A new 'portrait' lens arrived today. Cost me a whole ten bucks, one buck more than its near-twin. The spec? 135/2.8. The brand? Sears. That near-twin is a Focal, sold at K-Mart back in the day. These are both KR mount (the Ricoh pin is more like a ball bearing, quite harmless) and A-type, multicoated, solid, probably made by Tokina. The Sears weighs a little more than the Focal (400g vs 330g) because it has a "Macro Zone" ring that pushes the front element out a bit, knocking the close-focus from 1.5m to 0.75m. The Focal is good at 2.8 and sharp from f/4 up. The new Sears performs similarly. This is my first Sears prime; I have a few f/4 Sears zooms in the 70-210 neighborhood, in KR-A and M42 and Nikon mounts, each for US$9, that also perform quite well.
This Sears brings my tally of 135's up to 12. Of those, a Porst is fogged, and a Hanimex has sub-par IQ. The rest are good-to-very-good, from a Tak-B 135/2.5 (US$72, good with a hood) to the brilliant Jupiter-11 135/4 (US$38, slower but razor sharp). There's a saying that "It's hard to find a bad 135" and I believe it. And Sears-badged glass is seriously under-rated. But don't buy any 35s or 50s till I complete my collection, please.
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Now that everyone else has made recommendations, I'll chime in. Any non-cruddy 135 makes a good long portrait lens. I prefer my Tak-B f/2.5, or the Focal-A if I'm in more of a hurry. A bit shorter, I like my Meyer Trioplan 100/2.8 (US$27, M42). My Vivitar 90/2.8 macro (US$3, M42) is brilliant but a bit heavy, as is the Jupiter-9 85/2 (US$70, M39). My slightly-modded lightweight Nikkor 85/2 (US$9) is a constant companion now; protruding 50mm from the body, it provides a little something to hang onto. And I also use enlarger lenses in the 90-105-140mm range, on bellows, but you probably don't want to hear about those.
Generally, 70-150mm is long-portrait territory, especially 85-135mm. Decent stuff can be had in the 85-105mm range, including brilliant macros, and if you avoid new AF glass they needn't cost too much. But good 135mm glass is still dirt cheap.
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A couple things about stop-down manual metering, The Green Button. For any non-AF shooting, it's good but not necessarily required. For M-type lenses that aren't wide open, yeah, it's mandatory, but not for A-types, or anything with an A-M switch or presets. And if you're shooting portraits, where you control light and position, punching The Green Button a few times per session won't make you lose shots. No, M-types aren't really for action shots in variably-lit environments. I suppose you'd want something else for dimly-lit action portraits.