Secrets Q & A
- Written by Christian Eberle
- Published on 24 November 2008
- Professional Display Calibration: What It Is and What It Means to Your Home Theater Experience
- Page 2: Anatomy of a Professional Display Calibration
- Page 3: What Will Professional Display Calibration Do For Me?
- Page 4: THX and the Imaging Science Foundation (ISF)
- Page 5: Sample Data from a Calibration
- Page 6: Conclusions About Professional Display Calibration
- All Pages
Sample Data from a Calibration
Below are some sample graphs from a Panasonic AE2000U LCD projector. These will give you an idea of what happens during a professional calibration. The calibrator can provide these charts to a client to show what has been done to the display. These graphs are produced by the color analyzer software. They are not specific to THX or the ISF. They are meant to show the before and after state of a display.
Here (below) are the measured primary and secondary color points from a Panasonic AE2000U front projector before calibration of the Color Management System. The triangles represent the measured points and the circles represent the SMPTE color space for HDTV. You can see that red and blue are close to the standard, but green is oversaturated. Also the cyan secondary is phased too much toward blue. While the color is not too bad, green will look a bit unnatural (like grass for example), and flesh tones will be a tad off because of the error in the cyan secondary.
Now take a look at the measured color points from the same projector after calibration of the Color Management System. All points are nearly perfect except for yellow. In this case, getting yellow right meant sacrificing accuracy on cyan and magenta. This result represents the best compromise, getting the most points correct. It is not always possible to achieve a perfect CIE chart with consumer displays.
This graph shows the Panasonic AE2000U projector before grayscale calibration. This is the warmest color temperature preset. Not only is the tracking poor, it is too warm as well. This would show up as reddish whites in bright scenes and reddish blacks in dark scenes. Only the midtones are close to correct.
And here is the AE2000U after grayscale calibration. Now the tracking between 30 and 80 IRE is very consistent and only a touch above D65. The spikes at 20 and 100 IRE are not visible to the eye, only the color meter. Now all shades of white down to minimum black will have the proper neutral look.
Once levels are set correctly, gamma is the next most important component in creating an image with maximum dynamic range. The AE2000U's out-of-the-box gamma is illustrated below. The brightness increases too quickly out of black (the target gamma of 2.20 is shown in the green line, and the measured gamma is the blue line). This creates a washed out look in dark scenes. Even though the black level might be set correctly, the image will lack depth and dimension with this gamma curve.
Below is the corrected gamma curve of the same AE2000U. Now the quality of blacks and dark scene material will be much better. Getting the gamma curve right really makes the image pop and look more three-dimensional.