The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 10-18mm f4.5-5.6 IS STM and the Samyang 10mm f2.8 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 10mm f2.8 is the longer of the two lenses at 77mm. The Canon 10-18mm f4.5-5.6 IS STM with a length of 72mm, is 5mm shorter. Besides being longer, the Samyang 10mm f2.8 also has a larger diameter of 86mm compared to the Canon 10-18mm f4.5-5.6 IS STM's 75mm 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. Canon 10-18mm f4.5-5.6 IS STM weighs 240g, which means it is 340g (58%) lighter than the Samyang 10mm f2.8 which has a weight of 580g.
Lens Mounts
The Canon 10-18mm f4.5-5.6 IS STM has the Canon EF-S lens mount whereas the Samyang 10mm f2.8 has the Canon EF lens mount. Some of the latest released cameras that are compatible with these mounts are Canon T8i, Canon 90D and Canon SL3 for the Canon EF-S Mount and Canon T8i, Canon 90D and Canon SL3 for the Canon EF Mount.
Samyang 10mm f2.8 is also available in Canon EF-M , Fujifilm X, Nikon F (DX), Four Thirds and Micro Four Thirds mounts.
Focal Range
Canon 10-18mm f4.5-5.6 IS STM has a focal range of 10-18mm and
1.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
16-28.8mm when used on a APS-C / DX format camera.
On the other hand, the Samyang 10mm f2.8 is a prime lens with fixed focal lenght of 10mm which has an effective (full-frame 35mm equivalent) focal range of 16mm when used on a APS-C / DX format camera.