Hi guys,

I was wondering if someone can give me some advise regarding probe placement on a flat TV screen. I have a Pioneer 5080HD and use HCFR with a Eye-One Display LT. Normally, I pop the i1 on the middle of the screen and let it warm up for 30 minutes. Last night, I noticed that all my readings for Red were 3% lower than from a previous session. After checking my setup to no avail, I moved the probe an inch and the Red readings were 100% again.

Some questions:
1) What is the best practice when placing a probe on a flat screen? Should I be measuring multiple spots on the screen for the correct spot? How would I know which spot is correct?
2) Will another probe like Chroma 5 resolve this issue?

Plasma panels typically have poor flat field uniformity which is what you can attribute the discrepancy in measurements of you Pioneer panel to. Typically you should measure dead-center on the screen as this is where your eye will be focused the majority of the time.

Plasma panels typically have poor flat field uniformity which is what you can attribute the discrepancy in measurements of you Pioneer panel to. Typically you should measure dead-center on the screen as this is where your eye will be focused the majority of the time.

Thanks for the reply. I guess I am making this issue more complex than needed. But the problem is I thought I was placing the probe in the middle in both cases. :o It makes me wonder about some of the meter comparisons and if the probes were on the "exact" spot.

Plasma panels typically have poor flat field uniformity
This comment runs contrary to everything I've experienced and read about displays. It's my understanding that plasmas have superior flat field uniformity, since each red, green and blue pixel is energized individually, and no optical correction or manipulation is necessary. What do you really mean by this statement? On its face, I would have to disagree. Plasmas are certainly better at flat field uniformity than direct view CRTs (due to the varying angle of incidence of the electron beam), all projection systems (due to the optics and angle of incidence to the screen surface), and most LCDs (due to the grid of cold cathode fluorescent backlight tubes). Would you please elaborate? Perhaps you mean uniformity as it relates to the specific instrument mentioned, rather than as it relates to the viewer?

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.

"Advancing the art and science of electronic imaging"

George you are not clear on what flat field uniformity is as noted in your post. What we are trying to say is that all of the pixels in the Raster pattern (full field) are not the exact same color of Grey. This is partly due to the fact that the panels when adjusted at the factory are corrected in "zones" which are not all evenly matched to one another. Furthermore each pixel may not have identical performance when driven by a signal causing the display to have a non-uniform appearance. This lack of uniformity is visible typically only when displaying patterns from a generator or test disc. The uniformity issues will not typically be visible when displaying program matter unless you are carefully observing the panel for this phenomenon.

If you put any level of Gray pattern on a plasma panel (full field/Raster) you will definitely see that the image is not uniform edge to edge top/bottom or left to right.

There's nothing confusing or complex about flat field uniformity. It's simply the consistency of color and brightness across the entire screen, side to side, corner to corner, etc. There are exceptional examples of good uniformity in every display category, but in general, I've seen superior uniformity from the samples of plasmas I've encountered.

Alan, if I had to presume, my belief is what you are considering is that when measuring Footlamberts at various points around a (good) panel (as we do in one of the ISF seminar labs) the measurements are all very close to one another.

My interpretation of what Cliff is saying is that, while Ftl. are similar, Grayscale measurement, especially with the new Progressive Labs "giant killer", reveals more dissimilarities than one suspects from the panel composition and factory adjustment (not service menu) that he mentions.