The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Samyang 85mm F1.8 ED UMC CS 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. Samyang 85mm F1.8 ED UMC CS is the longer of the two lenses at 81mm. The Sigma 90mm F2.8 DG DN C with a length of 60mm, is 21mm shorter. Besides being longer, the Samyang 85mm F1.8 ED UMC CS also has a larger diameter of 68mm compared to the Sigma 90mm F2.8 DG DN C's 64mm diameter.
Samyang 85mm F1.8 ED UMC CS 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, 14% (49g) lighter than the Samyang 85mm F1.8 ED UMC CS's weight of 344g.
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 Samyang 85mm F1.8 ED UMC CS has a filter size of 62mm 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 62mm filters that we recommend you to consider for the Samyang 85mm F1.8 ED UMC CS:
And these are the 55mm filters that we recommend for the Sigma 90mm F2.8 DG DN C:
Lens Mounts
Both the Samyang 85mm F1.8 ED UMC CS 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 A6700, Sony FX30 and Sony ZV-E10.
Samyang 85mm F1.8 ED UMC CS is also available in Canon EF-M and Fujifilm X mounts.
Sigma 90mm F2.8 DG DN C is also available in Leica L mount.
Focal Range
Samyang 85mm F1.8 ED UMC CS is a prime lens with fixed focal lenght of 85mm which has an effective (full-frame 35mm equivalent) focal range of
127.5mm when used on a APS-C / DX format camera.
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.