Conclusion: The Canon EF 50mm F1.4 USM may be based upon a 37-year old optical design, but its performance in our studio tests clearly shows that it's not giving up yet. Sure the hairs are beginning to grey a little, and Sigma's new young pretender can outmuscle it comprehensively at wider apertures, but this lens really shows its quality once the aperture is closed down a couple of stops.
Pros: Excellent image quality when stopped down, Essentially no lateral chromatic aberration, Fast and accurate autofocus with full-time manual override
Cons: Distinctly soft and 'dreamy' at wider apertures (F1.4-F1.8), Bokeh chromatic aberration, most visible at wide apertures, Vignetting at wide apertures on full frame (essentially disappears by F2.8), Somwhat susceptible to flare
Excerpt: Canon's 50/1.4 is a bit heavier than the 50/1.8 but it gives you simultaneous AF/MF because of its USM focusing motor . It is one f-stop slower than the 50/1.0 but much lighter weight and less than one-sixth the price. If you are going to limit yourself to one 50mm prime lens, this is the natural choice.
Summary: Canon EF 50mm f/1.4 USM should probably be considered the best alternative among Canon's four 50mm lenses (in terms of value for the money, overall performance and capabilities). While not as fast as its more expensive 50mm f/1.2L USM variant, this lens performs as well (if not better) pretty much throughout comparable aperture range.
Excerpt: Ask a bunch of photographers what their favorite lens is - and you will likely hear the Canon EF 50mm f/1.4 USM Lens mentioned. It is sharp, small, light, inexpensive and with an f1.4 aperture, fast .
Summary: Although not pin-sharp at its widest apertures, Canon’s EF 50mm f/1.4 USM remains a competent performer and its image quality between f/4 and f/8is excellent. Two issues should be considered when assessing this lens: the size of the sensor on that camera with which it will be mainly used and whether the types of images you take will be affected by the inherent imperfections in reproduction.
Conclusion: The Canon EF 1.4/50 USM is undoubtedly a well-done lens. The picture quality in the frame centre and at the edges is very good at apertures above f/2.0 – you can count it among the biggest assets of this device, apart from the solid workmanship. You should notice, though, that there were several slip-ups during the test.
Cons: by f/1.4 the image is distinctly „soft”,, very high coma,, susceptibility to flares,, visible distortion on full frame,, very high vignetting on full frame.