If APS-C and similar crop-sensor digital cameras have a focal length multiplying effect such that a 50mm lens has an apparent focal length closer to the field of view of an 80mm on a full frame camera, and yet at the same time the depth of field for the smaller sensor camera is more like the depth of field a 50mm lens would produce on a full frame camera (using the same aperture), then this would seem to suggest the concept of an "aperture dividing effect."

In other words, a 50mm f/1.8 lens on an APS-C camera would act more like a 80mm f/2.8 (approx. 1.8 * 1.6x) lens in 35mm equivalent — for depth of field, not considering exposure.

Can someone with a better understanding of the physics involved clarify this for me.  I've never seen this concept explicitly mentioned anywhere, so I am a bit suspect of it.


Question: Difference between busses
Answer: This smells like a homework assignment.  In any case, it should be easy to look up some introduction to each of these busses and then compare them.  However, briefly:

IDE is a parallel bus used primarily inside computers to communicate with disk drives.  It is carried on ribbon cables 2-3 inches wide.

SATA is the replacement for IDE.  It is high speed serial, so uses a lot fewer wires.

PCI is the bus you physically plug I/O cards into in a PC.  These are the cards with the tall thin metal faces that provide connections out the back via the "I/O slots".  For example, you can get add on ethernet "cards" if you want your PC to have more than the one network connetion the comes on the motherboard.

USB is for external devices.  Surely you've heard of this unless you've been living under a rock for the last 20 years.



As for compare and contrast, this is your homework assignment, not mine.