + adapters / extension tubes that may serve for this purpose at all?
I am not looking for anything fancy, just an alternative to expensive macro lenses to experiment with...

Thanks beforehand,
S
as already mentioned, but I'd like to put a plug in for the wide angle lenses...they give you INCREDIBLE levels of magnification...my FA*24 f=2 is magnificent, but the working distance is SO close, and the depth of field is in the tenths of millimeters...but if you need a closeup of the left eyeball on the person appearing on a dime, this is the setup.

Lots of fun...watch out for that vulnerable rear element, though!

Cheers,
Cameron
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