The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Samyang 300mm f6.3 and the Canon 400mm f5.6L USM 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. Canon 400mm f5.6L USM is the longer of the two lenses at 257mm. The Samyang 300mm f6.3 with a length of 74mm, is 183mm shorter. Besides being longer, the Canon 400mm f5.6L USM also has a larger diameter of 90mm compared to the Samyang 300mm f6.3's 65mm 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. Samyang 300mm f6.3 weighs 260g, which means it is 990g (79%) lighter than the Canon 400mm f5.6L USM which has a weight of 1250g.
Below you can find the dimension and weight table of the Telephoto Mirror Prime Lenses in Canon EF Mount for size comparison purposes.
Super Telephoto Lenses in Canon EF Mount for Size Comparison
The Samyang 300mm f6.3 has a filter size of 26mm whereas the Canon 400mm f5.6L USM has a 77mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 26mm filters that we recommend you to consider for the Samyang 300mm f6.3:
And these are the 77mm filters that we recommend for the Canon 400mm f5.6L USM:
Both the Samyang 300mm f6.3 and the Canon 400mm f5.6L USM has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon T8i, Canon 90D and Canon SL3.
Samyang 300mm f6.3 is also available in Nikon F (DX) , Four Thirds and Sony Alpha mounts.
Samyang 300mm f6.3 is a prime lens with fixed focal lenght of 300mm which has an effective (full-frame 35mm equivalent) focal range of 480mm
when used on a APS-C / DX format camera.
On the other hand, the Canon 400mm f5.6L USM is a prime lens with fixed focal lenght of 400mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 640mm.