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
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.
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).