Used Leica Tri-Elmar-M 28-35-50mm Price Guide

The E55 (1998–2002) and E49 (2002–2007) refer to the filter thread diameter: 55mm and 49mm respectively. The E55 was the original Tri-Elmar as launched; the E49 is a redesigned smaller, lighter barrel with the same optical formula. They are optically identical: both produce the same image across all three focal lengths. The E49 is more compact and better-balanced on small M bodies (M6, M7); the E55 is bulkier but functionally equivalent. Most working users prefer the E49 for handling reasons; collectors slightly prefer the E55 for being the original.

Yes, on every digital M from the M8 onward. Late-production E49 examples (roughly post-2006) include factory 6-bit coding on the rear flange, which the digital body reads to apply lens-specific corrections and write the focal length into EXIF based on the click position. Pre-2006 examples are uncoded: the lens still mounts and shoots, but you'll need to set the lens manually in the body's lens menu or have it 6-bit-coded by a Leica service center for about $200.

Neither, strictly. The focal-length ring clicks into three discrete positions: there are no intermediate focal lengths and the ring physically resists movement between stops. Internally, the lens repositions its optical groups when the ring clicks; each click is essentially a separately optimized configuration. Think of it as one body that contains three lenses, accessed by a click ring rather than by changing barrels. M body frame lines change automatically when you click to a different focal length, just as if you'd mounted a different prime.