CurtPalme.com Home Theater Forum

AFryia · Posted: Sun Feb 01, 2009 8:38 pm Post subject: Gamma Control via HTPC ?

Anyone out there using either their video card software or Powerstrip to modify/correct their gamma?

I have my PJ setup with very good gray scale and contrast ratio but have some black crush. Sad

Zebu Fellenz · Joined: 21 Dec 2006 Posts: 2567

Gamma on my Geforce 7950gt via Nvidia Control Panel.

Works fine and doesn't seem to elevate black levels.

Software is Powerdvd 7.3 for HD-DVD and Blu-ray.

AFryia · Posted: Sun Feb 01, 2009 9:09 pm Post subject:

I have an older video card ATI 9800Pro. The Catalyst software has what appears to be RGB gamma control. I have PowerStrip which has what appears to be RGB gamma control. And then there is a software program a forum member wrote for modifying the LUT table.

Is there any preference where you modify the gamma? At the card, software, or LUT table?

AFryia · Posted: Sun Feb 01, 2009 9:16 pm Post subject:

While on the subject.

Is there a way with a colormeter to measure the gamma response of each tube then come up with an inverse response table?

Angus_rg · Posted: Mon Feb 02, 2009 12:12 am Post subject:

Fredrik · Joined: 03 Jul 2007 Posts: 49 Location: Stockholm

Got the same question as Afryia.
How would one go about adjusting/measuring gamma ?

David_Web · Joined: 02 May 2007 Posts: 418 Location: Sweden

"At the card, software, or LUT table?"
It's all the same as far as I am aware. All methods use the LUT.

I would not use Powerstrip as it has a bad rounding error that causes severe banding. At least the version I use. Not sure if there is a newer version. And don't use it to store curves ether as it has the same error there.

Not sure how the newest cards handle their built in functions but I doubt it's better than a well setup LUT.

Fredrik · Joined: 03 Jul 2007 Posts: 49 Location: Stockholm

I was thinking of doing it via software, "Levels" of FFDSHOW, not sure how good it is though.

AFryia · Posted: Wed Mar 04, 2009 2:02 am Post subject:

Well I played with the LUT table and was able to get some decent results. I haven't done a lot of critical viewing but so far so good.

benareeno · Joined: 22 Mar 2006 Posts: 1614 Location: ottawa, canada

so this means we can simply edit the LUT table and try to get a custom gamma curve??

How do we do it?

AFryia · Posted: Thu Mar 05, 2009 1:52 am Post subject:

benareeno · Joined: 22 Mar 2006 Posts: 1614 Location: ottawa, canada

where is the lut file?

akajester · Joined: 09 Jul 2008 Posts: 934 Location: Wisconsin

AFryia, can you let us know what software you used and the methods to correct your gamma issues? I'm having some luminance issues on the upper end and my gamma drops way low. I'd like to correct it on the htpc.

thanks!

AFryia · Posted: Sun Jun 21, 2009 12:10 am Post subject:

I'm using an early version of PCGG that was offered as freeware on the other site. I also use VideoEqualizer for viewing. PCGG uses a table form which is easy for inputting adjustments to modify the LUT. VE is graphical which is good for viewing the results not as easy for modifying the LUT. I use HFCR software with the DIY colormeter.

In PCGG you enter your display's measured 100% IRE luminance value and target gamma. PCGG then gives a target luminace for each IRE step. You then put up an IRE grey scale pattern and adjust the RGB LUT for grey scale tracking and target luminance. You have to do it iteratively other wise you will get banding.

akajester · Joined: 09 Jul 2008 Posts: 934 Location: Wisconsin

Thanks, I'll check that out, sounds like fun! Smile