[davea]

I have a K110D and I want to get a reversing ring. I have a Sigma DG 70-300 and a Pentax 28-80 lens. The reversing rings comes in different sizes. What size should I by for each lens? Thanks

[i_trax]

the reverse ring attaches to the front of the lens so it has to be the same as filter diameter

[Apet-Sure]

People use reversing rings to take macro shots; not sure they have another purpose. Someone can correct me if I'm wrong. The thing is, in order to take really close macros you need to use wide angle lenses. Remember, you are reversing the magnification of the lens. A telephoto lens reverse mounted will push the subject away. Your 28-80mm set at 28mm or so may do well. But as you zoom 'in' you'll be zooming 'out'. It just depends on what you are trying to accomplish. Of course, you can make the argument that no photography experiment is wrong.

Welcome to the forum; nice to have you.

[UncleVanya]

You can get any size and then use step rings to fit to the lenses. I suggest getting one that is close in size if possible. In personally only have 52 and 49mm versions. I also do not use them on lenses outside this range since I have plenty of Macro options.

[pacerr]

I've DIY-ed a number of field expedient reverse-rings and extension tubes using salvaged lens bayonet rings or body caps and 'empty' filter rings and lens caps epoxied together.

These were made for a Q-macro lens project and included an extension ring spacer made from a flashlight but should offer an idea or two.


[An A110 70mm lens using a cannibalized bellows for a focusing rail for anyone curious.]

[PWhite214]

Just use the 'search phrase' :XY mm reverse ring Pentax K on EBAY. A 58 mm costs about $4 US.
Phil

[davea]

the reverse ring attaches to the front of the lens so it has to be the same as filter diameter

Just to clarify, I have a 58mm UV filter on the lens now. So, I should get a 58 mm reversal ring?

Thanks,

[boriscleto]

CHEAP MACRO -- Buying or exploiting a lens for ultraclose work - PentaxForums.com

LENS REVERSAL: Many macro shooters work with a reversed prime lens -- but reversal just brings you close to your subject. (Working distance is about 45mm with Pentax-type prime lenses.) You still need some extension to gain magnification. A lens with a deep front inset effectively has built-in extension; others may need an added tube. Lens-reversal is cheap, easy, and clean. Just about ANY lens can be reversed. That's how I recycle some non-Pentax lenses that I would otherwise not use. Or I can use a Pentax lens normally, for non-macro work, then flip it around to get real close.

You can reverse a zoom. DA lenses lack aperture rings; they won't do. But any FA or F or MF zoom can be reversed, with a working distance somewhere around 1.3-2x the focal length. Even a lousy zoom, reversed, can give good results. I do this with the A35-80, arguably the worst lens Pentax ever sold. At 35mm I get 1:1 magnification at about 5cm distance; at 80mm I get 1:2 magnification at about 15cm, and it will focus past infinity. A real macro-zoom! Not quite as good as my Schneider Betavaron 50-125/4-5.6 enlarger zoom, but that's another story...

PRO: Cheap and easy; flatfield sharpness.
CON: Close working distance; no auto control.

REVERSE-STACKING: You can reverse-stack lenses and can gain great magnification. Mount a longer PRIMARY lens on the camera; then use a male-male thread-reversal ring, then screw a shorter SECONDARY prime on that. (If you're really cheap, just use gaffer's tape to hold the lenses nose-to-nose.) Magnification is the ratio of the Primary:Secondary focal lengths. A 35mm secondary stacked onto a 105mm primary gives 105:35= 3:1 magnification. A 25mm stacked onto a 200mm gives 8:1, which gets into MICRO-photography territory.

The Primary can be a zoom, although I prefer primes. The Secondary should be a manual prime with an aperture ring. Use the Secondary's aperture ring to control exposure, and leave the Primary wide open. Stopping-down the primary can cause vignetting. You want the front objectives to be fairly close together; lenses with deep insets can cause vignetting. Changing distance between the lenses will change magnification very very slightly. Try it and see.

Reversing or stacking primes ALWAYS puts you at that same close working distance of about 45mm. That is good for studio work; not so good for the field. Be sure to use a hood with any reversed lens, to reduce flare. HINT: Macro tube sections work well as hoods.

PRO: Easy to achieve great magnification; flatfield sharpness.
CON: Close working distance; no auto control; eats light.

CHEAP EXTENSION: I love simple cheap extension (tubes and/or bellows). You can put a prime or a zoom on extension for close and macro work; I prefer primes. An Industar-50/3.5 on 50mm of cheap M42 tubes with a safe cheap wide-flanged M42-PK adapter puts you at 1:1 for a pittance. For not much more, is my favorite: cheap bellows and tubes mounting cheap enlarger lenses, copy lenses, other lenses without focusing mechanisms of their own -- non-camera lenses. You can shove just about any optical material into a bellows!

Many many types of tubes and bellows exist; I can't discuss them all here. I prefer cheap simple ones, and not only for macro work. Both PK and M42 tube sections can be used as adapters for weird lenses -- just glue a tube section to the lens body. Tube sets are dirt cheap, often well under US$10 shipped for 50mm of extension in 3 modular sections. I have about 6 sets of each and I need more. M42 bellows are cheap, PK bellows are a bit more. Bellows for other mounts can often be easily adapted to PK -- just replace the mount hardware with a cheap flanged M42-PK adapter.

NOTE: A-type is NOT the same as so-called Auto macro tubes. Whether M42 screwmount or PK bayonet mount, these have a mechanical linkage to close the lens iris, not the electric contacts that allow camera-lens communication and control. PK 'Auto' tubes can be used in M(anual) shooting mode and will stop-down the iris with Green button use. M42 tubes will not work this way on our dSLRs.

PRO: Cheap; clean; flexible usage.
CON: No auto control; eats light.

[pacerr]

. . . I should get a 58 mm reversal ring?

Look at it this way; you're using a filter that has a male lens bayonet ring (or M42mm threads) instead of filter-glass on the front of it so you can mount the lens 'backwards'.

[i_trax]

Just to clarify, I have a 58mm UV filter on the lens now. So, I should get a 58 mm reversal ring?

Thanks,

yes , that's correct

[davea]

yes , that's correct

Thanks for the clarification