The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 135mm F1.8 DG HSM and the Sigma 90mm F2.8 DG DN C 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 135mm F1.8 DG HSM is the longer of the two lenses at 141mm. The Sigma 90mm F2.8 DG DN C with a length of 60mm, is 81mm shorter. Besides being longer, the Sigma 135mm F1.8 DG HSM also has a larger diameter of 91mm compared to the Sigma 90mm F2.8 DG DN C's 64mm diameter.
Sigma 135mm F1.8 DG HSM vs Sigma 90mm F2.8 DG DN C Lenses Size Comparison
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 90mm F2.8 DG DN C weighs 295g, 73% (835g) lighter than the Sigma 135mm F1.8 DG HSM's weight of 1130g.
Below you can find the dimension and weight table of the Telephoto Prime Lenses in Sony E Mount for size comparison purposes.
Telephoto Lenses in Sony E Mount for Size Comparison
Filter Threads
The Sigma 135mm F1.8 DG HSM has a filter size of 82mm whereas the Sigma 90mm F2.8 DG DN C has a 55mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 82mm filters that we recommend you to consider for the Sigma 135mm F1.8 DG HSM:
And these are the 55mm filters that we recommend for the Sigma 90mm F2.8 DG DN C:
Lens Mounts
Both the Sigma 135mm F1.8 DG HSM and the Sigma 90mm F2.8 DG DN C has the same Sony E lens mount. Some of the latest released cameras that are compatible with the Sony E lenses are Sony A9 III, Sony A7C Mark II and Sony A7CR.
Sigma 135mm F1.8 DG HSM is also available in Sigma SA , Nikon F (FX) and Canon EF mounts.
Sigma 90mm F2.8 DG DN C is also available in Leica L mount.
Focal Range
Sigma 135mm F1.8 DG HSM is a prime lens with fixed focal lenght of 135mm.
On the other hand, the Sigma 90mm F2.8 DG DN C is a prime lens with fixed focal lenght of 90mm which has an effective (full-frame 35mm equivalent) focal range of 135mm when used on a 35mm FF format camera.