Quote Originally Posted by neuroanatomist
At 1:1 magnification, you're at the MFD regardless of sensor size, so that's 30 cm (11.8") from the sensor. On the 7D at f/8, your DoF would be 1.8 mm, while on the 5DII at f/8, your DoF would be 2.9 mm (i.e. 1.6x deeper DoF with FF).

But 1:1 on the 7D gives you a smaller field of view than 1:1 on the 5D. To compare apples to apples (ie, compare taking the same picture with two different sized sensors), you should compare 1.6x magnification on the 5DII with 1x on the 7D.


Quote Originally Posted by neuroanatomist
So, it's a triple advantage to FF for macro shooting.

The way I see it, there is *no* advantage either way. Let me explain.


In macro shooting, you never seem to have enough DOF. You can stop down, but this leads to diffraction. So the question should be, suppose I want to take the same picture of a given small subject (eg, the picture is 15mm across along the focal plane) and I want to stop down to get a given DOF (say 2mm). How much resolution do the rules of diffraction allow? The answer to this question is independent of sensor size. Ie, if you stop down more with the FF camera so that DOF is the same, diffraction limited resolution will be the same (by this I mean the airy disk will be proportional to sensor size, giving resolution which is independent of sensor size).