This is to be expected, as I can confidently say after testing that the G Master is night and day better than the f/4 G version. The G version is also smaller in every dimension: Φ3.43” x 4.62”. I don’t have a Sony 12-24mm f/4 G lens to visually compare, but specs-wise, it’s significantly lighter only weighing 565g. Sony does have a 12-24mm f/4 G version as previously stated, but the quality and slower aperture have been a little lacking for the type of photography that I do (mainly landscapes and astrophotography). This is where the new 12-24mm f/2.8 GM comes into play I can now pack 3 G Master quality lenses and cover a massive focal length range from 12mm to 200mm. The quality of the 16-35mm f/2.8 is just about immaculate, but having that much focal length overlap with the 24-70mm f/2.8 just hasn’t made sense for me. Sony’s 16-35mm f/2.8 GM lens is moderately lighter weighing 680g with dimensions of Φ3.48” x 4.79”, making it more tempting to pack in my backpack.
It’s also a bit longer and wider at the front coming in at Φ3.875” x 5.5” versus Φ3.45” x 5.35” for the 24-70mm f/2.8. The new 12-24mm f/2.8 weighs in at 847g, making it slightly lighter than the 24-70mm f/2.8 at 886g. At a glance, this lens looks and feels very similar to the Sony FE 24-70mm f/2.8 GM.