Any thoughts on LCD screen calibration and gamut coverage against colour temperature

[ajohnw]

@John,

A DeltaE of 2.2 is still below the general threshold of 3 that is the level where you can see a difference. But if you can see it and it really bothers you then it may be that your monitor is the culprit. Fixing it will then become expensive.

Alex

The 2.2 error still shows a noticeable brown tint to the red. I would hope to do better.

I have finally found out why many calibrators wont work well on LED back lit monitors. It seems ( ie read on the web) that all but a few of the newer ones do not calculate the white point accurately and read it low by 400 to 600K. This does fit in with the readings I have obtained in the monitors built in standard modes using a MonacoOptrix. This substantially increases the cost of an upgrade to a LED back lit monitor. 2 calibrators that will work are the new Spyder4 and the ColorMonki Display. Both have 2 types of LED back light settings. RGB and white leds. They also have the usual LCD and CRT settings. I have ordered a ColorMonki as they seem to be offering field upgrades if similar problems crop up with more changes in this area which I think is very likely especially on wide gamut displays. It seems spectrometer type calibrators are still ok but I suspect these may have marginal problems as well given how they function.

It's worth noting this as there is a good crop of used colorimeters and spectrometers on ebay at the moment. I have only seen one listing where the seller states that the colorimeter wont calibrate a LED type display. Personally I wouldn't be tempted to buy a used spectrometer. Often over twice the cost of a new colorimeter and no guarantee in respect to it's current state of calibration.

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[ajohnw]

Finally sorted and it looks like the Viewsonic VP2365 LED Professional does deserve the title. The sRGB gamut coverage is a little low at 95% but I suspect more calibration work might get that to the usual 98%. The problem I had was mostly down to selecting black point compensation in the software. The low level response is not linear as show by this curve. Correcting the red throws all of the mid brightness colours way out especially red.



The end results of the calibration are as follows. The higher delta E error are all now related to slight brightness variation rather than colour errors.

Grey Scale etc



Colour Delta E



The dynamic range comes out at 615:1. I suspect this will mean that when I look at contrast and brightness setting grey scales that the just able to see last white step will be clearer than the last step in the black end.

Had fun installing the white led back light compensation for the colormunki display colourimeter used. The software has an option to import corrections from other colourimeter software. Auto may have worked. Not sure but select file and pointing that at the install program on the x-rite disk did. These then had to be found and added using the colourimeter compensation bar. I expected them to appear in the display type selector. They probably will at some point. I went for the ColorMunki because they mention field upgrades for future display types. These are likely. The software that comes with it works but doesn't have any mechanism for seeing what has actually been achieved. Few colour patches are used for the calibration as well. Takes about 5mins as against 50 using this software.

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