[axl]

I've seen few posts here and pics taken with lens reversed on to the camera. And last time I was in camera shop I saw inexpensive reversing rings for K mount. My question is: what purpose does it serve to reverse lens on the camera? Can anybody explain it to me please?
TIA Peter

[Buddha Jones]

I cant get too techy with my answer, but in short a reversing ring turns your lens into a macro, which is great, but the working distance to get things in focus is in the milimemters, which is not so great.

[alohadave]

There are two types of reversing rings.

1. male-to-male filter threaded reversing ring. This allows you to put two lenses face to face to create a 'macro' combination that allows very close focusing.

2. male filter thread to lens mount ring. This allows you to mount the reversed lens directly to the camera.

Some things to consider. When you are reversing a lens, unless you have an older manual lens, you will need to either hold open the diaphragm with your finger, or rig something up to hold open the diaphragm. Manual lenses default to having the diaphragm wide open so this isn't an issue with these lenses.

Your working distance is millimeters wide, at best. If you will be handholding, you'll need tons of light, and even then, camera shake will be an issue. SR isn't really usable since the camera has no way of know what lens you have mounted.

One way to focus is to set up the camera on a tripod and use the center column to move the camera up and down to get what you want into focus.

[RichardW]

Ditto to the above.
All camera operations have to be manual.
Have been using reverse rings since way back, when we only had 35mm.
The attached spider was only 1/8 of an inch across its whole body. But with a lot of experimentation, you can get some amazing images

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[Entropy]

The idea with a reversed lens mounted directly to the camera (or more frequently, using an extension tube too) is this:

Most lenses are designed to take a subject at a reasonably long distance from the lens and focus an image of it only an inch or two behind the lens. When doing the opposite, IQ suffers. An extension tube + reversing ring reverses this situation.

For a reversed lens mounted to another, I believe that for two lenses focused to infinity, the magnification (ratio of image size on sensor to subject size) is equal to:
FL(normal)/FL(reversed) - e.g. for a 50mm lens reversed on a 150mm lens which is mounted to the camera, the magnification will be 3:1 (sensor image is 3 times that of the actual subject) - This is pretty nice, as usually either dedicated macro lenses or extension tubes are needed to even hit 1:1.

[axl]

Ditto to the above.
All camera operations have to be manual.
Have been using reverse rings since way back, when we only had 35mm.
The attached spider was only 1/8 of an inch across its whole body. But with a lot of experimentation, you can get some amazing images

what if I reverse lens (manual with aperture fully open) on another lens. Can I AF/meter with the "normal" lens?

The idea with a reversed lens mounted directly to the camera (or more frequently, using an extension tube too) is this:

Most lenses are designed to take a subject at a reasonably long distance from the lens and focus an image of it only an inch or two behind the lens. When doing the opposite, IQ suffers. An extension tube + reversing ring reverses this situation.

For a reversed lens mounted to another, I believe that for two lenses focused to infinity, the magnification (ratio of image size on sensor to subject size) is equal to:
FL(normal)/FL(reversed) - e.g. for a 50mm lens reversed on a 150mm lens which is mounted to the camera, the magnification will be 3:1 (sensor image is 3 times that of the actual subject) - This is pretty nice, as usually either dedicated macro lenses or extension tubes are needed to even hit 1:1.

Thanx for this detailed explanation...

Just one more question, if I reverse lens directly on camera body, how do I meter?

[axl]

One more question:
If I reverse lens like Hoya 135 (old metal manual) or Sigma 105 on let's say DA40 won't the weight damge the fron element? I don't think it's designed to carry weight like that?...

[Entropy]

One more question:
If I reverse lens like Hoya 135 (old metal manual) or Sigma 105 on let's say DA40 won't the weight damge the fron element? I don't think it's designed to carry weight like that?...

I'm fairly certain that for high magnification, you don't want a configuration like this anyway. You want the shorter lens on the end.

For example, my setup once I get a reversing ring would be something like:

Takumar-K 135 on camera
Reversing ring on the 135
SMC-M 50/2 reversed on the ring

[axl]

I'm fairly certain that for high magnification, you don't want a configuration like this anyway. You want the shorter lens on the end.

For example, my setup once I get a reversing ring would be something like:

Takumar-K 135 on camera
Reversing ring on the 135
SMC-M 50/2 reversed on the ring

In that case I would reverse DA40 on to Sigma 105 BUT DA40 won't stay wide open while off the camera (unless I won't tape the pin). The only lenses I have with apperture ring, are Sigma 105, Tamrons 28-200, 70-300 and Hoya 135, so what now? hm, maybe LBA will sort it out

[Entropy]

In that case I would reverse DA40 on to Sigma 105 BUT DA40 won't stay wide open while off the camera (unless I won't tape the pin). The only lenses I have with apperture ring, are Sigma 105, Tamrons 28-200, 70-300 and Hoya 135, so what now? hm, maybe LBA will sort it out

50mm Ms are CHEAP.

[Canada_Rockies]

50mm Ms are CHEAP.

And 28's give about twice the magnification. A 28 reversed with a K ring gives about 2X on the film or sensor.