# Re: Calculating Scan Size

From: Jon Danforth ^lt;jdanforth@sc.rr.com>
Date: 02/20/04-01:40:21 PM Z
Message-id: <002101c3f7e9\$610d0630\$6401a8c0@Hualon>

Good point. I always scan into an uncompressed 16 bit TIFF so I didn't even
think about getting into compression. Mike's right because there really is
no easy way to calculate size on disk.

Those calculations are handy when you get in a digital vs. analog argument
and someone brings up megapixels as their only arguing point. My response?
Well if you're only counting megapixels then I've got way more on a 645
negative than you do.

:p

-Jon
----- Original Message -----
From: "Mike Finley" <ekng532@f2s.com>
Sent: Friday, February 20, 2004 2:26 PM
Subject: Re: Calculating Scan Size

> On Fri, 20 Feb 2004 14:11:43 -0500, Jon Danforth <jdanforth@sc.rr.com>
> wrote:
>
> >Sandy,
> >
> >Try using the scan calculator at scantips.com. I use this all the time.
> >
> >http://www.scantips.com/calc.html
> >
> >For instance, scanning a 645 negative at 2400dpi yields these results:
> >
> >Input
> >(2.205 inches x 2400 dpi) x (1.693 inches x 2400 dpi) = 5291 x 4063
pixels
> >Output
> >(10.419 inches x 508 dpi) x (8.000 inches x 508 dpi) = 5291 x 4063 pixels
> >
> >This also gives you the equation for calculating it on your own later on.
> >To get the size in MB, you'll have to then multiply each value by the
number
> >of bits per channel (8 or 16) by the number of channels. Then you divide
> >multiply the number of bits by 8 to get the number of bytes and then
divide
> >that number by 1024 to get the number of megabytes.
> >
> >So if you have a grayscale image, that's 5291 * 8 = 42328 + 4063 * 8 =
32504
> >= 74832 bytes / 1024 = 73.08 MB.
> >
> >RGB color is just three times that (roughly). Keep in mind that these
> >calculations are based on scanning at 2400dpi.
> >
> >There's probably a more simple way of doing it but I'm a bit rushed right
> >now. The light outside is AWESOME.
> >
> >-Jon
> >
>
> This gives the megabytes of image data in the file, but doesn't
> necessarily equate to the file size on the disk, if that was what
> Some formats compress heavily, and throw away data in the process, eg
> JPEG
> Some formats compress less heavily and can restore exactly the same
> data when opening the file.
> Some formats do not compress at all.
> Tiff files can be any of the above, depending on options chosen
>
> In addition to the image data there will be a small amount of
> additional data needed to identify the contents to software that is
> using it.
>
> So if you are talking about file sizes on disk, then there is no
> direct correlation to resolution and image size.
>
> mike
>
>
> mike
> Mike Finley, http://www.efikim.co.uk
Received on Fri Feb 20 13:40:50 2004

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