What "Reverse Ring" specs (size..etc) for my Canon 600d for Macro Photography?

Question

I have these three lenses, and I wonder which one of them is the best to be used with "reverse ring" for Macro Photography?

Camera: Canon EoS 600d

Lenses: 18-55mm, 50mm, 50-250mm

Answer 1

If you want the highest magnification possible, then the 18-55 might yield that at 18mm. But if you want better image quality, the 50mm f/1.8, being a prime will probably yield that.

BTW, there are two types of macro reversal rings: ones that let you mount a reversed lens directly to the camera mount, and others that are basically male-to-male filter rings, which let you mount one lens reversed on the face of another lens mounted on the camera.

See also: http://digital-photography-school.com/reverse-lens-macro-close-up-photography-lesson-3/

Answer 2

One might wish to inquire “what’s the advantage of reversing a lens”. The normal design of a camera lens is to image a curved vista and project this image on a flat surface such as film or digital chip. When we image super close, in most cases the subject will be flat or nearly flat and depth-of-field will be super shallow. Best we use a lens that is optimized to image flat surfaces. By reversing the lens we are using the back-focus to image and the front-focus to project on the sensor. The back focus is optimized for a flat subject. Additionally, the reversing ring adds space; the lens barrel is placed further away from the chip’s surface. This added distance yields a little more magnification. A macro lens is optimized to image at “unity”. This is life-size (1:1).