Originally posted by Adam The depth of field at the same focal length never changes, regardless of sensor format.
However, when comparing larger sensors to smaller ones, you'll indeed get less depth of field at the same angle of view with the larger sensor. Let's take a focal length of 24mm on full frame and 18mm on aps-c as an example. Both will deliver the same angle of view, but the full frame lens will have less depth of field since it's a longer focal length.
Yes, I like this explanation.
Depth of field is affected by focal length and aperture size. The sensor / film simply faithfully record what is projected on them.
Larger sensor / film requires longer focal length to create a projection size that will cover them, therefore, you get the effect of using a longer focal length, which we perceive as shallower depth-of-field.
But when we're talking about the total package (i.e the whole camera), it's not wrong to say that we indeed get pictures with more depth of field using APS-C cameras given that we're talking about the same aperture setting.