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Old Jul 13, 2004, 9:28 AM   #1
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If I use the custom preset white balance feature of the D70 is it possible to tell what the Color temperature was at the time of shooting?

The Nikon Capture software allows me to change and adjust the white balance temperature, but never does show what the "recorded value" actually was.

PS/

Thanks to all those that contributed to the posting "Which parameters with D70". The settings were helpful for a new user in experimentingand the comments on your settings helped me understand the "whys".
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Old Jul 13, 2004, 10:23 AM   #2
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***
If I use the custom preset white balance feature of the D70 is it possible to tell what the Kelvin temperature was at the time of shooting?
***

Greetings,

When you say "Kelvin temperature" you are by default describing a non-uniform distribution of light intensities (non-uniform with respect to wavelength, or color.)
There is no way you can determine the Kelvin temperature from a single exposure of a uniformly reflective photographed field since each pixel measurement will be an integrated value corresponding to a single reflectiviity or brightness value in the surface you used to make the custom preset determination. What you need is a spectrum. What you are asking for is difficult to determine precisely even with a dedicated color temperature meter thanks to the complexity of the real world of light.

Hope this helps.

Richard S.
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Old Jul 13, 2004, 10:44 AM   #3
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Perhaps I was using the wrong term. In the D70 instruction manual it refers to "color temperature". This is what I was wanting to get the "temperature" of when using preset white balance. Kelvin temperature was my mistake in trying to explain what I wanted.

Thanks.


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Old Jul 13, 2004, 9:13 PM   #4
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You made no mistake. Color temperature is measured in degrees Kelvin, a unit named for the man who invented the Kelvin temperature scale.

What you are asking is a natural and interesting question. Just not easy to answer with the information the camera is measuring. I think the problem is that "white balance" and "color temperature" are really two completely different things. The camera is measuring white balance by measuring three values, the brightness of red, green, and blue, to store away and use for converting future picture values so that grays will always be gray whenever you photograph under that illumination.. It knows how to do this because you have presented it with a neutrally reflecting field for the purpose of the measurement. That is all it needs for that purpose. When you ask for the color temperature of the incident illumination that gave those three values, you are asking the camera to be a color temperature meter and that is an entirely different mission from the one the camera is designed to perform. The cameras probably could be programmed to calculate an approximate value since they have the measurement values and know the dominant wavelengths of the three color filters used in teh pixels, but I know of no camera that currently supplies that information.

Hope this helps.

Richard S.
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