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From: Andrey Kiselev <dron@ak4719.spb.edu>
Date: Sun, 9 Dec 2007 21:39:57 +0300
To: tiff@lists.maptools.org
Subject: Re: [Tiff] dpi settings
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Status: RO

On Sun, Dec 09, 2007 at 11:15:51AM -0600, Bob Friesenhahn wrote:
> >For me centimeter unit is quite inconvenient for the image processing
> >related usage. I like mm.
> 
> It seems that the best unit to use depends on what is being measured
> and the intent of the measurement.

That is very true. And we are talking here about resolution tags which
intended to set up the relation between image pixels and actual size of
paper sheet or display. And millimeters are quite convinent in measuring
of paper sheets and displays.

> For example, if the TIFF file represents a satellite image covering a
> large expanse of the earth, and it is desired to specify the actual
> resolution, units of millimeters would be inconvenient.  Perhaps
> meters or kilometers would be more convenient.  If an image is from a
> microscope, perhaps nanometers or micrometers would be more
> convienient.

Oh, no, you are just mesunderstanding the resulution tags purpose. They
have nothing to do with the actual image content. The same 300 dpi image
can be the view of the whole Earth from space or just a bacteria
photograph, but it still remains the 300 dpi image. The scale of the
image content should be established via anther tags.

Best regards,
Andrey

-- 
Andrey V. Kiselev
ICQ# 26871517
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