The Sigma 50mm ƒ/1.4 was designed to accommodate the 35mm film frame, and is available for all SLR camera mounts: Canon, Nikon, Sony/Minolta, Pentax and Four-Thirds. On Canon sub-frame sensor bodies the lens provides an effective field of view of 80mm; on Nikon the field of view is effectively 75mm; and on Four-Thirds subframe bodies, the field of view is effectively 100mm.
The Sigma 50mm ƒ/1.4 is available now for a street price of under $500.
For the most part, the Sigma 50mm ƒ/1.4 is a sharp lens. However, there are some very notable exceptions. Let's take a closer look.
On the sub-frame Canon 20D, when shot wide open at ƒ/1.4 the lens produces images that are just slightly soft - between 2 and 3 blur units across the frame. Stopped down to ƒ/2 and sharpness improves dramatically, now showing results between 1 and 2 blur units, and further improvement shows at ƒ/2.8. Image sharpness peaks at ƒ/4 and stays there until ƒ/11, where we see numbers that still stay below 2 blur units. At ƒ/16 we still note very good performance, with an average performance of around 2 blur units.