Originally Posted by TomHuffman
First, I used Luv data and you used Lab data for dE calculations. These will yield slightly different results.
Second, it looks as though your calculations use the L data, which you should not for grayscale. All we are considering are the xy coordinates, so you should compare only the ab data for dE purposes. Normalize all of the L values (test and reference) at 100. The L data is used for primary/secondary color dE measurements, but not for grayscale.
Given these changes, here is your data and mine in an apples-to-apples comparison.
Third, the Spyder2 colorimeter is notoriously inaccurate, so it is hard to draw too many conclusions from these readings. You would be well-advised to purchase at least a X-Rite Display 2 LT, which performs much better.
Fourth, ignoring the previous point for a moment (or maybe because of it), your data does not support what you report that the center has a green blob. If anything, it is green deficient. The data says it should appear purplish.
Finally, after normalizing your data, the uniformity results are quite good, just a little worse than mine (3.7 vs. 2.2 average dE). However, the data shows a much larger deviation from D65, indicating that you need to tighten up your grayscale calibration. Even the center of the screen is 4.6 dE. Try to get that 2.5 or below.
Tom, thanks a lot for your help. A few things in response to your points...
1) Ok, didn't realize. Just kinda took a guess.
2) So I'm assuming you took my data, normalized the L values, and then back-calculated new x, y, R, G, and B values?
3) I heard the Spyder isn't the best. Perhaps I can get something better down the road, but I'll just have to work with what I've got for the time being.
4) I agree that this data doesn't completely support what appears to be a greenish blob. However, since it appears reddish all around the blob, it can be viewed as an absence of red in the middle if you look at it a little differently. The data shows MM to have the highest green level(although still less than 100%) and also one of the lowest red levels. This seems consistent with what I see.
5) Regarding my deviation from D65, I know I need some more work on the calibration. The numbers aren't as bad on average with your recalculation. However, shouldn't we look at the spread of dE values in addition to the average? Your highest value is 3.6 and I have 4 values higher than that including a 7.1 and a 6.7. Your standard devation is 1.2 while mine is 2.2. This also indicates more non-uniformity with a couple of regions being much worse than anything on your screen.
That's all I've got for now. Still trying to figure out what to do. I'll work on the calibration a bit more here sometime soon to see if that helps anything. I really don't want to exchange it for a set that's even worse or has other problems like dead pixels. But I also don't want to settle for something even slightly defective after spending so much money.
Thanks again! I'm enjoying trying to sort this out, but I wish there was nothing to sort out.