What are the biggest differences between Reversal Rings, Extension Tubes and Macro Lenses?

As far as I understand all three options help you do macro photography but are their other reasons for having the three different items? I figured reversal rings and extension tubes were just for the low cost but with additional more expensive features being added to the two options it seems there may be certain situations for each type? What are their biggest differences and advantages over each other?

• Are there situations where you would have one over the other?


• Do all three options have the same "wafer thin" depth of field?


• Do they all suffer from the same light loss?


• Do any of them affect your photos more negatively than the others?


• Can I achieve the same magnification with rings and tubes that I can with proper lenses?


• Would you ever combine these options together or would there be no need for that?

I ask because I recently bought a cheap extension tube and reversal ring and I'm trying to get a better overall understanding of each. I tend to use the extension tube a lot more, because I can put it on my 70-200 and have a workable distance between subject and lens.

This photo was taken with 49mm of extension tube on the 70-200 I believe which may be greater than 1:1. Would it be sharper with a macro lens?

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Answer

Depth of Field

Reversing a lens will produce a very shallow DOF. You may also get distortion and vignetting and have difficulty focusing, as you can only focus at a very narrow range of distances. From memory extension tubes have less DOF than a macro lens, but I am not certain of that.

Light Loss

You will lose 1-2 stops of light using extension tubes. You can argue that macro lenses at 1:1 lose some light (mine reduces from f/2.8 to f/3.5). I don't know about the loss of light with reversed lenses, but it would would seem clear that the light gathering ability of the lens would be reduced when reversed, given that the aperture opening tends to be quite a bit smaller than the front of the lens.

Magnification

You can achieve 1:1 with extension tubes with say roughly 50mm of tubes and a 50mm prime lens. Reversing a lens you can get greater than 1:1.

Quality and Ease of Use

You will lose sharpness in reversing a lens or using extension tubes. You may lose metering and AF capability with a reversed lens (and some tubes), although some reversing rings and extension tubes have metering capability.

An important difference to me is that macro lenses can focus from their min distance to infinity (other two options have a narrow range of focus ability, so the camera and subject must be a certain distance apart). So once you reverse your lens or put on some extension tubes, you will be locking in a certain magnification and subject-camera distance, where a macro lens you can move closer or further away from your subject to compose the shot.

Reversing a lens, or sticking it at the end of some extension tubes, you are not using the lens for what it was originally designed and optimised for, so you wont get the same performance as a dedicated macro lens.

But both options do a good job considering the relatively low cost.

Re: your new question about using them together. Yes, you can use an extension tube or teleconverter with a macro lens to increase magnification, or to give you more working distance for the same magnification. With more working distance and the same magnification, because you are focusing at a greater distance, you should end up with more DOF as well.