The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Kamlan 55mm F1.2 and the Sony FE 40mm F2.5 G for their suitability to various photography scenarios:
Size and Weight 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. Sony FE 40mm F2.5 G weighs 173g, 75% (527g) lighter than the Kamlan 55mm F1.2's weight of 700g.
Below you can find the dimension and weight table of the Standard Prime Lenses in Sony E Mount for size comparison purposes.
Standard Lenses in Sony E Mount for Size Comparison
Filter Threads
The Kamlan 55mm F1.2 has a filter size of 62mm whereas the Sony FE 40mm F2.5 G has a 49mm 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 Kamlan 55mm F1.2:
And these are the 49mm filters that we recommend for the Sony FE 40mm F2.5 G:
Lens Mounts
Both the Kamlan 55mm F1.2 and the Sony FE 40mm F2.5 G 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.
Focal Range
Kamlan 55mm F1.2 is a prime lens with fixed focal lenght of 50mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
75mm.
On the other hand, the Sony FE 40mm F2.5 G is a prime lens with fixed focal lenght of 40mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 60mm.