Received my Tamron 17-70mm today...

BeatX wrote:

Thx for sharing Your opinion

Uhh.. That Tamron 17-70/2.8 is big! I mean it looks like similar size to any 24-105/4 FF zoom lenses (?) for me personally standard zoom lens of this size for APSC camera is wired idea. Beside VC (and Fuji color science), there is very little adventages of such huge lens attached to Fuji camera, where You Can get for example R6 + 24-105/4 IS L lens in similar size compared to X-T4 + T17/70/2.8. And You got all adventages of FF sensor, plus better AF.

The Tamron 17-70 weighs 525g, the Canon 24-105 weighs 700g, the Sony 24-105 weighs 663g, and the Nikon 24-120 weighs 630g. All are similar in length.

This makes sense because f/2.8 on APS-C gives the same total light collected as f/4 on FF and hence similar image quality*. There can be some weight saving in APS-C due to the smaller image circle requiring smaller glass elements. The 3 FF lenses have 77mm filters while the Tamron has 67mm, indicating smaller diameter glass. So it is 105g - 175g lighter.

There is no IQ advantage of a FF sensor with a f/4 lens compared to an APS-C sensor with a f/2.8 lens.* The slower lens cancels the advantage of the larger sensor. The advantage of FF comes when you put a f/2.8 lens on it. But then it's big, heavy, and expensive.

When I chose a mirrorless system I compared a Fuji system with f/2.8 zooms with the Nikon FF system with f/4 zooms. The total system weight and size was very close. The Fuji system should have been a bit lighter but was handicapped by the excessively heavy 16-55 f/2.8.

*The exception is when both systems are at base ISO and same exposure - then the FF collects a stop more total light and will have a 1 stop IQ advantage.