The Tamron 15-30 close focus distance is 9cm from all the mucking about I've done last night. Tamron state 28cm in the specs. Likewise the Sigma 35mm is specced at 28cm too but it is able to focus at 16cm.
With this in mind I figured I'd do a quick test (and because I wanted pics of the cpl filter for MM anyway
![Stick Out Tongue :p :p](/styles/default/xenforo/vbSmilies/Normal/tongue.gif)
) to see detail and bokeh difference at f2.8 between both lenses.
Sharpness wise was much of a muchness, Tamron say the lens delivers prime class sharpness, I found it only a hair less sharp than the Sigma 35 1.4 @ 2.8, though the 9cm close focus distance allows for slightly increased magnification even with the extra 5mm compensating on the Sigma.
A bit more vignette out of the box on the Tamron at 30mm, none on the Sigma at 2.8. LR lens profile corrects that on the Tamron 100%, I didn't apply any though, just straight export.
I have not yet seen any CA or fringing on the Tamron.
Impressed!