Quote - @BB, would the discrepancy in render Gc and monitor Gc make a difference?

(I'm not BB, but...)
It would make no difference to the render output. The only difference it would make is to display things slightly brighter on Esther's own screen (if she's using 1.8) than on ours (using 2.2).

Esther, as a matter of interest, are you on Snow Leopard? If so, your default display gamma setting is already 2.2.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)