How much smaller is a Twenty20 field than a normal ODI/Test field?
The same size. No difference. For any further info try out the link given below.
Why is the field of view under high-power magnification less than that under low-power magnification?
It is because you are expanding a smaller area. As you go higher in magnification, you are going to a smaller field of view and enlarging it so you can see it better.
Why does depth of field increase as you allow less light into the camera?
There are already some good bits of info above. Let me state it simply: depth of field doesn't have anything to do specifically with letting less light in. However, it DOES have to do with the size of the aperture. The smaller the hole, the greater t...