Depends very much on the fine detail in the original. A white wall has no detail to lose, a closeup of a hairy, colorful insect has a lot. Also subtle color and tonal transitions will be lost long before actual image detail. Hard to see on a monitor, easier on a good print.
Don > -----Original Message----- > From: Jens Bladt [mailto:[EMAIL PROTECTED] > Sent: Saturday, November 13, 2004 7:52 AM > To: [EMAIL PROTECTED] > Subject: RE: Reducing File Size with Photoshop > > > I) just did some screen tests compressing jpeg's (from tiff). Until I > compress to more than 6 (12 is min compression, 0 is max, I can't > really se > any difference on the computer screen! Prints may be different, though. > > Jens Bladt > mailto:[EMAIL PROTECTED] > http://hjem.get2net.dk/bladt > > > -----Oprindelig meddelelse----- > Fra: Sam Jost [mailto:[EMAIL PROTECTED] > Sendt: 13. november 2004 14:03 > Til: [EMAIL PROTECTED] > Emne: Re: Reducing File Size with Photoshop > > > Yep, 3 for three bytes of color data for each pixel. I usually caculate in > bytes, not bits. :) > > In the ancient times before jpeg every image was uncompressed and huge. In > these ancient times hard discs had been much smaller and storage was > expensive, so a bunch of smart people sat together and invented a storage > format for images to get them a lot smaller without loosing too much image > details -> jpeg > For more information I'd suggest a look at theyr homepage > http://www.jpeg.org/jpeg/index.html > > Sam > > ----- Original Message ----- > From: "Jens Bladt" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Saturday, November 13, 2004 12:52 PM > Subject: RE: Reducing File Size with Photoshop > > > > Noooo... > > It's 6 040 064 pixel * 24 (colour depth - in bits per pixel) = > 144 961 536 > > bits = 144 961 536/8 = 18 120 192 bytes = > > 18.12 MB. > > > > I you meant 24 bits/8bits pr byte = 3 (explaining the "3" in > your math) - > > it's fine. > > > > I guess I don't understand what a jpeg compression really does! > > But you are right - I saved a jpeg file as a tif and then it > kept the 18MB > > size, showing this in the Path Finder. > > Jens Bladt > > > > mailto:[EMAIL PROTECTED] > > http://hjem.get2net.dk/bladt > > > > > > -----Oprindelig meddelelse----- > > Fra: Sam Jost [mailto:[EMAIL PROTECTED] > > Sendt: 13. november 2004 12:10 > > Til: [EMAIL PROTECTED] > > Emne: Re: Reducing File Size with Photoshop > > > > > >> Can anyone explain: > >> Why is the file size of an *ist D image say 3.936 MB in the > Path Finder, > >> and > >> 17,3 MB when opened in PS? > > > > I'd guess 3.936MB is the file size, probably jpeg (compressed) > > And 17.3 MB is the uncompressed image data for the image (3008x2008x3) > > > > Sam > > > > > > >
