moving photos to an SD card for picture frame viewing

I do the classic steps, created desktop folder, transferred photos to folder - - but when I try to drag that folder into the SD card in finder it refuses to transfer. What am I doing wrong?

Can you tell us what format the SD card is using and how large it is? Also, what is the total size of the photos you're trying to move to the SD card?

The SD is MS DOS (FAT), 2GB. I'm moving 30 photos stored in an album. Don't know if this is a factor, but when I go into the disc utility the format dropdown is greyed out and inoperative.

Two things occur to me:
1. Does the SD card have a tab that locks it so you can't write to it?
2. Do the photos need to be in a folder? That may not be necessary for this frame but it is hard to say without knowing the model.

Thanks for your suggestion. Feeling pretty dumb. When I inserted the SD and went to disc utility and erase or partition tab, it said "read only" - - - finally tried removing the card, sliding the lock take back/forth several times - - then, carefully reinserted into iMac. It worked. I conclude, as I slide in the SD I am catching the lower part of the slot and sliding the lock tab, or SD lock is defective. It's working. Thank you

You're welcome. That was a complete shot in the dark by the way. If anyone asks though I'm suggesting it was genius on my part. I'd appreciate it if you back me up on that.