Here is a summary of some additional measurements I've made. An example of each pattern type (22 sets of 10%-100% stimulus sequences except full-fields[23]) are in the attached pngs. It took about an hour to go through all the patterns with my D3. The display and meter were allowed to warm-up for an hour before measurements and repeat measurements were made to assess probe uncertainty. Note that absolute accuracy is irrelevant for these measurements, we only care about stability and sensitivity from start to finish.

For comparison, all of the measurements are referenced to an average of patterns 3,7,12,17. Chromaticity shifts are calculated using the dE(u*v*) formula with L*=100. Gamma shifts are calculated and averaged over the range 20%-40% as that is where the largest shifts are observed and this range is also important for perceived contrast.

I've termed the reference xyY values the Operating Range average (ORavg). These are the standard 10% windows with black surround, 10% APL, 22% APL, and 35% APL. I chose these to define some sort of baseline against which all the patterns can be compared and outliers can be eliminated using a "consensus" approach. Hopefully the consensus will be consistent with previous assumptions about calibrating with patterns that simulate actual usage.

The first plot I made looks at the power load characteristics using three different measurements.

The blue curve is the %Luminance drop of the peak white pattern in sets 1-21. You can see that there is no indication of power loading in these patterns to within a couple of percent up to the maximum APL that was used (35%). The green curve is the power loading as measured using a variable area peak white pattern [set #22] and shows that this pattern starts loading down the display above 25% APL stimulus. The red curve was derived from full field measurements and referenced to the luminance of the ORavg. This curve shows us two things, first there is a luminance depression throughout the 10%-50% stimulus region. This is the effect we've seen plotted in other ways previously and leads to the gamma shifts. We also see that it recovers and does not show the typical ABL loading until average APL is greater than 50%. Why the difference between the red and the green curves? This is because in terms of power draw it's not the average stimulus that we need to look at but the average luminance.

Here is the same data plotted against average luminance.

This doesn't change any conclusions about the stability of the power circuit over the range these patterns were run (the blue curve is still well within the overall stable region) but it does point out that a constant APL stimulus does not imply a constant power draw on plasmas. If the area of the window used to construct the pattern is held constant, the average luminance over a 10 step pattern set

So the first thing I looked at was the chromaticity shifts relative to the ORavg. The error bars in the figure were calculated as the +/- 1-sigma deviation of dE(u*v*) from an average of 6 repeated measurements of pattern set #1. The six measurements included one done at the beginning of the run and one done at the end.

The JND of this dE formula is 3 and you can see that there is only one pattern set that is at that level (barely) and also statistically significant. These were the full field patterns[#23]. This agrees with Tom's previous findings although the dE values on this display are somewhat smaller. This pattern set is the only one I can eliminate from consideration based on chromaticity shifts.

edit: Thanks to Tom I have fixed an error in my dE calculation which show more outliers in the data set. The peaks in this plot [1,10,15,19] are all 1% windowed patterns on fixed backgrounds and along with the full field patterns[23] show the largest shifts relative to ORavg. It's interesting to note that 1% patterns on multilevel backgrounds do not show this behavior.

The error bars for measuring gamma shifts were calculated from the same repeated measurements as above. In the plot below, positive gamma is low relative to the ORavg while negative is high[gamma shift=ORavg gamma-measured gamma]. The pattern numbers are generally arranged from lowest APL to highest except for the following:

1. Pattern #1 and #19 is my control pattern [1% area/25% APL]

2. Patterns #20,#21 are Chronoptimist's patterns which got added in late.

In this plot you see the separation as shown earlier in other plots between the low APL/low gamma response and higher APL/higher gamma response. The maximum shift is 0.17 between 1% on black background and full field patterns. You can also see higher variability among the black background [2-8] vs. fixed APL patterns. So given this plot I would choose the more stable patterns which are shifted negative relative to the ORavg in order to weight the calibration toward typical APL averages. Of those patterns the tightest grouping are the ones which use 10% area windows. I found that the 1% windows yielded lower gammas [see patterns #9,#15] indicating that regardless of the APL very small window sizes show a luminance boost. In addition I think you would find that 1% constant luminance areas are in the minority in real video content compared to larger areas. Anyone have isoluminance maps of average video levels?

Other considerations:

The data indicates no differences outside of the error bars between a random, fixed, or even the still image background I chose at random, to form the fixed APL level of the pattern for gamma calibration. Some dependence on multilevel vs. fixed backgrounds was seen in the chromaticity shifts of 1% windowed data. I would recommend a multilevel background in keeping with the "calibrate as you use" philosophy

Given this data set, for

I would also recommend this pattern set for

patpg1.png 43k .png file

patpg2.png 93k .png file

patpg3.png 137k .png file

patpg4.png 20k .png file

Raw data used in calculations.

gammatest_raw.xlsx 16k .xlsx file

Edited by zoyd - 6/24/12 at 1:42pm

For comparison, all of the measurements are referenced to an average of patterns 3,7,12,17. Chromaticity shifts are calculated using the dE(u*v*) formula with L*=100. Gamma shifts are calculated and averaged over the range 20%-40% as that is where the largest shifts are observed and this range is also important for perceived contrast.

I've termed the reference xyY values the Operating Range average (ORavg). These are the standard 10% windows with black surround, 10% APL, 22% APL, and 35% APL. I chose these to define some sort of baseline against which all the patterns can be compared and outliers can be eliminated using a "consensus" approach. Hopefully the consensus will be consistent with previous assumptions about calibrating with patterns that simulate actual usage.

The first plot I made looks at the power load characteristics using three different measurements.

The blue curve is the %Luminance drop of the peak white pattern in sets 1-21. You can see that there is no indication of power loading in these patterns to within a couple of percent up to the maximum APL that was used (35%). The green curve is the power loading as measured using a variable area peak white pattern [set #22] and shows that this pattern starts loading down the display above 25% APL stimulus. The red curve was derived from full field measurements and referenced to the luminance of the ORavg. This curve shows us two things, first there is a luminance depression throughout the 10%-50% stimulus region. This is the effect we've seen plotted in other ways previously and leads to the gamma shifts. We also see that it recovers and does not show the typical ABL loading until average APL is greater than 50%. Why the difference between the red and the green curves? This is because in terms of power draw it's not the average stimulus that we need to look at but the average luminance.

Here is the same data plotted against average luminance.

This doesn't change any conclusions about the stability of the power circuit over the range these patterns were run (the blue curve is still well within the overall stable region) but it does point out that a constant APL stimulus does not imply a constant power draw on plasmas. If the area of the window used to construct the pattern is held constant, the average luminance over a 10 step pattern set

*will*change even if the average stimulus is fixed.So the first thing I looked at was the chromaticity shifts relative to the ORavg. The error bars in the figure were calculated as the +/- 1-sigma deviation of dE(u*v*) from an average of 6 repeated measurements of pattern set #1. The six measurements included one done at the beginning of the run and one done at the end.

The JND of this dE formula is 3 and you can see that there is only one pattern set that is at that level (barely) and also statistically significant. These were the full field patterns[#23]. This agrees with Tom's previous findings although the dE values on this display are somewhat smaller. This pattern set is the only one I can eliminate from consideration based on chromaticity shifts.

edit: Thanks to Tom I have fixed an error in my dE calculation which show more outliers in the data set. The peaks in this plot [1,10,15,19] are all 1% windowed patterns on fixed backgrounds and along with the full field patterns[23] show the largest shifts relative to ORavg. It's interesting to note that 1% patterns on multilevel backgrounds do not show this behavior.

The error bars for measuring gamma shifts were calculated from the same repeated measurements as above. In the plot below, positive gamma is low relative to the ORavg while negative is high[gamma shift=ORavg gamma-measured gamma]. The pattern numbers are generally arranged from lowest APL to highest except for the following:

1. Pattern #1 and #19 is my control pattern [1% area/25% APL]

2. Patterns #20,#21 are Chronoptimist's patterns which got added in late.

In this plot you see the separation as shown earlier in other plots between the low APL/low gamma response and higher APL/higher gamma response. The maximum shift is 0.17 between 1% on black background and full field patterns. You can also see higher variability among the black background [2-8] vs. fixed APL patterns. So given this plot I would choose the more stable patterns which are shifted negative relative to the ORavg in order to weight the calibration toward typical APL averages. Of those patterns the tightest grouping are the ones which use 10% area windows. I found that the 1% windows yielded lower gammas [see patterns #9,#15] indicating that regardless of the APL very small window sizes show a luminance boost. In addition I think you would find that 1% constant luminance areas are in the minority in real video content compared to larger areas. Anyone have isoluminance maps of average video levels?

Other considerations:

The data indicates no differences outside of the error bars between a random, fixed, or even the still image background I chose at random, to form the fixed APL level of the pattern for gamma calibration. Some dependence on multilevel vs. fixed backgrounds was seen in the chromaticity shifts of 1% windowed data. I would recommend a multilevel background in keeping with the "calibrate as you use" philosophy

*when testing displays with unknown linearity characteristics.*Given this data set, for

**plasma**calibration I would opt for 10% by area windows on a multilevel fixed background designed to yield 22% constant APL.I would also recommend this pattern set for

*any*display technology in the sense that if you obtain different settings using this set compared to standard windows, these use a more theoretically defensible metrology approach. As everyone knows in most cases such differences will be very small. This data is good example of both arguments. The chromaticity shifts in the grey scale do not warrant switching from standard to APL on this display but the gamma shifts do.patpg1.png 43k .png file

patpg2.png 93k .png file

patpg3.png 137k .png file

patpg4.png 20k .png file

Raw data used in calculations.

gammatest_raw.xlsx 16k .xlsx file

Edited by zoyd - 6/24/12 at 1:42pm