Canon Telephoto EF 135mm f/2.0L USM Autofocus Lens
One of Canon's Holy Trinity of lenses, the EF 135mm f2L USM is a staple in many portrait, fashion, indoor sports, and street photographers' bags. The 135mm f2L is able to shrink down the depth of field, thanks to its relatively large f2 maximum aperture. Since it's a longer telephoto lens, this allows the lens to compress the subject's surroundings, creating a very pleasing look that both highlights the subject and melts away distracting elements elsewhere in the frame.
Since this lens is a prime, you have the benefit of a large aperture that does not also require the lens to be uncomfortably large. Were there a telephoto zoom capale of 135mm and an f2 aperture, it would be completely unwieldy to hold and carry around, most likely weighing many pounds. But a 135mm prime is able to have a large f2 aperture yet still be no larger than a traditional walk-around lens. With the 135mm f2L USM, you get the advantage of 135mm reach and a shallow depth of field normally reserved for much wider lenses all the while being in a small enough package that it doesn't break your back to use. There's little wonder why so many professionals continue to use the 135mm f2L USM almost 20 years after it was released!
The Canon EF 135mm f2L USM is a relatively older lens, having been introduced way back in 1996, so it's probably on the short list to be refreshed by Canon. Nevertheless, it focuses very fast and accurately, a must for sports photographers who shoot in lowlight, and is extremely sharp across the frame, even by today's standards. If you're looking for a portrait or lowlight telephoto prime, the Canon EF 135mm f2L USM can't be beat for sharpness, aperture size, and focusing accuracy.