My example..I have and still use a Nikon D90. It works, takes great photos and works with all of my lenses so why not right?
Well the first thing to note is that I shoot in RAW format, meaning NEF files for the Nikon (Canon uses a CR2 format, Panasonic uses a generic RAW format) are going to be a different size as you get more megapixels. So my D90 takes RAW photos in about 10-11 megabytes per image. While my D7100 uses a 28 megabyte raw image. Your camera has a common raw file size average and you should know it.
Now…for my D90, I never use anything bigger than a 16GB SDHC card. Sure it will support a 32GB card but I get into a grey area I try to avoid.
If I have 28 GB worth of images on the card and it fails, I am going to be mad. However if I only have 7-10GB of photos on card, I will still be angry at the loss but it won’t be nearly as bad as with 32GB. See?
Now a word about speed. Most cards will put their fastest speeds on the card and that is usually the speed a device can READ from it. What you want are cards that sync up with your camera speed. If you shoot at 7 frames per second and have a 90MB/sec write speed on your card, you might be able to eek out a few more shots before your camera’s buffer for the number of images it can hold, runs out.
So..ignore that 250 MB/sec listing on the card and look up the write speed for that card. Odds are it is going to be less than the read speed for that card.
That’s a quick lesson. If you have questions, please let me know. Next time, the quickie lesson will be over picking lenses to take on a trip.