Another one of those frequently asked questions that I get is about Canons MPE-65mm macro lens. There doesnt seem to be very much information on the web about it even Canons own web site gives very little details. So if youre curious about one of the best pieces of macro equipment on the planet then keep reading
The MPE-65 doesnt really have a focus ring -it is always focused at the maximum magnification that you have it set to and there is no infinity focus. No auto focus either not that it would really do you any good anyway. The depth of field is so thin when shooting at life size and higher magnification that you wouldnt want the camera to decide whats in focus and whats not. One of the reasons why I tell people to stop centering their images, other than the obvious compositional mistake, is that the focus indicators in the view finder don't work when the MPE-65mm macro lens is attached to any Canon camera body. So you have to be good at focusing the scene with nothing to aid you other than the image you see in the view finder. I try to key off of textures like hair, scales, etc. If you are using a standard macro lens now then get use to focusing it without using the focus indicators in the view finder -it will make moving to the MPE-65 a lot easier.
There is a ring on the lens that controls a variable length extension tube, and as you turn it you can go from life size to five times life size and every magnification in between. So you will only be shooting macro with it -not possible to get a shot with a lower magnification than life size. If you look closely at the design of the MPE-65 it's really a reversed lens with a variable length extension tube built into it.
The advantages: No need to add or subtract anything from the lens to change the magnification all you have to do is turn a ring. If you've ever juggled a lens and tubes out in the field you'll understand how easy it is for the MPE-65mm to spoil you!
Image quality is on par with "L" glass -I do very little editing, less than two minutes for any single image, and I can get the colors to "pop". The lens is also razor sharp so sharp that a lot of people have wondered if the MPE-65 is better at controlling diffraction than other lenses. But as good as the lens is it cant undo the laws of physics. What some people are calling diffraction in other macro lenses is really due to the lens not producing a sharp image circle or what I call macro motion blur movement during the duration of the flash that is only the equivalent of one or two pixels in length on the sensor. Not enough to be easily detected as motion blur, but enough to cause the image to look a little soft. The MPE-65 is so sharp that you can use it at F16 up to twice life size, and up to F11 all the way to five times life size and still get sharp images (depending on the size of the subject). I often shoot above 3x at F14 because opening up the lens 1/3 of a stop to F16 makes a noticeable difference in image quality. IMHO the MPE-65 has difficulty producing a sharp image circle at F16 above twice life size, but I dont think the problem is related entirely to diffraction (opening up the lens 1/3 of a stop shouldnt make a difference in diffraction softening).
You can attach the MPE-65mm directly to Canon's 1.4x and 2x teleconverters for a maximum magnification of 7x and 10x respectively. But the lens won't communicate accurate aperture information to the camera, so keep in mind that you're actually shooting one Fstop higher than what the camera is displaying with the 1.4xTC and two Fstops higher with the 2xTC.
The downside to every macro lens is the working distance. I wish the MPE had more, but I could say that about every macro lens. It's not about getting close to the critters -I can do that no matter what I'm shooting with. But it's nice to have a lot of room to maneuver when I'm trying to compose a shot and bumping into the plant the critter is on is almost always a buzz kill
On the plus side the short working distance allows me to grab onto the flower an insect is feeding from with my left hand and then rest the lens on that same hand to help keep everything steady. The image included with this deviation was made possible by the MPE-65mm's two inch (5cm) working distance at three times life size.