Canon EF 50mm f/1.4 USM - Full Format Review / Lab Test Report - Analysis
Lens Reviews -
Canon EOS (Full Format)
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The EF 50mm f/1.4 produces a slight to moderate amount of barrel distortion (1.1%). This is barely noticeable in
Ultra large aperture lenses have a hard time regarding vignetting when used on full format DSLRs. The EF 50mm f/1.4 USM shows an extremely high amount of light falloff at f/1.4 - a 2.7EV this is disturbing in most images unless you prefer the effect for artistic reasons. The issue improves substantially when stopping down to f/2 but you need to go for f/2.8 or beyond to reduce the light falloff to a degree where it isn't disturbing anymore.
The resolution chart shows a rather wide spread in image quality across the tested aperture range but this is typical for most ultra-large aperture lenses. The center performance is very good at f/1.4 but the borders are just on a good level and the corners are soft. The contrast level is also somewhat reduced especially towards the corners. The situation improves quite a bit when stopping down to f/2 - the center is lifted into excellent level here and the corners start to get acceptable. There's a further boost of the border/corner quality at f/2.8 - the outer region reaches very good figures here (albeit just). The range between f/4 and f/8 represents the sweet spot of the lens with an outstanding center resolution and generally excellent borders and corners. Diffraction effects reduce the global quality from f/11 onwards but this is, of course, a physical limitation and not a design issue of the lens.
Below is a simplified summary of the formal findings. The chart shows line widths
per picture height (LW/PH) which can be taken as a measure for sharpness.
If you want to know more about the MTF50 figures you may check out the corresponding
Chromatic Aberrations (CAs)
Similar to most other fix-focal lenses chromatic aberrations (color shadows at harsh contrast transitions) are
very low and nothing to worry about.
The bokeh (the quality of the out-of-focus blur) is a primary aspect for an ultra large aperture lens.
The out-of-focus highlights suffer somewhat from vignetting effects at f/1.4 so the shape does
deteriorate somewhat to a "cat's eye" towards the corners. There's also an outlining effect here but the inner
highlight zone is very smooth and uniform. The outlining is slightly improved at f/2 and it's gone by
f/2.8. However, starting at f/2.8 the highlights are no longer circular (thus the aperture is not circular
anymore). The quality of the blur in the critical focus transition zones is quite decent. It's
very smooth towards the foreground and still good (but slightly worse) towards the background.
Bokeh Fringing / Longitudinal Chromatic Aberrations (LoCA)
Bokeh fringing is a common problem present in most large aperture lenses and the Canon lens is no
exception to the rule here. If you look at the provided sample crops below you should be able to spot
a purple halo in front of the focus zone and a green one beyond. This is clearly visible at f/1.4 till
f/2. The problem starts to fade at f/2.8 and it's resolved at f/5.6.
Move the mouse cursor over the f-stop marks below to observe the respective LoCAs