Tamron model 272E Macro for Canon
This guide is about the Tamron model 272E Macro lens for Canon EOS cameras, although some aspects may also be of interest to users of other lens mounts. The comments on functionality are based on one lens purchased directly from Asia via eBay.
First the CAUTION: The Tamron SP AF90mm F/2.8 Di Macro 1:1 for Canon Model 272E is a new revision of an earlier 90mm Tamron macro lens. The older lens should be considerably cheaper, so make sure you know which one you are bidding on. The features of this new model are redesigned for improved functionality for digital cameras.
DESCRIPTION The lens is a little over 10 cm long when focused to infinity. It is about 15cm (~6") long when focused to its closest distance of 0.29m (0.96 ft) for 1:1 reproduction. In the case of the Tamron 90mm, the deeply inset front lens element means that the actual distance from the front of the lens barrel, however, is only about 10cm (~4") from the subject. There is room for lighting of the subject being photographed--an advantage over shorter focal length macros that may leave only a tiny space between the front of the lens and the subject--but clearly if distance from the subject is critical, a longer macro lens such as 180mm focal length may be a better choice. The Canon version of this lens has no aperture ring markings on the lens, unlike the Nikon and Pentax versions. Aperture is displayed in the viewfinder and on top of the camera, of course. The lens comes with a hood and a pouch.

FOCUSING The autofocus is not so quiet as the fancier Canon lenses, but is fairly fast. There is an extremely useful knob for limiting the focus range to speed up focusing in either macro or normal mode. In general, autofocusing for normal use seems equivalent to that of Canon lenses. In the macro range, the lens may go back and forth before finding a sharp focus point, but depth of field at macro settings is so small that manual focusing is likely to work better in any case.
The lens is either in autofocus or manual mode. When autofocus is engaged by pulling out on the lens barrel until a solid click is felt, the manual focus ring is disengaged, so there is no danger of manually damaging the autofocus mechanism on the Canon version of the lens. When the focus ring is pulled back, the lens snaps into manual mode, which has an excellent feel and control. The front of the lens does not rotate in focusing so polarizers or graduated filters can easily be used. And, by the bye, although the Di indicates that it has been redesigned for digital cameras, it is can be used on 35mm cameras as well as on full-frame or aps-sized sensor digital cameras.

LENS QUALITY Macro photographs taken with the lens are sharp to the edges and show no visible pincushion or barrel distortions. This lo-res macro picture is only an illustration of the linearity of the lens, not its sharpness.
The lens is very sharp, and has done well in tests and reviews. It is also relatively fast for digital lenses.

BOTTOM LINE Is this lens a good buy? As an on-line search will reveal, there have been a number of reviews of this lens by major photo magazines, and my reading of them is that this is a lens that is among the top contenders for macro lens quality, regardless of manufacturer. Careful eBaying will reveal occasional real bargains for this lens, but even at its regular mail order discount price, it can be highly recommended. I know I am very pleased with the one I have.