DP2s Color Accuracy revised

Started 5 months ago | Discussions thread
xpatUSA
OP xpatUSA Forum Pro • Posts: 19,895
Re: DP2s Color Accuracy revised

wood_gnome wrote:

Still no gaps, though.

Okay, if a gap means "totally zero" You are right of course!

I seems You and me are using the word "continous" differently. To be more precise, maybe I wanted to say that so called "white" LED's do not emit like a

black-body-radiator.

(Our sun (despite some small absorption lines) and our wellknown classic light bulbs are all black-body radiators.)

I know that.

Regarding Your measurement of the LED-spectrum: A typical spectrum for modern "warm white LED". There is such a high and small spike around 450nm (from the internal blueish LED), followed by such a deep plunge in the spectrum around 480nm, then rising again to the broader plateau in the green / yellow / yellowish red (from the conversion of the LEDs internal flourescent substance), and then there is the steep fall off in the deep reds and NIR but still in a zone where human eyes can see. All in all I would not call this "continuous".

I disagree with the exaggerated terminology which applies "spin" to your rebuttal. From the valley to the orange peak the grayscale change is well under 1EV - hardly noticeable in normal scenery.

Such light might look adequate enough for human eyes. (I have changed all the bulbs to warmwhite LED in my flat). There is also the possibilty, that films and cameras at first glance output acceptable results under such lighting. But afaik there is no camera designed for such a kind of quite limited light yet. Maybe we will see a "warm white LED" WB setting on some cameras in the future? But even a special LUT calculated to counteract the distorted LED light spectrum still cannot compensate for the deep hole (no gap though ) in the "warm" blue/cyan, and the enormous lack of deepest reds in the lighting.

So what I want to say is: Be careful when combining LED lighting and photography.

Obviously good advice for general lighting advice in photography.

That lighting works well enough for my purpose which is mostly comparison between my cameras using only 6 of the Macbeth color patches and bearing in mind the reflectance spectra of those patches.

'Bye for now ...

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Pedantry is hard work, but someone's gotta do it ...

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