Maybe you've been playing around with macro photography, either with a dedicated 1:2 or 1:1 prime macro, or with a zoom lens that close focuses to about 1:3 magnification. Maybe you've even experimented with extension tubes or magnification filters to get even more macro action through your viewfinder.
But if you want to get even more extreme closeups, there's one lens that's probably the ultimate macro lens: the Canon MP-E 65mm f/2.8 1-5x Macro ($829, street). Don't get confused by the name. This is a constant f/2.8 lens, but the magnification runs from 1:1 to 5:1. (1:1 will capture 1 millimeter as 1mm on the sensor. 5:1 will capture that 1mm as 5mm on the sensor plane -- we're talking extreme, here!)
Unlike your plain-vanilla macros that can double as workaday portrait and landscape glass, the Canon MP-E 65mm lens is a lens dedicated solely and wholly to macro photography. Unlike other macro lenses, you cannot focus this lens beyond the maximum distance of 4 inches. So while it is truly a one-trick pony, it's really one impressive specialized lens.
The main reason to use this lens is the MP-E 65mm's variable magnification ratio and extremely close working distances. A standard macro lens will have a working distance (the distance from the front element to subject) in the neighborhood of 6-8 inches and a life-size magnification ratio (1:1). The MP-E 65mm's variable magnification ratio ranges from life-size to five times life-size (5:1). The working distance of this lens decreases as you progress your way up the magnification ratio, starting at 4 inches at 1:1 and ending up at 1.6 inches at 5:1. To put it another way: The MP-E65mm will only be in focus at these focal lengths. You cannot have 5:1 magnification at a distance of 8 inches. If you want 5:1 magnification, your subject must be 1.6 inches from the lens.
The short working distances can be frustrating at first and the difficulty is amplified by that small front element. While the front of the lens barrel is 58mm in diameter, the front element is approximately 20mm in diameter (roughly nickel-sized). You truly have to have your subject centered in the front of the lens and it is easy to misdirect the lens towards your subject. After having many of my subjects fly, crawl or hop away before I could get them framed in the viewfinder, I found it easier to locate the subject at the 1:1 setting and zoom to the desired magnification.
Other ways to go beyond Life-sized
• Extension tubes can boost magnification by increasing the distance between the lens and the sensor plane. These are available for all brands of cameras and lenses.
Technically, this is a manual focus lens, insofar as there's no motor drive to be found, but that term is a little deceiving. Standard manual focus lenses have a focus ring that you turn to adjust your focus. This is not the case with the MP-E 65mm. The adjustment ring on the MP-E 65mm is used to set your magnification and you move your camera to adjust or fine-tune the focus. In a roundabout way, you can fine tune the focus by turning the lens ring but in doing so, you affect the magnification ratio. In some cases this won't make any difference in the appearance (can you tell the difference between 4:1 and 3.75:1 magnification at a quick glance?) but I found it easier to fine tune the focus by moving the camera. If you are serious about this lens, you should consider a set of rails for ultra-fine distance adjustments.
This lens can be used unsupported but when you venture beyond 3:1 magnification, the camera movement is dramatically amplified and a sturdy tripod is highly recommended. Because of the short distances and higher magnifications, depth of field is ridiculously shallow and extremely sensitive to the slightest movement. For example, at 5:1 magnification, Depth of Field is approximately .05mm and it only takes moving the lens a literal hair to shift your depth of field, knocking the subject out of focus!
The MP-E 65mm is compatible with most ring flashes. However, when shooting above the 4:1 settings, I found the ring flash over-shoots the subject. For the higher magnifications, a macro twin flash system such as Canon's MT-14ex is probably a better idea, so you can turn the flash heads more inward towards the front of the lens to better light your subject. The ring flash also makes the closer focusing distances difficult to achieve simply because the flash extends the length of the lens about one inch. You may also want to check out the macro spotlight technique shown here.