Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Sony 12-24mm F2.8 GM is the longer of the two lenses at 137mm. The Sony FE 12-24mm F4 G with a length of 117mm is 20mm shorter. Besides being longer, the Sony 12-24mm F2.8 GM also has a larger diameter of 98mm compared to Sony FE 12-24mm F4 G's 87mm diameter.
Below you can find the scaled side by side image of Sony 12-24mm F2.8 GM and Sony FE 12-24mm F4 G to get a better idea of how their size compare in real life.
Weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Sony FE 12-24mm F4 G weighs 565g, 49% (282g) lighter than the Sony 12-24mm F2.8 GM's weight of 847g.
Below you can find the dimension and weight table of the 'Wideangle Zoom Lenses in Sony E Mount for size comparison purposes.
Wideangle Zoom Lenses in Sony E Mount for Size Comparison
Both Sony 12-24mm F2.8 GM and Sony FE 12-24mm F4 G has the same Sony E lens mount. Some of the latest released cameras that are compatible with the Sony E lenses are Sony A7 IV, Sony ZV-E10 and Sony A1.