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PS50Q97HDX Plasma Calibration

by Vincent Teoh
24 May 2007

Baseline CCT (Correlated Colour Temperature)

As with most Samsung flat screen TVs we have tested recently, the "Movie" mode on PS50Q97HDX generated a baseline CCT that was closest to 6500k:

Precalibration CCT Precalibration RGB

Calibrated CCT

"Movie" mode also presented further white balance controls, which I used to achieve D65 greyscale without accessing service menu:

50Q97 CCT 50Q97HD RGB

Baseline Colour Chromaticity

Auto CIE Wide CIE

Samsung PS50Q97HDXBuy this for £617.47 at Dixons
Use code '5TV' for £32.50 discount
offered 2 colour space options: "Auto" and "Wide". The former (CIE chart on the left) displayed primary colour points that were very close to the REC 709 high definition standard, while the latter (CIE on the right) was more saturated especially in green primary to make sporting events look more vibrant (though not necessarily accurate).

Calibrated Colour Chromaticity

Needless to say I started calibrating the colours on Samsung PS50Q97HDXBuy this for £617.47 at Dixons
Use code '5TV' for £32.50 discount
with colour space set to "Auto" given its commendable primary chromaticities. Adjusting the secondary colours proved to be trickier: yellow and cyan were quite far off their respective points yet magenta was almost spot on. Because "Tint" control rotated all 3 secondaries around a central axis, aligning any one of them entailed sacrificing one or two of the others. "Colour" affected the saturation globally; while "My Colour Control" altered the saturation of individual hues in a subtle fashion both visually and measurably – on the CIE diagram only "Green" brought about a small change between 0% to 75% saturation of green primary.

After some tweaking and measuring, this is what I ended up with:

PS50Q97HDX CIE

Lab Test Results

Dead pixels 3 subpixels (2 blue, 1 red)
Screen Uniformity "Reflection moire"
Overscanning on HDMI, Component 2.5 percent (Just Scan corrects for HDMI)
Blacker than black Passed
Black level Excellent
Black level retention Stable with DNIe off
Primary colours Very good using "Auto" colour space
Scaling Average
Video mode deinterlacing Average, limited jaggies reduction
Film mode deinterlacing 3:2 cadence passed with Movie Plus on
Viewing angle Excellent
Motion blur Minimal but for processing issue
Digital noise Hardly any at 8 feet
Sharpness Defeatable edge enhancement

Dead Pixels

2 blue and 1 red subpixels were found dead on the top one-third of the screen. These are not uncommon among flat panels, and manufacturers usually have a tolerance of around 5 dead pixels (depending on their location) before an affected screen can be declared faulty for the purpose of return/ exchange. Even from 1 feet away I couldn't pick them out so I doubt they would impair real-world performance from normal sitting distances, but this is one instance where fussy owners can exercise their right under Distance Selling Regulation in their quest to find a blemish-free screen.

Screen Uniformity

Our Samsung PS50Q97HDXBuy this for £617.47 at Dixons
Use code '5TV' for £32.50 discount
suffered from a strange screen uniformity problem (if it can be classified as such) that I haven't seen before on any other HDTVs. Here's a photo shot:

Reflection Moire

Whenever there's enough ambient light shining on the Samsung PS50Q97HDXBuy this for £617.47 at Dixons
Use code '5TV' for £32.50 discount
, I detected slightly curved horizontal lines running across the screen especially in areas where there was very little light output from the TV itself. These lines were not static: they became denser as I walked closer to the screen, and moved up and down in line with my vision. Wrapping the ferrite cores around the power and signal cables did nothing to ameliorate this problem.

I believe this is an unwanted side effect of the Ultra Filterbright™ anti-reflection film installed behind the plasma glass, causing what I term as "reflection moire". This is my theory: the Ultra Filterbright™ scatters external light in such a manner that it interacts with the glass, leading to inteference patterns ("moire") that exist only in our visual perception... sort of an optical illusion if you like.

My theory explains why the configuration of the lines vary according to your visual distance and angle (if the lines were fixed then a physical defect is more likely), and why they go away when there's little ambient light reflecting off the screen. It may also be why I didn't see the lines in brighter areas of the screen – internal light originating from the Samsung PS50Q97HDXBuy this for £617.47 at Dixons
Use code '5TV' for £32.50 discount
would have overridden the reflected ambient light.

I really want to put my hand on my heart and say that these horizontal lines did not bother me, but I can't. As a reviewer I'm extremely sensitive to what's happening on screen, and it's hard not to notice these lines. It is sadly ironic that Ultra Filterbright™ has been designed to improve the usability of Samsung PS50Q97HDXBuy this for £617.47 at Dixons
Use code '5TV' for £32.50 discount
under bright conditions, yet to eliminate this artifact one would almost certainly need stringent room light control.

Video Processing

As expected, unless "Movie Plus" was enabled, Samsung PS50Q97HDXBuy this for £617.47 at Dixons
Use code '5TV' for £32.50 discount
could not lock on to 3:2 cadence for proper film mode deinterlacing. This means that you may see jaggies, twitter, moire and other artifacts when watching NTSC, HD DVD or Blu-ray in interlaced mode, although the higher the resolution of the source material the less visible these artifacts are.

Turning on "Movie Plus" will solve this issue, but add Samsung's own frame interpolation technology to the mix. In place of deinterlacing artifacts, you will see the motion on screen being sped up a bit. It's best to experiment with various source material to see if you like this effect, but personally I cannot tolerate "Movie Plus" as it mutates the 24p cinematic aura into an "amateur video" feel.


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