I see alot of people are recommending tamron 17-50mm f2.8 vs kit lens 18-55mm for canon and the main reason was because of the constant aperture F2.8. (Leaving aside the IQ and performance of this lens)
They often quoted that F2.8 is good for low light situation. My understanding is that aperture is more for DOF, no doubt we can use F2.8 at dim lighted area but wont the picture throw out shallow DOF?
For example, if i were to shoot indoor for a large group photo, would F2.8 become useful? What about night shooting of landscape with very minimum lighting at F2.8?