There is no good answer to that. It would depend on what gamma you are after, and on your particular display. A gamma of 2.2 is the de facto standard, but if you have a really bright room, or a truly pitch black room, you might want something different. Also since one Quattron isn't the same as another Quattron, even if it came off the line right before it, you can't take the setting from another display and assume it is correct. Setting gamma almost always requires instruments, as it's not something you can eyeball, even using a test pattern, and really get right.