Originally posted by sergysergy Why are 90 and 100 2.8 lenses in general preferred over (more expensive than) 135 2.8 lenses?
Are they? For what, exactly?
135mm is a classic portraiture focal length from the 35mm film days. It has been well developed, much like other "standard focal lengths" like 35mm and 50mm, and f2.8 is rather slow for those purposes, at least by modern standards.
90mm and 100mm is a good macro focal length because it is not too long to be unwieldy, but it is still telephoto enough so you have some working distance. Macro lenses are very different design, highly corrected, and generally have smaller aperture. They are complex lenses, more corrections, has to focus all the way down to 1:1 magnification, and macro photos require DoF of f8-f16, often even more. Shooting macro at f2.8 gives incredibly shallow DoF, practically useless. Macro lenses used to be f4 and require a macro adapter on top of that to reach 1:1 magnification. Its an engineering marvel that these days a lens will go to 1:1 with fast f2.8 aperture.
Basically, you are comparing completely different lenses, with different features and different optics and different rendering. Something like FA 50mm f1.4 and DA 50mm f1.8 are much closer to each other than compared to DFA 50mm f2.8 macro. And there are enough differences between them to justify their existence. And the DA* 55mm f1.4 - designed for portraiture, as well!
Identify your needs, then get the lens that covers them well, at a decent price. Cost reflects many things, from construction quality to features, type of rendering, aperture, types of glass, rendering output. Cost alone is not enough to gauge how "amazing" a lens is
Edit: That said, I find the DFA 100mm WR macro to be very fairly priced. Its an amazing lens, stunningly sharp, very compact for what it is, looks stylish and it has good features like WR and QS. But for portraiture it is almost too sharp, too brutal, as it shows pretty much all flaws, skin blemishes on the person. And it has no "character" - it is just a clinical, lab-like rendering. For portraits you often want a lens that makes people's skin have a nice colour, doesn't expose all flaws, has pleasing, interesting bokeh. Portraiture is not just about capturing the person's nose and eyes, but about making a beautiful, painterly scene.