I recall the "rule" of using the reciprocal of the length of a lens as its minimum shutter speed ( 100 mm = 1/100). What I am having a difficult time understanding is WHY this would change from crop sensor to full frame.

I guess my difficulty in understanding this is what would be the relationship since the length of the lens has not changed. Light would not act any differently on the lens in either case. The difference would be how the sensor interprets the light, not how the lens impacted it.

A good exposure and focus would be the same with the lens on either sensor.

Perhaps, I am missing something or just plain misunderstanding some relationship. I hope some of our learned members can help clear this up.

Speed matters if you shoot in bursts for sure... especially if you shoot raw since the files are so much bigger.

The faster the camera can write to the card the faster it empties the buffer, and the faster the camera can continue to shoot.

I shoot with a D7100, which has a small buffer, the D7200 from what I have heard has a bigger buffer, so it can shoot faster for longer then it needs to write the buffer to the card, so the faster it writes the faster it empties the buffer and the longer & faster it can continue to shoot in a burst.

If you only look at the CLASS rating you will miss out on fast cards as the CLASS rating ONLY refers to a minimum speed (CLASS 10 cards have at least a speed of 10 MB/S) - so a card that writes at 10 MB/s is CLASS 10 AND a card that writes at 20 MB/s is also CLASS 10...

Get beyond CLASS rating and look at actual speeds - look for WRITE speed, not necessarily read speeds....

I use Samsung Pro cards in my D7100, quite fast, 32 GB in size and were cheap enough at the time to make them the best bang for the buck - a good site to find real speed tests & costs for cards is:

http://www.cameramemoryspeed.com

For the D7200, see this page:
http://www.cameramemoryspeed.com/nikon-d7200/sd-card-comparison/

Note: This has to do with point-and-shoots cameras only, not dSLRs.

We've had multiple point-and-shoot cameras that eventually get what looks like sensor dust or dirt spots on photos. Cleaning the lens does not help. These seem to be inside.

These involved multiple makes and models of point-and-shoots, and not necessarily very low-end ones. Mine cost a few hundred dollars.

Any idea on cures or even causes?

We live in Florida, which I understand can cause some odd problems not seen be most others.

TIA

Digital photography has created a new and rather miraculous form of capturing images by allowing us to stitch together hundreds, even thousands of images, that have the potential of revealing with great accuracy vast views. At present, we use the word "stitch" or "photomerge" but it would be better to have a proper term that is also flexible for creating additional terms from it. We have in English a word from ancient Greek that means "stitch", as in "rhapsody", which means "stitched song". After thinking about it for a while, even consulting with a great philologist (my friend Robert Lamberton), we came up with the term "photorapsy" that resembles photography and may also provide the adjective "photoraptic" or even the noun "photorapter", like photographer" and a verb "to photorapt".
Opinions and suggestions for discussion are welcome.
Sarantis