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11-10-2010, 12:36 PM   #1
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Reversing lenses

I want to get more involved in shooting macro, but don't want to shell out the money yet for a dedicated macro lens until I gain more experience. Other than trying my hand at using extension tubes, I also want to experiment with reversing my current lenses in order to see what kind of results are obtainable. I'm using a Pentax K-x with an 18-55mm lens as well as a 70-300mm telephoto.

Never having reversed lenses before, the obvious question is what kind of coupling mechanism do I need to purchase in order to attach the reversed lens to the camera body? What kind of item should I be looking for? Lens diameters are 52mm and 58 mm respectively.

Any assistance or advice is appreciated.

11-10-2010, 01:03 PM   #2
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Well, I looked into this earlier this year. I'd also suggest doing some searches on this site as there must be more info on this. I've found that reversing rings (what you need to do this) appear to come in two sizes for K mounts, 49 and 52mm. Not completely sure of this but that's what I found. You can get them from B&H or Adorama I believe. While I think you can do this with a zoom, I've not tried that yet. I've tended to use primes like a 50mm lens for this. All I can say is that 1) it works, 2) you and fully manual operation and exposure modes will become quite familiar, and 3) I think you will also need a lens which you can adjust the f-stop as your kit lens will be set at wide open.
11-10-2010, 01:49 PM   #3
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Just to add to the adapter issue - I have seen some that come with both 49 & 52 included.
11-10-2010, 02:22 PM   #4
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I'll have to look into it some more I guess. Reversing rings are the key words I was looking for, I couldn't remember what they were called. Thanks.

11-10-2010, 02:28 PM   #5
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I am wondering how functional reversing rings would be for a zoom lens, as opposed to a fixed lens. Anyone have thoughts on this?
11-10-2010, 02:36 PM   #6
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QuoteOriginally posted by Gary G Quote
I am wondering how functional reversing rings would be for a zoom lens, as opposed to a fixed lens. Anyone have thoughts on this?
Here's one from eBay that has both 49 & 52mm included. 49mm 52mm Macro Reverse Adapter Ring for Pentax K Mount - eBay (item 330379073113 end time Nov-15-10 02:05:16 PST)
11-10-2010, 03:35 PM   #7
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That ebay import allows any lens to become a "marco lens". I gotta get me one of them marco lenses sometime.

I played around and liked the close focus magnification I could get with reversing my 28-90mm lens. It takes a 58mm ring and you should be able to find them ranging from 49mm up to the 60's.
With my small zoom I get the best working distance from the subject together with greatest magnification if you will with the lens compressed to it's smallest profile. In other words I turn my zoom ring and focus ring until the lens is at it's shortest height. For some lenses that does not mean shortest focal length but the point at which the lens is the most compact.
I also have extension tubes for a 50mm that works well.
Of course with reverse mount rings, you have to meter exposure manually or use the stop down button, which works reasonably well. You still will need lots of ambient light or diffuse your flash some and close down your aperture.
With your longer 70-300 zoom reversed you may find it easier to work with a shorter lens when not using a tripod. Since you are moving the camera to find the focus instead of turning rings, you are going to be wanting less weight to try and hold steady for any length of time. Tripod use is best of course but not always handy.
11-10-2010, 03:39 PM   #8
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This is a good excuse to buy a cheap prime....

11-10-2010, 03:59 PM   #9
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Automation can be preserved by mounting a reversed lens onto a normally mounted lens, filter thread to filter thread. Adapters are available, though I have not bought one in a while.
11-10-2010, 04:10 PM   #10
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There are two lens reversing strategies for macro work.

1) Reverse mount the lens on the camera. This usually moves the lens further from the sensor resulting in a larger image. The lens' focal length must be shorter than 60mm or so for this to work well, if at all; the adapter is called a (Pentax K) Reversing Ring MACRO REVERSING RING 49mm FOR PENTAX K NEW IN BOX - eBay (item 160356122639 end time Dec-08-10 18:28:10 PST)

Reverse mounting a fixed focal length lens results in a macro lens that focuses over a small distance with essentially one magnification and you don't know what it will be 'til you try it.

It is practical to reverse mount the 18-55 zoom kit lens and get a range of magnifications. Here are example shots of a laptop screen (0.25mm repeat pattern):

Notice the piece of plastic tubing to control the aperture lever. Also notice the small working distance (clearance).

Reverse mounting your long zoom onto the camera most likely won't work. The lens will be too close to the camera.

2) You can also reverse mount one lens on another. This has the effect of changing the focal length of the combined lenses; the magnification resulting is original_focal_length/stacked_focal_length; for example a 50mm lens stacked onto a 100mm lens gives a magnification of about 2. The stacking is done with a filter ring with 2 sets of male threads called (52mm) Reversing Ring Male 52mm-52mm 52-52 mm Macro Reverse Ring / reversing - eBay (item 180420594619 end time Dec-10-10 08:40:26 PST) . You must be able to control the stacked lens' aperture by some scheme or other.

The working distance will be about the focal length of the stacked lens; in the above example, about 2".

Scheme 2) is fundamentally no different from stacking a close-up lens like a Raynox, etc on your primary lens. Often the smaller aperture of a reversed lens leads to vignetting - this is less of a problem with close-up lenses like the Raynox because they are pretty large. Following are the upper left quarter of macro photos showing vignetting for the stacked lens case:


Hope this helps,
Dave

PS The most effective thing for you to do I think is to buy a $55 Raynox DCR 150 (208mm) & put it on your 70-300mm lens. You'll preserve the features of your lens (even P-TTL automatic flash if it works with your lens now) and get magnifications from small to about 2X with a working distance of about 8". RAYNOX DCR-150 MACRO CLOSE-UP LENS 52mm 55mm 58mm 67mm - eBay (item 360303820136 end time Nov-22-10 23:06:46 PST)

Last edited by newarts; 11-10-2010 at 04:38 PM.
11-10-2010, 04:11 PM   #11
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When I reverse lenses I don't attach directly to the body, I attach in front of the longest and fastest telephoto I can. Then I reverse a short fast prime like a 50 1.7 or a 28 2.8 in front of it. You can get reversing filter adapters at B&H, Adorama or Ebay. You could use the two lenses you have and reverse the 18-55 in front of the 70-300 and set them at 18mm and 300mm respectively or even 55 and 300 if you wish. Divide the big number by the small number to get the magnification. Of coarse it's better to use a fast prime as the reversing lens but you can use what you have if you like. At 18mm you get 16:1 at 55mm you get 5.4:1. Or you can set your 70-300 to whatever focal length you wish to get the magnification ratio you are after. The beauty of this setup is you get to keep aperture and metering control over the lens that is attached normally to the camera. Call me spoiled but in my book that is a must. The down side is that's an awful lot of glass between the sensor and the subject. Expect a good deal of light loss and some CA to boot. Also keep in mind, the higher the magnification, the lower the DOF. At 16:1 you won't be able to get anything except a dust mite in focus. At 5:1 your DOF will be less then a mm and extremely hard to get just right.
11-10-2010, 05:05 PM   #12
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QuoteOriginally posted by Damian Quote
At 16:1 you won't be able to get anything except a dust mite in focus.
https://www.pentaxforums.com/forums/pentax-dslr-discussion/121734-dust-mites-...ml#post1259666
11-10-2010, 05:25 PM   #13
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if money was no object (canon mpe-65 not withstanding), what's the best way to get high magnification with decent light getting into the viewfinder and retaining full or at least partial control over aperture

and giving a decent (i.e. more than 1") working distance with suitable depth of field at f16...



I have the tamron 90mm macro, used a reversed 28mm on it, but mag was only about 3.5:1 and the working distance was about an inch, viewfinder was very bright still. So what combination of extension tube, teleconverters and reversed lenses will give the most magnification with decent optical quality?
11-10-2010, 05:45 PM   #14
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Just remember a reversed lens in front of the prime gives you a maximum working distance of the focal length of the reversed lens so a reversed 50 mm gives you a 50mm working distance or closer

While cheap and yielding good magnification lighting can be an issue
11-10-2010, 05:55 PM   #15
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Your link isn't working. Can you try and re-post please.
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