The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Irix 45mm F1.4 and the Sigma 50mm F1.4 DG HSM A for their suitability to various photography scenarios:
Size and Weight Comparison
Weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Sigma 50mm F1.4 DG HSM A weighs 815g, 11% (110g) lighter than the Irix 45mm F1.4's weight of 925g.
Below you can find the dimension and weight table of the 'Standard Prime Lenses in Canon EF Mount for size comparison purposes.
Standard Prime Lenses in Canon EF Mount for Size Comparison
Lens Mounts
Both Irix 45mm F1.4 and Sigma 50mm F1.4 DG HSM A has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon 1D X III, Canon 6D MII and Canon 5D MIV.
Irix 45mm F1.4 is also available in Nikon F (FX) and Pentax KAF2 mounts.
Sigma 50mm F1.4 DG HSM A is also available in Sony Alpha , Sigma SA, Nikon F (FX) and Leica L mounts.
Focal Range
Irix 45mm F1.4 is a prime lens with fixed focal lenght of 45mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides an 35mm (FF) equivalent of 72mm.
Sigma 50mm F1.4 DG HSM A is a prime lens with fixed focal lenght of 50mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides an 35mm (FF) equivalent of 80mm.