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| p.1 #12 · Fast Glass Technology/Related Question? |
A lot of slow lenses are excellent performers from wide open, something often overlooked but which makes the lens more consistent over its aperture range - a great advantage.
The universal kit lens being say f3.5-f5.6 gave the market the idea that slow=bad and fast=good which morphed into slower=worse and vice versa.
It boils down to fast lenses being suitable for subject matter, portraits mostly, where either bokeh considerations, focus fade and image centres dominate and the outer frames matters little - the modern look, if you will; and slower lenses being more suitable for general photography where you want all-of-frame excellence, low distortion, flatness of field and lower (other) residual aberrations at middle apertures. Also such near perfection is considered old fashioned.
Looking at Leica's great R 80-100mm lenses, at f5.6 the 80/1.4 in no ways rivals the sheer performance of the 90/2AA or the 100/2.8 APO. In fact, the latter two are much better at f2.8 than the poor old Summilux, and the 90/2AA is better at f2 than the Summilux at f2.8.
The message is that even for very high end lenses, you generally cannot deliver the same performance at middle apertures compared with mundane f2/f2.8 lenses. Few images *require* such fast apertures. The kinds of photography are very different, of course, and many people need both kinds. But - just saying, f2-f2.8 seems a much better sweet spot overall, despite the fast lens slavering we see so much of.