Newbie question on image resolution

[Richard Pini]

Hello all

I've never used Powerpoint before, and suddenly need to put together a
presentation in very little time. I'm learning the basics of what I
need to do, from the little pdf manual that came with the installation.
However, nowhere have I been able to find information on how best to
scan images (since this will be mostly images, not text) for a
projected presentation (like an old-fashioned slide show in an
auditorium for a large audience).

I'm guessing that the higher the resolution of the scan, the better -
although then it would seem that each image file would be larger and
thus slower to load/project. Some image files that I have only exist as
jpegs at 72 dpi - I could up the dpi in Photoshop but that doesn't add
detail, so that seems useless.

Please, can anyone give a few words of wisdow here, or point me to a
source of information? (The Microsoft site doesn't seem to have
anything useful in this regard, and a Google search didn't help
either.)

Thanks much in advance -

Richard Pini

--

 

[Steve Rindsberg]

I'm guessing that the higher the resolution of the scan, the better -

although then it would seem that each image file would be larger and
thus slower to load/project.

Exactly so. Figure out the resolution you'll run the computer at (usually
limited by the projector, and usually 1024 x 768). Scan your images to that
or, better, scan at 2-3 times that resolution, then downsample to the final
1024x768 size.

Some image files that I have only exist as
jpegs at 72 dpi - I could up the dpi in Photoshop but that doesn't add
detail, so that seems useless.

They're not 72dpi. Photoshop just says that when it doesn't know better.
Ignore it.
DPI is irrelevant in this situation. Think pixels. Be happy. Project
beauty.

 

[Don Althaus]

I would echo what Steve said, but offer a word of caution- don't exceed the
optical resolution of the scanner if you are using a flatbed. Between the
software interpolation of the image and the Nyquist effect (data fold-back)
when exceeding the hardware frequency limit, you can actually soften the
original scan and no amount of post production manipulation can correct
that.

 

[Steve Rindsberg]

I would echo what Steve said, but offer a word of caution- don't exceed
the

optical resolution of the scanner if you are using a flatbed. Between the
software interpolation of the image and the Nyquist effect (data fold-back)
when exceeding the hardware frequency limit, you can actually soften the
original scan and no amount of post production manipulation can correct
that.

I hadn't considered that, Don. Good point. With normal size originals, it
shouldn't be an issue, but if you're scanning little fellas, it could become
one.

I haven't heard of the Nyquist effect - could you explain that a bit more?
Thanks.

 

[Adam Crowley]

I haven't heard of the Nyquist effect - could you explain that a bit more?
Thanks.

Add me to the queue of the Nyquist-deficient...

 

[Steve Rindsberg]

I haven't heard of the Nyquist effect - could you explain that a bit
more?

Add me to the queue of the Nyquist-deficient...

This is missing more than half its marbles, but those that are there will
help:

http://www.opus1.com/~violist/help/nyquist.html

Google came up with some others that are way over my head (anything that you
can't do the equations for in Notepad is way over my head, though, so don't
let that scare you off).