Hi,

Yet another question from me, and this time it's about gamma.

When calibrating a pioneer gen. 6 plasma, I end up with a gamma of 2.14. With the gamma option set to 1, which gives me the highest gamma.

My question is: Can I do anything else to raise the gamma level, say: in the grayscale adjustments or somewhere else.

So far the only way I could change the gamma number is to change the preset that's in the user menu.

Is 2.5 the "magic number" for plasma also?

Thanks,

Dimitri

If you're using calibration software that produces a gamma curve, take a look at it and note where your actual luminance numbers go above the target curve. You'll want to get those areas as close to the target curve as possible, most likely by lowering contrast and/or brightness.

Thx royce,

But that doesn't seem to help, gamma stays the same.

When I compare it to the target it's not far off but a gamma of 2.5 is desirable isn't it?.

Dimitri

Thx royce,

But that doesn't seem to help, gamma stays the same.

When I compare it to the target it's not far off but a gamma of 2.5 is desirable isn't it?.

Dimitri

The "correct" gamma is usually based on your lighting conditions. A lot of people use 2.2 as a comprimise for all types of viewing. So somewhere in the 2.2-2.5 should be good.

My question is: Can I do anything else to raise the gamma level, say: in the grayscale adjustments or somewhere else.

Be very careful when trying to calibrate out gamma issues. We, obviously, recommend people look at the gamma values for each measurement point when making adjustments. Looking at one number that is an average or a curve fit can hide the introduction of picture-killing issues when you are making adjustments (e.g., I can raise your low-end gamma significantly, killing your shadow detail, to give you a higher overall gamma number, but the overall picture quality will have gone down).

Barring having a package that gives you detailed data on gamma, you will want to use carefully selected test material (e.g., lots of shadow detail, highlights) to make sure you haven't made things worse, rather than better, when calibrating gamma.

Bill

Thanks guys

:) :) :)

along these lines I have a question about the VP50 gamma adjustments- what do they do to the image. i have a Sony 1292 CRT projector feed 1080p60 via HDMI (moome hdmi card) and when I test the gamma it is around 2.12 or so. Yet playing with the Gamma adjustments on the vp50 only makes it worse (say like 1.8 gamma). Shouldnt the gamma increase make it closer to 2.5? Should I only do one color at a time (i was doing red, green, and blue the same amount) ?


It seems that with a CRT (I usually calibrate lcd and plasmas with our Sencore kit) that the 10, and 20 IRE boxes are very off (like 5400k). yet the middle of the greyscale 30-60 tracking is very blue (7500-8500k). How do i get the curve to be more uniform, and closer to 6500k across the board? I am not sure what IRE's to calibrate with on a CRT projector. 10 is soooo dark I think the CP5000 is not accurate at that low light. Should I use 30 and 70 or 20 and 80 or what do you guys think?


Thanks a lot in advance,

Jon

You can adjust gamma with the RGB cut-off and drive controls.
Although these controls are primarily for grayscale balance they also adjust luminence.

The correct approach is to calibrate for d.65 at both the high and low points and then adjust the individual RGB controls the same amount in theory affecting luminance and maintaining colour balance. You make luminance conform to the required aim for a given gamma at that IRE point ( mapped to your balck and white points). Some displays even have "all cuts" "all gain" controls to facilitate this. ( panny plasmas have this for example)

However in the real world adjusting all RGB values by the same incriment will pull the overall D.65 balance out of whack as well as increase luminance so you will constantly have to readjust slightly as the luminance increases.
You'll get the luminance target for your high and low adjustment points from looking at something like Calman ( a while since I used it) or by using a gamma calculator ( accuracy dependant on how well its been written and whether it employs a transform function or a simple gamma model)

. Should I use 30 and 70 or 20 and 80 or what do you guys think?


Thanks a lot in advance,

Jon

I usually try 20 and 80. If 20 won't read reliably ( and I doubt it will be a problem to be honest) go to 30. You may also find you get better results by varying the adjustment points (30 and 70 might give better all round tracking than 20 and 80 for example). It will depend on the display but I usually start with with 20 and 80 and then have a look at the resulting curves.

Thanks