[Michael Piziak]

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I've been using the Asahi Pentax extension tubes (3) and the Asahi Pentax macro f4 100mm lens for macro photography to get close.

This guy, however, a Pentax user, seems to really get closer in with his extension tubes and a reverse 28mm prime lens:

You Tube

You Tube

Which 28mm lens is recommended or is he using? I may pick one up and an adapter to try to get closer in. (is it this lens: SMC Pentax M 1 2 8 28mm Prime Wide Angle Lens in Fantastic Shape | eBay)

[OregonJim]

The only type of lens I would stay away from in this application is one with aspherical elements. They are designed to bend and converge light in the "normal" direction of travel through the lens, and may cause convergence issues when reversed since the glass is not symmetrical.

[calculator01]

I have used my A28 and M50 with extension tubes and a reversing ring for macro. I personally do not like the 28 because of the working distance.


but, the nice thing is the 28's I have seen are all 49mm threads. Therefore one reversing ring works for all those old 50's, the Limiteds, and I have seen some 200mm lenses with 49mm threads. Almost bought a Minolta lens for this purpose.

[baro-nite]

The "K series" 28/3.5 is exceptionally good reversed. The much cheaper and easier to find M28/2.8 is also quite decent reversed, although you have to stop it down a bit more than the K28/3.5 and hence it is not as good at higher magnifications (3:1 and beyond). Various 50mm lenses are also good reversed. The M50/1.7 does quite well, but 50mm macro lenses do better. Enlarging lenses can also be good, and some are quite cheap.

Much depends on what magnification you're after.

[bluestringer]

I have reversed my 50 onto my 100, both f4 macros, and I just can't get the right lighting to get a decent image. I want to try reversing my 50's onto some tubes, but still working on some different lighting right now.

[marcusBMG]

Since Michael has started a reverse lens thread, I'm sure he will allow me to add to it with this qq.

I have picked up a nice Kiron Reverse Mate. It's a vastly superior item to the basic lens reversing rings from china available on evilbay. It's about 15mm thick so adds that extension to the lens. Now my qq is: with a reversed lens does that extra extension over the couple of mm of the chinese ones increase or decrease the magnification ratio (my sense of it is decrease)? And by how much?

Once I get my 55mm to 49mm step up ring then I'll be checking it out with my smc-m 50mm and my helios.

[baro-nite]

with a reversed lens does that extra extension over the couple of mm of the chinese ones increase or decrease the magnification ratio (my sense of it is decrease)? And by how much?

Just as with a lens mounted normally, more extension gets you more magnification, by a factor of extension/focal length. E.g., a 28mm lens reversed with minimal extension will give something roughly around 1:2 magnification (IIRC); adding 15mm extension will make this around 1:1.

I just can't get the right lighting to get a decent image

As magnification goes up, effective f-number goes up too. A 50mm reversed onto a 100 gives you 2:1, so the effective f-number will be 3 times the setting on the 50mm (you should leave the 100 wide open). So you need more light than you might expect.

[marcusBMG]

Thanks for that clarification baro-nite.