The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 20mm F1.8 EX DG RF and the Sigma 15mm F2.8 EX DG Fisheye for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Sigma 20mm F1.8 EX DG RF is the longer of the two lenses at 90mm. The Sigma 15mm F2.8 EX DG Fisheye with a length of 65mm, is 25mm shorter. Besides being longer, the Sigma 20mm F1.8 EX DG RF also has a larger diameter of 89mm compared to the Sigma 15mm F2.8 EX DG Fisheye's 74mm diameter.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Sigma 15mm F2.8 EX DG Fisheye weighs 370g, 28% (150g) lighter than the Sigma 20mm F1.8 EX DG RF's weight of 520g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Sigma SA Mount for size comparison purposes.
Ultra-Wideangle Lenses in Sigma SA Mount for Size Comparison
Lens Mounts
Both the Sigma 20mm F1.8 EX DG RF and the Sigma 15mm F2.8 EX DG Fisheye has the same Sigma SA lens mount. Some of the latest released cameras that are compatible with the Sigma SA lenses are Sigma Quattro, Sigma Quattro H and Sigma SD1 Merrill.
Sigma 20mm F1.8 EX DG RF is also available in the Canon EF , Nikon F (DX), Pentax KAF and Sony Alpha mounts.
Sigma 15mm F2.8 EX DG Fisheye is also available in Canon EF , Nikon F (FX), Pentax KAF and Sony Alpha mounts.
Focal Range
Sigma 20mm F1.8 EX DG RF is a prime lens with fixed focal lenght of 20mm.
On the other hand, the Sigma 15mm F2.8 EX DG Fisheye is a prime lens with fixed focal lenght of 15mm.
