Tamron SP 90mm f/2.5 Macro (52BB) Adaptall-2

Macro glass in 1979 was understood as documentary kit: flat-field copy lenses optimized for shooting coins and insects dead-on, clinical by design. Tamron's first 90mm f/2.5 broke that rule on purpose. They computed it to render beautifully at portrait distance and at infinity, not just at 1:2, and built it as a founding lens of the SP (Super Performance) line. That single decision is the entire reason people still hunt these down. The 52BB is the late revision of that original 52B. Optically the two are identical; the visible changes are cosmetic, the most useful being the move to a 55mm filter thread from the earlier 49mm.

The whole thing hangs off Tamron's Adaptall-2 system, which is the clever part of the history. Instead of building a Nikon version and a Canon version and an Olympus version, Tamron made one lens and sold a small bayonet adapter for every mount going. Buy the right Adaptall foot and this 90mm bolts onto an F-mount Nikon, an OM Olympus, a screw-mount Pentax, whatever you own. That universality is why these turn up cheap and everywhere four decades later.

Eight elements in six groups, and the reputation is bokeh first. Wide open at f/2.5 the background dissolves into the smooth, rounded falloff this lens is loved for, the rendering that made people simply call it the Portrait Macro (Japanese shooters know it as the Tamukyu). Center sharpness is already strong at f/2.5 and snaps to genuinely excellent by f/4 to f/5.6. Contrast is moderate rather than punchy, which on color negative film reads as a gentle, flattering tonality on skin. The multicoating keeps flare honest, though shoot it straight into a hard light source and contrast will still wash a little.

The real limitation is the macro range. This is a 1:2 lens, half life size, focusing to about 0.39m on its own. Want true 1:1 frame-filling bug shots and you need the matched extension tube, or you step up to Tamron's later 1:1 72B. For portraits and head-and-shoulders work that ceiling never matters, but go in expecting a half-macro that doubles as an excellent short tele, not a full reproduction-ratio macro.

Today it sits in the bargain-cult tier. People cross-shop it against the Vivitar Series 1 90mm and the various 100mm f/2.8 macros, and the Tamron usually wins on rendering for the money. It stays popular with film portrait shooters and mirrorless adapters who want a 90mm that draws with personality rather than flat neutrality.

One metering note for close work. As you rack this toward 1:2 the effective aperture drops because the lens is physically extending, so a meter reading taken off the subject will under-expose unless you add compensation. At half life size that is roughly a stop. Zone Light Meter computes the bellows factor from your focal length and extension, so dial in the magnification and let it fold the correction into the reading instead of guessing in the field.