Trust me, you really don't want to get into the differences between Pixels Per Inch, Dots Per Inch, and Lines Per Inch. (LPI is important for professional press printing.) I'd have to write pages and pages and bust out the diagrams and graphics for explanation. You also _really_ don't want to get into a discussion of screen resolution and 72ppi. That's even more messy. (I used to teach Photoshop and that was the part where the students would nod off.)
I'll put money down that you'll find absolutely no difference when printing the 300 ppi image and the unresampled 72 ppi image, provided you save them in a lossless format. That's because the images really are exactly the same. You're only modifying metadata about what size to print the image. -Kevin ----- Original Message ----- From: "Rick Faircloth" <[EMAIL PROTECTED]> To: "CF-Talk" <[EMAIL PROTECTED]> Sent: Thursday, September 11, 2003 11:28 AM Subject: RE: Image manipulation > I think you're right, Kevin... > > I've been inappropriately using "dpi" instead of "ppi", "pixels per inch", > when discussing image resolution. > > Also, I did have "Resample Image" checked. (Adobe Photoshop Elements 2.0) > I'll have to make more use of checking, unchecking that box... > > And yes, I was actually creating a new "resampled" file for comparison, > both onscreen and in print. > > The JPEG compression (even on highest setting) and resampling were > probably accounting for the difference in quality...I'll have to run a > screen and print test > on the original 300 ppi image and its "un-resampled" 72 ppi twin to see > what the differences to turn out to be. > > Thanks for clarifying... > > Rick > > > > -----Original Message----- > > From: Kevin Graeme [mailto:[EMAIL PROTECTED] > > Sent: Thursday, September 11, 2003 11:57 AM > > To: CF-Talk > > Subject: Re: Image manipulation > > > > > > Are you using something like Photoshop or Fireworks? In the > > Image Size box, > > there is a checkbox called "Resample Image". You probably > > have that (or > > something equivalent) checked and it's physically reducing > > the number of > > pixels in the image. That's why you're seeing that effect. > > > > When you do that, you're not _really_ changing the dpi, > > you're changing the > > total number of pixels. You're actually creating a different > > image, not the > > same image at a different dpi resolution. The software just > > provides the > > ability to edit the dpi as a shortcut to calculating the > > resize ratio. If > > you uncheck that box and change from 300 to 72, you're now actually > > preserving the image AND changing the effective dpi. > > > > The only accurate measure of an image's true size is the > > number of pixels in > > the image. Resolution (dpi/ppi) is just a measure of how > > many of those > > pixels are in a given size. If you preserve the number of pixels, the > > resolution will increase as you shrink the display/print > > size because it's > > the same number of pixels in a tighter space. Inversly, the > > resolution will > > decrease as you expand the display/print size. > > > > Understanding this relationship is integral to manipulating > > graphics between > > screen and print, but a lot of people don't really get into > > it because the > > tools generally do a good job of hiding it. But the image > > manipulation tags > > are probably going to expose it, and it's the format you'll > > need to work > > with. > > > > -Kevin > > > > ----- Original Message ----- > > From: "Rick Faircloth" <[EMAIL PROTECTED]> > > To: "CF-Talk" <[EMAIL PROTECTED]> > > Sent: Thursday, September 11, 2003 9:42 AM > > Subject: RE: Image manipulation > > > > > > > Hi, Kevin...and thanks for the reply and help... > > > > > > I'm not quite sure how this works out: > > > > > > >A 800x600 image at 72 dpi is exactly the same > > > >as a 800x600 image at 300 dpi. > > > >They both weigh in at 1.4MB > > > > > > I took a 1051 x 2098 image and at 300 dpi it's 3,067KB. > > > At 72 dpi, it's 360 x 503 and 220KB... > > > > > > That's quite a difference when the file is uploaded and displayed > > > on screen. They both can be made to fit a 320 wide area onscreen, > > > but the 72 dpi resolution image is obviously more desirable because > > > of reduced file size that's loading onto the page. > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > ~~~~~~~~| > > Archives: http://www.houseoffusion.com/lists.cfm?link=t:4 > > Subscription: http://www.houseoffusion.com/lists.cfm?link=s:4 > > Unsubscribe: > > http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=708.628.4 > > > > This list and all House of Fusion resources hosted by > > CFHosting.com. The place for dependable ColdFusion Hosting. > > http://www.cfhosting.com > > > > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Archives: http://www.houseoffusion.com/lists.cfm?link=t:4 Subscription: http://www.houseoffusion.com/lists.cfm?link=s:4 Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.4 This list and all House of Fusion resources hosted by CFHosting.com. The place for dependable ColdFusion Hosting. http://www.cfhosting.com
