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From: Chris Cox <ccox@adobe.com>
Subject: Re: [Tiff] How to convert MINISBLACK to PHOTOMETRIC_RGB
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To: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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Date: Fri, 23 Jan 2004 12:52:56 -0800
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At 2:30 PM -0600 1/23/04, Bob Friesenhahn wrote:
>On Fri, 23 Jan 2004, Chris Cox wrote:
>
>>  >
>>  >I am by no means an authority on the TIFF specification.  My interpretation
>>  >of the file in question is that a sensible application should render the
>>  >first band in greyscale and ignore the 2nd and 3rd since they are
>>  >extra samples
>>  >with no meaning attached.
>>
>>  Or load the 2nd and 3rd channels as alpha (not transparency) channels
>>  -- as Photoshop does.
>>
>>  It would be incorrect to interpret this image as RGB.
>
>How does Photoshop treat a second alpha channel?  Does it actually get
>used for anything?

Alpha channels are just alpha channels - they get loaded and the user 
can do what they want with them.
Only transparency (associated alpha) has any special meaning.

Chris
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