I have lately tested Sony GM 24-70/2.8 against Sigma 24-70/2.8 and Sony GM 70-200/2.8 versus 100-400/4.5-5.6.
Sigma is a clear winner in every respect (sharper across the frame with better corners,especially at 24 and 70mm.Contrastier,less LoCA and LCA,smaller,lighter,cheaper).It has however pronounced distortion at 24mm and loud clunking from the insight when shaken only after 2000 shots approximately.Also there is a bit of a longitudinl loose on the zoom ring,but zoom doesn't creep and all feel tight.
I still consider keeping GM 24-70 for it's colour rendition,smooth oof blurr and solid built.A very decent lens overall it is,but seems slightly dated on a 42 MPX FF sensor.
GM 70-200/2.8 is a tad less sharp and contrasty compared to GM 100-400 within overlapping focal lengths,showing bit more LoCA,but has constant f2.8,that I need and has similar performance to 100-400,so I bought it.
Looking at an Anhinga with wings open basking in the sun.
Cropped, tripod mounted 200-600mm G set to 600mm and A7rIII camera; silent shutter.
ISO 400, f6.3, 1/2000 second.
December 6, 2020
Along Lake Apopka Wildlife Drive, Apopka, FL.
