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Author Topic: Nikon D810 Monitor Calibration -- waste of time?  (Read 1087 times)

Roger_Breton

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Nikon D810 Monitor Calibration -- waste of time?
« on: November 22, 2018, 05:37:37 pm »

Been a while since I posted here.
Experimenting with a Nikon D810.
Under the Setup Menu, there is a "Monitor Color Balance" option.

I thought, naively, that this "thing" can be calibrated in a "device-independent" way.
For those of you who are familiar with the D810 and this option, the procedure is simple.
It will default to the last image taken but any image in the memory card can be selected.

I thought I'd use some kind of neutral gray card but I ended up using the GretagMacbeth White Balance card.
So I shot the card by a window in the house.
Sky was overcast. I thought "blue"?

Next thing I did is to measure the "White Balance Card" as displayed on the camera.
I got : 6709 K (x 0.3102 y 0.3219) at 64.56 cd/m2.

I thought, wow! Close to D65?

So I continued my little experiment.
This morning, the sky was clear and I was able to photograph the card under Direct Sunlight.
I got: 6546 K (0.3108 0.3408) at 81 cd/m2.

Odd?

10 minutes ago, I decided to make a last attempt under Tungsten light.
I got: 3991 K at 75 cd/m2.

Ideally, I'd like to set the Monitor Balance one way and leave it that way.
I don't intend to use the Monitor to judge color but the human spirit is what it is...
I was thinking, perhaps, to set it for "Direct Sunlight", close to D50, the more "natural" condition for photography.
But I could equally set it on D65.

What bugs me is that it seems to be "contextual"?
If the "Color Balance" in the selected image is close to D65, it will use its estimated white point to display the image.
Same reasoning for a "Warm balance" such as that used in my humble Tungsten test above.

The D50 experiment remains inconclusive. If my "theory" is right, I should have observed more variation.
The color temperature should have been way lower than 6546 K.
I made extra sure only direct sunlight was illuminating the white card...

Any ideas?

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daicehawk

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Re: Nikon D810 Monitor Calibration -- waste of time?
« Reply #1 on: November 23, 2018, 06:11:57 am »

I do not know who decided on d50 for common white point. D50 does look yellow both on screen and as sunlight. The thing is, you cannot have only the pure sunlight, there will be diffuse blue skylight. These yellow and blue are combined and our vision adapts to the sum of the sky and sun light. You can prove it by looking at higlights that do look yellow and shades that do look blueish. If we adapted to d50 pure sunlight, the highlights would be white, and the shades very blue. In my experience, d65 is a safe sunlight white balance.
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digitaldog

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Re: Nikon D810 Monitor Calibration -- waste of time?
« Reply #2 on: November 23, 2018, 12:41:53 pm »

What "monitor" are you trying to calibrate?
CCT values define a large range of possible colors of white. Standard Illuminates don't.
http://digitaldog.net/files/22Thecolorofwhite.pdf
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Doug Gray

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Re: Nikon D810 Monitor Calibration -- waste of time?
« Reply #3 on: November 23, 2018, 07:07:59 pm »

I do not know who decided on d50 for common white point. D50 does look yellow both on screen and as sunlight. The thing is, you cannot have only the pure sunlight, there will be diffuse blue skylight. These yellow and blue are combined and our vision adapts to the sum of the sky and sun light. You can prove it by looking at higlights that do look yellow and shades that do look blueish. If we adapted to d50 pure sunlight, the highlights would be white, and the shades very blue. In my experience, d65 is a safe sunlight white balance.

Direct sunlight without light from the blue sky around the Sun has a warmer temperature than D50. IIRC it's around 4700K. The skylight that isn't direct sunlight moves the overall color temp. up to differing amounts from 5500k to 7500k or so depending on cloud cover, time, orientation, and such. D65 is considered a reasonable approximation to a mix of direct sun and blue skylight.

That said, I use D50 for my monitors.
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alecdann

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Re: Nikon D810 Monitor Calibration -- waste of time?
« Reply #4 on: November 24, 2018, 05:32:25 pm »

What "monitor" are you trying to calibrate?
CCT values define a large range of possible colors of white. Standard Illuminates don't.
http://digitaldog.net/files/22Thecolorofwhite.pdf
This is anecdotal but perhaps helpful...A friend put that question to Yoshi Ohno at NIST (current President of the CIE) and Ohno's response was that D50 was created as a reference because its spectral power distribution is fairly even across the visible spectrum.

Keep in mind that D50 doesn't exist in nature -- it's a reference used for computation. See Doug Gray's comment above.
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digitaldog

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Re: Nikon D810 Monitor Calibration -- waste of time?
« Reply #5 on: November 24, 2018, 05:41:26 pm »

The series of D-illuminants was adopted by the CIE in 1971 based on 622
measurements from the early 1960s: 249 at Rochester, NY (Kodak); 274 at
Enfield, England (Thorn Electrical Industries); and 99 at Ottawa, Canada
(National Research Council). Each of these labs contributed spectral
measurements taken with different kinds of instruments measuring at
different spectral intervals over slightly different ranges. The data
were then combined.
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GWGill

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Re: Nikon D810 Monitor Calibration -- waste of time?
« Reply #6 on: November 24, 2018, 07:07:45 pm »

Keep in mind that D50 doesn't exist in nature -- it's a reference used for computation. See Doug Gray's comment above.
I've certainly measured mid day, clear sky color temperatures of near D50 - but this is very location, time & weather/air condition dependent. Of course a standard has not been set by any one such reading, but by a combination of real world measurement and other considerations.
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Doug Gray

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Re: Nikon D810 Monitor Calibration -- waste of time?
« Reply #7 on: November 24, 2018, 10:07:47 pm »

Good, detailed article. Really large data set taken at Granada, Spain which is quite similar to most of the continental USA.  See especially Figures 2 and 5.

https://apps.dtic.mil/dtic/tr/fulltext/u2/a525941.pdf


Here's a test question: It (figure 5) shows the average CCT near sunset or sunrise when the Sun is just several solar disk diameters above the horizon is very high! Like over 9,000K. Yet people often talk about 3,000K to 4,000K that time of day.  It's obvious once you hit on it.
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