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.
>
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