Here's my understanding . . . . .
The Class 4 cards will "work", but they may not work well if you take advantage of some of the more recent features of newer cams. What I'm talking about is programming the cam to take lots of pics (or video) quickly, with only a short "time out" between triggerings. The Class 4 card may not be able to "record" as fast as some settings allowed by the camera.
When digital cams were first becoming popular, many would not allow a triggering any more frequently than 1 minute, and might not even allow but 1 or 2 pics per triggering event.
Many of today's cams will allow for say 7 pics per single triggering event, and the "triggering" can be programmed for only 5 seconds or less between those "7-pic" events. You need a "fast" card to take advantage of this capability.
Personally, I'm still using a lot of old Class 4 cards, but generally limit their use to my older cams. Recent purchases of SD cards have only been the Class 10 Sandisk "Ultra" fast ones. When you purchased SD cards (say at Walmart), most of the 16gb and higher capacity cards seem to be Class 10, with the "Ultras" being a bit more expensive (but all very cheap compared to a few years ago). Most of the 8gb and lower capacity seem to be Class 4 (at least by my observations).
One issue is some still-working older cams won't take anything larger than an 8gb SD card (regardless of "class"), and I don't want to purchase any new cards that are not Class 10 and "ultra" fast for the newer cams. Heck, next year's cams may need a Class 20 super-ultra. :mrgreen:
