At 09:50 AM 8/9/99 +0100, Richard Ross wrote:
[snip]
>Now here's my question: I've often seen this business of 72dpi as being the
>same as screen resolution and therefore the optimum for scans to be
>displayed on monitors. But, I can set my 15" monitor to 640x480, 800x600,
>1024x768. So the dpi is going to vary by quite a lot. While the physical
>dots per inch of a screen might well be 72, surely an image scanned at that
>resolution will not necessarily be *displayed* at that - it will depend on
>the relationship between the dpi of the screen and the video card settings.
> Won't it? Or am *I* missing something?
Richard:
No, the *physical* dpi of the screen remains constant (72 or 96dpi, or some
other figure -- you can determine it from the "dot pitch" of your monitor
specs), whereas the "displayed dpi" (for lack of a better term) can vary by
screen resolution setting. At lower resolutions, your video driver/card
simply uses more than one physical pixel to display one logical pixel. You
can check this out simply by squinting closely at your screen while
choosing differing resolutions. On high-end monitors with tight focus,
switching resolutions like this can cause undesireable moire patterns
because of the lack of a 1:1 relationship between "physical pixels" and
"logical pixels." Thus, my monitor (a Nokia 445XPro) has a moire
elimination mode which you have to fiddle with every time you switch
resolutions. Needless to say, I don't tend to switch very often (my
default is 1280 x 1024, 32bpp colour depth -- nice for working with
true-colour JPEGs etc.).
I ignore scanning resolution dpi, and just work with absolute pixel
dimensions of the image. Then it doesn't matter what dpi you use (at
least, it's never mattered for me).
Garth
"A bad day doing photography is better
than a good day doing just about
anything else."
The Unofficial Olympus Web Photo Gallery at:
http://www.taiga.ca/~gallery/
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