hi. i discovered something like 10 black spots on my s3 in total dark environment with dead pixel testing software while screen was total black. that's the only case you can see them. i checked my wife's s3 right after and had also black spots under same conditions.
the day after i checked my brother's s3 - same.
all of them have a few - i doubt if there is any display without. but why bother? do you ever have blank screen in black room? i found out with dead pixel testing, but i can’t trace them in any other case. Enjoy your phone and omit the insignificant - invincible - dots/patterns. i got over it after reading that is common and seeing the other two s3s. seeing your question i smiled understanding your worries of defective product
it's common so omit it.