Re: Calculating Scan Size

My purpose in asking the question has nothing to do with arguing
point. I am making some scans of large 5X7 negatives and want to keep
total file size below 700mb so I can save the raw file to a CD.
Unfortunately the scanning software that I am using does not tell me
the final file size after I indicate resolution and target size, as
some software does.

Sandy

>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>
>To: <alt-photo-process-l@skyway.usask.ca>
>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
>> Sandy was asking about.
>> 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 14:44:22 2004