Preorders: Tamron 50-40mm FE at BHphoto, Adorama. in EU at Fotokoch, FotoErhardt, Calumet, WexUK.
SonyAlphaBlog reviewed the new lens and concluded:
Compared to the Tamron:
- Sony E 70-350mm F4.5-6.3 G OSS : 900 Euros, lighter , less range less good optically
- Sony FE 100-400mm GM OSS F4.5-F5.6 (2900 euros) : Similar Sharpness performances but better AF for erratic movements and compatible with TC1.4 TC2.0 and 30fps of the A1, more buttons for direct controls , but more heavy and pricy. Less versatile as 100mm is often too long for some portraits or street photography
- Sigma 100-400mm F5-6.3 DG DN OS Contemporary (1000 euros). Sharpness is less good , AF is less good
When to choose the Sony : If you are only shooting fast sports with very complex movements and also need 30fps or needs very precise smooth zooming, or need the TC 1.4 or TC2
In all other cases the Tamron optical and AF performances being very close to the Sony and offering unique versatility for Portrait, street, travel with its zoom range of 50-100mm
The Sigma should be chosen only for lower Mpix camera (24/33Mpix) and if you are on a limited budget