The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-50mm F2.8-4.5 DC OS HSM and the Carl Zeiss Distagon T2,8/21 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. Carl Zeiss Distagon T2,8/21 is the longer of the two lenses at 109mm. The Sigma 18-50mm F2.8-4.5 DC OS HSM with a length of 89mm, is 20mm shorter. Besides being longer, the Carl Zeiss Distagon T2,8/21 also has a larger diameter of 87mm compared to the Sigma 18-50mm F2.8-4.5 DC OS HSM'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 18-50mm F2.8-4.5 DC OS HSM weighs 395g, which means it is 205g (34%) lighter than the Carl Zeiss Distagon T2,8/21 which has a weight of 600g.
Filter Threads
The Sigma 18-50mm F2.8-4.5 DC OS HSM has a filter size of 67mm whereas the Carl Zeiss Distagon T2,8/21 has a 82mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 67mm filters that we recommend you to consider for the Sigma 18-50mm F2.8-4.5 DC OS HSM:
And these are the 82mm filters that we recommend for the Carl Zeiss Distagon T2,8/21:
Lens Mounts
The Sigma 18-50mm F2.8-4.5 DC OS HSM has the Nikon F (DX) lens mount whereas the Carl Zeiss Distagon T2,8/21 has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are Nikon D3500, Nikon D7500 and Nikon D5600 for the Nikon F (DX) Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Sigma 18-50mm F2.8-4.5 DC OS HSM is also available in the Canon EF , Pentax KAF3, Sony Alpha and Sigma SA mounts.
Carl Zeiss Distagon T2,8/21 is also available in Canon EF and Nikon F (FX) mounts.
Focal Range
Sigma 18-50mm F2.8-4.5 DC OS HSM has a focal range of 18-50mm and
2.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-75mm when used on a APS-C / DX format camera.
On the other hand, the Carl Zeiss Distagon T2,8/21 is a prime lens with fixed focal lenght of 21mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 31.5mm.
