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issue with LCD? - near-whites get pink tint at max contrast

 
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Arcsaber



Joined: 15 Apr 2015
Posts: 16



PostLink    Posted: Tue May 05, 2015 6:44 pm    Post subject: issue with LCD? - near-whites get pink tint at max contrast Reply with quote


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Just finished (re) calibrating my Sammy H6400, and despite the 10-point greyscales all coming in under 1.0 and a smooth gamma curve, I noticed something odd when checking some contrast patterns.

When above-white material is present, the 90+ near-whites take on a pink tinge, as do whites next to yellows. I am running the contrast at 100 - I watch most of my telly at night so black levels are more important to me than max luminance; 100 contrast with 7/20 backlight gives me 0.047/106 nits.

Is this just red clipping? The dE at full-field 90 and 100 IRE is only 0.1 and 0.4 respectively, but there's a definite (slight - no more than 2%) red "hump" around the near-whites between 90 and 100. If no above-white material actually comes through in normal usage, it shouldn't be a problem; the OCD in me just wants to know what's going on:).

Also, is there any danger in running a panel at max contrast?
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Arcsaber



Joined: 15 Apr 2015
Posts: 16



PostLink    Posted: Wed May 06, 2015 11:57 am    Post subject: Reply with quote

Further to my last post, here's the gamma curves for the setup in question - definite red clipping, it'll have nose-dived between 90 and 100 if we could see it:



This is odd; every other display I've seen has run out of blue by the end!
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HogPilot



Joined: 21 Jan 2010
Posts: 2383


TV/Projector: Vizio P702ui-B3, Pioneer Elite Pro-151FD & 111FD


PostLink    Posted: Wed May 06, 2015 12:08 pm    Post subject: Reply with quote

No danger in running your LED at max contrast. Would be a different story if you had a plasma display.

Are you 100% positive that the dip in red happens above 90% only when you have WTW material present on the screen? I could understand if the WTW stuff appeared off, but for it to affect lower levels is definitely odd. Could it just be a perceptual thing - i.e. the presence of "off" whites makes the surrounding stuff look wierd?

Not saying that what you've described isn't happening, but would it be possible for you to use a grey ramp with above 100% to take some actual measurements of your 90% and 100% white balance with and without WTW present?

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Arcsaber



Joined: 15 Apr 2015
Posts: 16



PostLink    Posted: Wed May 06, 2015 12:29 pm    Post subject: Reply with quote

As it happens, I found a "near white" sweep facility in the lastest version of HCFR so I ran that - the red component rose to 106% at 94 IRE, then dropped back down to 100% at 100 (but my red slider was maxed-out on the 100 IRE WB control...). No above-white present in those.

I've since backed things off a bit - contrast down to 90, with a bit more backlight to reach 100+ nits; just had to sacrifice some black depth. Gamma curves are now all parallel; max near-white dE is now 0.6.
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