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Most of the reviews of the Pentax fifties contain words to the effect that they aren't super sharp around the edges of the frame wide open, but that they sharpe

Most of the reviews of the Pentax fifties contain words to the effect that they aren't super sharp around the edges of the frame wide open, but that they sharpen up by f/2. I don't have any background in optics, but I've operated under the assumption that most lenses at full aperture necessarily compromise some resolution for speed, meaning you have the same loss of resolution with a 28mm or 35mm lens at full aperture. Are other focal lengths of different designs where this doesn't hold true? Do modern sensors have enough more resolution than film that they show the loss of sharpness in the lens at smaller apertures? I'm curious because I'll be looking for a (used) DSLR body at some point in the next few years. At least in the Pentax world, most of the commentary about old lenses on new bodies centers around the lack of the mechanical aperture coupling on the newer bodies, and the compromises stemming from that (stop-down metering, mostly).

rangibaby 8y ago
> Do modern sensors have enough more resolution than film that they show the loss of sharpness in the lens at smaller apertures? Film quite obviously shows soft corners too, just most people didn't care because they weren't obvious at the sizes normal people view or printed photos. I wouldn't worry about soft corners to be honest. It's like criticizing a classic muscle car because it has a slower 0-100 than newer ones
- jasomill 8y ago
  I agree. And if your underlying question is "are these lenses going to take good pictures with this camera", the best advice I can give is: try it! I say this because some of my favorite lens/camera combinations are those with issues far beyond mere unsharpness, and that would likely be rejected by the mass of Internet forum cognoscenti in favor of native lenses that I know from experience that I'd never use even if I already owned them. Case in point: an old Arri/Zeiss 16mm f/1.2 cine lens that I shoot on Micro Four Thirds, despite the fact that it was designed for the much smaller 16mm (motion picture) format: in spite of edges are soft at all apertures, corners that aren't so much "soft" as "missing altogether", an overall image almost certainly less sharp than the average native kit zoom, and various other technical considerations compromising optical performance, I enjoy both the process of shooting with the lens and the results when I do. So why, then, should I give a damn what the Internet thinks? Whereas, I sold the more "appropriate" Panasonic 15mm f/1.7 native lens several years ago, at a considerable loss, for lack of use.
Sharlin 8y ago
For instance the archetypal modern nifty fifty, the Canon 50mm f/1.8 (any version) is tack sharp at f/2.8, and exceedingly so at f/4, but the larger apertures are... less than optimal. Including the center of the frame. There's readily visible halation (caused by ill-corrected spherical aberration?) that gives everything a soft, dreamy look, plus severe purple fringing around contrasty features (chromatic aberration). There are many recent lens designs that are tack sharp all over the frame already at maximum aperture, outresolving even a modern high-pixel-density APS-C sensor. But those have complex optical formulas and consequently are almost always large, heavy, and expensive. For instance, the extremely sharp Sigma 50mm f/1.4 A weighs 815 grams compared to the 290 grams of the venerable Canon 50mm/1.4, and the 130 grams of the plastic fantastic 50mm/1.8!

rangibaby 8y ago

> Do modern sensors have enough more resolution than film that they show the loss of sharpness in the lens at smaller apertures? Film quite obviously shows soft corners too, just most people didn't care because they weren't obvious at the sizes normal people view or printed photos. I wouldn't worry about soft corners to be honest. It's like criticizing a classic muscle car because it has a slower 0-100 than newer ones

jasomill 8y ago
I agree. And if your underlying question is "are these lenses going to take good pictures with this camera", the best advice I can give is: try it! I say this because some of my favorite lens/camera combinations are those with issues far beyond mere unsharpness, and that would likely be rejected by the mass of Internet forum cognoscenti in favor of native lenses that I know from experience that I'd never use even if I already owned them. Case in point: an old Arri/Zeiss 16mm f/1.2 cine lens that I shoot on Micro Four Thirds, despite the fact that it was designed for the much smaller 16mm (motion picture) format: in spite of edges are soft at all apertures, corners that aren't so much "soft" as "missing altogether", an overall image almost certainly less sharp than the average native kit zoom, and various other technical considerations compromising optical performance, I enjoy both the process of shooting with the lens and the results when I do. So why, then, should I give a damn what the Internet thinks? Whereas, I sold the more "appropriate" Panasonic 15mm f/1.7 native lens several years ago, at a considerable loss, for lack of use.

Sharlin 8y ago

For instance the archetypal modern nifty fifty, the Canon 50mm f/1.8 (any version) is tack sharp at f/2.8, and exceedingly so at f/4, but the larger apertures are... less than optimal. Including the center of the frame. There's readily visible halation (caused by ill-corrected spherical aberration?) that gives everything a soft, dreamy look, plus severe purple fringing around contrasty features (chromatic aberration). There are many recent lens designs that are tack sharp all over the frame already at maximum aperture, outresolving even a modern high-pixel-density APS-C sensor. But those have complex optical formulas and consequently are almost always large, heavy, and expensive. For instance, the extremely sharp Sigma 50mm f/1.4 A weighs 815 grams compared to the 290 grams of the venerable Canon 50mm/1.4, and the 130 grams of the plastic fantastic 50mm/1.8!