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Author Topic: DCRaw 9.02 ProPhoto reference white point D65?  (Read 4507 times)

xpatUSA

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DCRaw 9.02 ProPhoto reference white point D65?
« on: July 13, 2012, 11:52:05 AM »

DCRaw 9.02 outputs ProPhoto with a reference white point of D65. And the output file's profile tags give 0.9642, 1, 1.08249 which are indeed so. However, most sources, such as Bruce Lindbloom, refer to ProPhoto as using D50.

I'm sure that Dave Coffin chose D65 quite deliberately. Anybody know why?

Thanks,

Ted
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best regards,

Ted

digitaldog

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Re: DCRaw 9.02 ProPhoto reference white point D65?
« Reply #1 on: July 13, 2012, 03:36:36 PM »

Only Dave could say. But I’d like to point out that if the white point isn’t D50, well then he can’t call it ProPhoto RGB. Cause that isn’t how it was spec’ed.
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Andrew Rodney
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xpatUSA

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Re: DCRaw 9.02 ProPhoto reference white point D65?
« Reply #2 on: July 13, 2012, 04:22:24 PM »

Only Dave could say. But I’d like to point out that if the white point isn’t D50, well then he can’t call it ProPhoto RGB. Cause that isn’t how it was spec’ed.

Indeed. However, I'm loath to bother Mr Coffin with it, he probably only gets a kajillion e-mails a day about his excellent brain-child. Is "ProPhoto" a registered name of some sort, to your knowledge? All I've found is Kodak's ROMM White Paper which doesn't use that name at all. Take your point though, it is a little confusing.

Ted
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Ted

sandymc

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Re: DCRaw 9.02 ProPhoto reference white point D65?
« Reply #3 on: July 13, 2012, 04:51:53 PM »

Dave's official manpage (http://www.cybercom.net/~dcoffin/dcraw/dcraw.1.html) actually calls what DCRaw produces "Kodak ProPhoto RGB D65".

Which is truth in advertising ;D

Sandy
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digitaldog

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Re: DCRaw 9.02 ProPhoto reference white point D65?
« Reply #4 on: July 13, 2012, 04:59:33 PM »

It isn’t a matter of something be registered, it is just that a color space like this is defined by primaries, gamma and white point. You wouldn’t call sRGB that name if you altered it’s white point. You could probably call it a modified sRGB which Sandy suggests is what Dave is doing here. And I’m OK with that. ProPhoto RGB D65 (with or without Kodak in the name) is truth in advertising! And it allows users to know exactly what is and isn’t modified within the spec of the color space.

As to why this was done, that would be something Dave should be able to answer.
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Andrew Rodney
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xpatUSA

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Re: DCRaw 9.02 ProPhoto reference white point D65?
« Reply #5 on: July 13, 2012, 06:21:24 PM »

Thanks Gents,

And thanks for the link to the "manpage" - I hadn't been there before. I was using the Google translation of Guillermo's spanish page - and it suffers in the translation a bit.

best,

Ted
« Last Edit: July 13, 2012, 06:28:46 PM by xpatUSA »
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