Reply To: A really great read…

[nesgran]

A longer lens will give a more diffusely blurred background than a short lens with the same DOF. This is simply because of the magnification of the background, the longer the lens the less background will be smeared around the back. This is why the 200mm f2 will provide more blurred backgrounds than the 85mm f1.2 despite the 85mm giving a shorter DOF at the same framing. This is also another reason longer macro lenses are a good idea. In CC’s comparison shots with the painted faces you can also see the bokeh advantage of the full frame camera. It isn’t massive but it does equate to 1 1/3 stops. The bigger sensor will also collect 1 1/3 stops more light leading to better noise performance. If you look at comparisons between the Canon 1D MkIII and 40D who both share the same generation sensor, same chip and same megapixel count the larger sensored 1D comes out on top by more than a stop better noise performance. In this case probably helped slightly by the better electronics of the 1D but also but the 2/3 stop advantage in light gathering.

CC, I think your ruler experiments come out a little funny because the 150mm lens is acting a little shorter than the 100mm. If it had been nikons it would be fine but with the 1.6x crop of canons (not to mention the subtle differences in focal length between different lens models).

A full frame camera will always have the edge when it comes to performance, not by a massive amount but you simply can’t argue away the physics.