The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Venus 25mm F2.8 2.5-5X Ultra Macro and the Sigma 105mm F2.8 EX DG Macro 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 105mm F2.8 EX DG Macro is the longer of the two lenses at 98mm. The Venus 25mm F2.8 2.5-5X Ultra Macro with a length of 65mm, is 33mm shorter. On the other hand, the Venus 25mm F2.8 2.5-5X Ultra Macro has a larger diameter of 82mm compared to the Sigma 105mm F2.8 EX DG Macro'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. Venus 25mm F2.8 2.5-5X Ultra Macro weighs 400g, which means it is 60g (13%) lighter than the Sigma 105mm F2.8 EX DG Macro which has a weight of 460g.
Lens Mounts
The Venus 25mm F2.8 2.5-5X Ultra Macro has the Pentax KAF2 lens mount whereas the Sigma 105mm F2.8 EX DG Macro has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF2 Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Venus 25mm F2.8 2.5-5X Ultra Macro is also available in the Canon EF , Nikon F (DX) and Sony E mounts.
Sigma 105mm F2.8 EX DG Macro is also available in Canon EF , Nikon F (FX), Sony Alpha, Sigma SA and Four Thirds mounts.
Focal Range
Venus 25mm F2.8 2.5-5X Ultra Macro is a prime lens with fixed focal lenght of 25mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
37.5mm.
On the other hand, the Sigma 105mm F2.8 EX DG Macro is a prime lens with fixed focal lenght of 105mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 157.5mm.
