what should I set gamma adjustment to?

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.

You can NEVER tell what the best gamma control setting is without a meter and calibration software and the knowledge about how to use it. No setting any other owner is using is going to necessarily be the right setting for your room and your TV. If you have 6 owners who say they are using +1 and seven owners are using 0 and six owners are using -1... but if none of them have meters and calibration software, all you are getting is 20 guesses. All the settings they are using have a chance of being right, but there's a bigger chance they are wrong.

This sort of thing is why people get TVs calibrated... either by paying for a professional calibration, or by purchasing a meter, calibration software, and a calibration disc and teaching themselves how to calibrate (which takes maybe 100 hours of study and practice before you get your first good calibration).

Calibration is the only way to know that your settings are as accurate as they can be. There may still be errors after calibration, because some TVs simply don't have controls that are capable of removing all errors. But, calibration will insure that any given TV is as accurate as it can be made given the design and controls that are available.

In addition to what Doug said, let's say you want the setting closest to a 2.2 average gamma. On one sample of this TV model/screen size, the optimal setting for 2.2 gamma might be +1. On another sample, it could be 0 or -1. My point being that you cannot assume all samples of a given model/make/screen size will perform identically.

To make things even more confusing, there's no "one" measured gamma value either. It varies from black to white.

For example, you may have a gamma of 2.2 near white but closer to 3 near black such as this picture.



In the picture above the solid yellow line is gamma "after" calibration while the dotted yellow line is "before" calibration. The white line is the target. The cyan line is the average.

Kal

In that case, the gamma near black is most critical while changes in the top end (and even midrange) will be much less visible (using power law gamma).

All true.

As someone who has calibrated a bunch of Quattrons,I can confidently say a setting of +2 is not in the right direction. I always end up with a setting between -2 and 0, with most being at -2 or -1.
On Quattrons I normally target a gamma average between 2.3 and 2.4. Some models have a 10 pt WB/gamma adjustment to further refine the gamma, and some do not.

I think I just heard a pop! which must be the OPs head

I agree with Chad on the gamma settings for the Sharp Quatrons.

That gamma curve in the graph post calibration looks quite good. Clearly not good prior to calibration.