Re: Calculating Scan Size

Photoshop needs a lot of RAM and Scratch disk space.
A G5 Macintosh can have 4GB or 8GB of RAM depending
on the model.

Photoshop used to have a size limitation of 30,000
pixels in either dimension and a total file size limit of 2GB.

Photoshop CS supports 300,000 pixels in either dimension.
There is a 4GB limitation on saving Tiffs, so if you're making
larger images than 4GB you can save in Photoshop RAW or use the
new Photoshop native format (PSB) "Large Document Format".
Both formats support unlimited size.
You will not be able to open these files in Photoshop 7 or earlier
versions.

Also, Photoshop will address a maximum of 2GB of RAM.
So if you are working with larger images, Photoshop will need
a lot of free Scratch disk space. That's the point where hard
disks spinning at 15K RPM show their worth..

-Phillip

Sandy King wrote:

> Eric,
>
> I am just curious how you are able to work on files that are too
> large to fit on a CD? It takes my Mac G4 forever to make changes in
> Photoshop on anything larger than 700mb-800mb.
>
> Sandy
>
> >Sandy, Perhaps it is time for a DVD burner and move up the scale. ; )
> >I had a couple of frustrations with files just a bit too bit for a cd.
> >
> >
> >Eric Neilsen Photography
> >4101 Commerce Street
> >Suite 9
> >Dallas, TX 75226
> >http://e.neilsen.home.att.net
> >http://ericneilsenphotography.com
> >
> >
> >> -----Original Message-----
> >> From: Sandy King [mailto:sanking@clemson.edu]
> >> Sent: Friday, February 20, 2004 2:41 PM
> >> To: alt-photo-process-l@sask.usask.ca
> >> Subject: 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 Sat Feb 21 14:38:53 2004