I've been pleased with the performance of the Tamron SP 24-70/LA-EA3 combo, but for me it's just too big and heavy to use as a carry-around zoom. And because I don't shoot weddings or events, f/2.8 is pretty much lost on me. On the rare occasions I shoot any kind of portraits, I've got a nice 85mm f/1.8. So I bought the Sony 24–105 to see if it could replace the Tamron. And soon after I got it I started testing the two against each other. So... The Comparo First, I set up a 70mm shot of a distant landscape. I set the aperture at f/4 because I figured that the lenses would be fairly equal by f/8 or so. The camera (A7RII) was on a sturdy tripod, IBIS off, manual focus (on Pilot Rock), and a 2-sec timer. These are from raw images straight out of Lightroom, with only the lens profiles applied. No other processing. Here are some 100% crops (Tamron left, Sony right), of the center: and the lower left corner: Then I did the standard bookshelf test at both 24mm and 70mm, again at f/4. Just a closeup of the upper right here. And again, Tamron left, Sony right. 24mm 70mm And finally I wanted to do a test of the way I shoot a lot; 24mm, auto-focus, hand-held, IBIS on, f/8. Then I did a little exposure and contrast adjustment in Lightroom, and synched those adjustments between the Tamron and Sony shots. Left side And center I weighed the two lenses on my postal scale, and with the adapter the Tamron was 992g, the Sony, 737g. That extra 35mm of reach is very welcome, and if the IQ degrades at 105mm, I can't see it. So that Tamron's gone to eBay.