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red color looks different over HDMI

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samer mahmoud
red color looks different over HDMI
on Jun 20, 2016 at 7:36:51 pm

hi, im facing a weird issue, when in davinci resolve, the red looks darker over HDMI signal feeding my HP Dreamcolor.
same monitor and same cable but when i output from premier using matrox rack2 the red is correct. as it should be, its how i see it on my Panasonic reference monitor over HD-SDI cable coming from both Matrox and DeckLink.

in matrox rack 2 utility, i can set the HDMI signal to YUV, maybe this is the problem, but i cant find where i can do this in Blackmagic design.

or do i need to convert the HDMI signal from Decklink to SDI signal?
hope someone can answer this soon. thanks


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Marc Wielage
Re: red color looks different over HDMI
on Jun 21, 2016 at 12:49:26 am

How is the monitor calibrated?

My opinion is that the Dreamcolors are not good enough for color correction, but that's me.


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samer mahmoud
Re: red color looks different over HDMI
on Jun 21, 2016 at 3:30:43 am

its calibrated using the Dreamcolor calibration tool, im planing to get FSI when i save some money. its only about 7000 i know, but to ship it over here (Lebanon) plus taxes, it will be like 10000$ :( i grade mostly music videos, so i guess its not worth to invest in FSI now thats why i went to HP, i seen lots of people using it for grading with decent results.

the signal coming out from the Matrox MXO2 Rack, is the same image i see on TV when my video is on broadcast.

my problem is with the signal coming from the Blackmagic design Decklink. and specially in Red channel, its too dark a bit looks wine color.

while from Matrox it looks pure Red, just as i see on Tv broadcast, as i see on my iphone, or any other computer screen or broadcast screen.

both signals HDMI signals. i was wondering if hdmi signal from Declink is not YUV so i need to go SDI out into mini converter to get HDMI out signal. just wondering.

NB, any advice of a low cost monitor that easy to be calibrated? i see recently people using panasonic plasma and add the SDI option to it.


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Marc Wielage
Re: red color looks different over HDMI
on Jun 21, 2016 at 6:20:45 am

Unfortunately, the HP calibration app is going to lie to you and not give accurate results.

You asked for advice -- I gave you advice. You can either believe me or not, but my opinion is still valid. The Dreamcolor was a cheap display made to give digital cartoon artists and VFX people a reasonable display for that application; it doesn't work well for Rec709 images, for a lot of reasons. It's great as a computer display; not great for making critical judgements for color.

Read this long, long discussion as to why it's not a good choice for color correction:

http://liftgammagain.com/forum/index.php?threads/new-hp-dreamcolor-monitors...

I think the Eizo CG-series are about as low-cost as you can get for Rec709 and still get reasonably reliable color, provided it's calibrated by a 3rd-party system like Light Illusion or Calman.


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samer mahmoud
Re: red color looks different over HDMI
on Jun 21, 2016 at 12:45:58 pm

Marc i believe and agree with you for sure, but since i already has it and cost me 1600$ (shipping + Taxes to Lebanon).

im trying to solve the problem. as i mentioned before, the monitor colors looks perfect on Broadcast, and the signal coming from Matrox card is correct (since its the same i see on TV when they broadcast the video. and almost the same on more than one devices)

my question is, why only the signal coming from the BlackMagic card looks different??? the red is dark with some blue to which gives it something between red and violet color.

note that when i connect the HDMI to a consumer monitor out from blackmagic, the red is normal. so its not the BM Decklink card, not the cable, the Dream color works fine with Matrox. so im assuming it might be the HDMI signal coming out of BM Decklink is RGB signal not YUV.
any idea if Decklink HDMI out is RGB or YUV ? if it was RGB, then i might only need HD-SDI to HDMI converter to Feed the monitor with YUV signal.


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Joseph Owens
Re: red color looks different over HDMI
on Jun 21, 2016 at 3:20:19 pm

[samer mahmoud] "ny idea if Decklink HDMI out is RGB or YUV "

You would have bigger problems if that was true. Because there is an apparent twist in the color cube where some hues are shifted in another direction, it is more than likely in whatever "calibration" table the Dreamcolor is using.

There really is only one way to improve the monitor's display fidelity and that is by coughing up for a reliable measurement tool and appropriate software. Its probably going to cost you another $1000 or so to get yourself a (minimum) X-Rite C6 spectrophotometer and either Light Illusion or the other manufacturer who triggers the nanny-filter on this forum. Even then, a pro-sumer-level display is going to take a couple of days' effort, thousands of measurements and fiddling around with the monitors "advanced" settings to get it close enough for the calibration tests to actually come up with something that isn't too far of a pre-distortion to generate the expected values without big discontinuities (banding) and noise.

"I always pass on free advice -- its never of any use to me" Oscar Wilde.


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samer mahmoud
Re: red color looks different over HDMI
on Jun 21, 2016 at 9:46:45 pm

Jo, the DreamColor is ok when im feeding it from Matrox MXO2, the problem is when i feed the Monitor from Decklink card, and when i feed a consumer monitor from Decklink via HDMI its ok, thats why i was thinking DeckLink HDMI out is only RGB or something that only works with consumer monitors not with the Dreamcolor which calibrated to rec 709 and using video levels.

i order blackmagic mini converter SDI to HDMI, i hope it works. im not welling to invest a high end grading monitor now, im only doing stuff for TV and my old panasonic was doing great job for few years before it pass away, and i had to act quick and get monitor for good price, but if this didnt work, now i have saved some, so i can get a better monitor, i heard about BON , not sure about the price, but they have a reseller here in Lebanon, wish FSI has. do you think the FSI AM Series? are they good enough for Grading? or i have to go into the CM series? if i could manage to get an FSI with a friend coming from USA.

sorry , too many questions :D you know how things get when you have a major issue and u want to fix quick :(


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