Mailing Lists: Apple Mailing Lists
Image of Mac OS face in stamp
Re: Luminosity channel...
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Luminosity channel...

Yesterday Carl Stawicki asked:
>Does anyone know how PhotoShop calculates the luminosity channel?

To which I replied:
> Photoshop used to do it like this:
> Luminosity = 0.299 * R + 0.587 * G + 0.114 * B
> but I don't know if this method has been replaced by one that uses profiles.
> I could find out, if you really want to know.

I looked into it further today with PS 6.0.1 and it appears as though the
above equation (which are the NTSC weightings, BTW) is still used when PS
calculates the "Luminosity" histogram of an RGB image. I don't think
profiles or RGB working spaces have anything to do with it at all.

I haven't a clue how the Luminosity histogram is calculated for a CMYK
Bruce J. Lindbloom, Pictographics Intl. Corp.

Visit the Apple Store online or at retail locations.

Contact Apple | Terms of Use | Privacy Policy

Copyright © 2011 Apple Inc. All rights reserved.