Best Scanning Options

I like to print at 300 dpi if at all possible. So you'll have to figure the largest print you might want to print and set the scan dpi for that. If it's an 8 x 10 you'll need 3000 x 2400 pixels. So for an 4 x 6 you'll want to scan at 3000/6 or about 500 dpi. Most scanners will have a standard 600 dpi setting. If you plan on a larger photo do the same math.

If you have slides to scan then you'd probably want to up the resolution to about 2400.

As far as scanning I use a Canon Canoscan 8600F scanner that can scan multiple photos at one time and put them each in a separate file. That's speeds up the scanning process considerably. I would imagine other brands of scanners would have similar features. The Canon also will scan 4 slides or a film strip and separate the images into separate files.

I'm not familiar with commercial scanning services. You can get an idea of price by Googling and see what you find. A lot depends on the amount of time you have to do the scanning. I'm retired so that's not a problem. If you have the time you might find that having them done commercially will cost several time more that the cost of a good scanner.

NOTE: If you're scanning black and white photos scan them as color because iPhoto doesn't play well with the grayscale file format.

TIP: For insurance against the iPhoto database corruption that many users have experienced I recommend making a backup copy of the Library6.iPhoto database file and keep it current. If problems crop up where iPhoto suddenly can't see any photos or thinks there are no photos in the library, replacing the working Library6.iPhoto file with the backup will often get the library back. By keeping it current I mean backup after each import and/or any serious editing or work on books, slideshows, calendars, cards, etc. That insures that if a problem pops up and you do need to replace the database file, you'll retain all those efforts. It doesn't take long to make the backup and it's good insurance.
I've created an Automator workflow application (requires Tiger), iPhoto dB File Backup, that will copy the selected Library6.iPhoto file from your iPhoto Library folder to the Pictures folder, replacing any previous version of it. It's compatible with iPhoto 08 libraries and Leopard. iPhoto does not have to be closed to run the application, just idle. You can download it at Toad's Cellar. Be sure to read the Read Me pdf file.

For a slideshow all you'd need is the pixel dimensions of the monitor or projector that you'll be using. However, for books and other printing you'd definitely want the higher resolution. For slideshows using the Ken Burns effect you would want higher resolution that a straight slideshow due to the zooming involved.

Just remember, you can always scale down but never up.

OT

the math is pretty easy - dpi is dots (or pixels in this case) per inch

DO for a 300 dpi print that is 11 inchs wide and 7.5 inches high you need 11*300 x 8.5*300 or 3300 x 2550 pixels - that is a 8.415 megapixel photo

For a screen display you need onlyenouth pixels to fill the screen (OLD VGA 14" monitors would only need 480 x 640) - look at you screen specs and you know the minimum photo size to fill it - fro printing just multiply the print size by the desired dpi and you get teh needed photo size

LN

Yes - you have the math correct

And (this is pushing my knoledge) be careful of actual scan resolution and interperlated resolution - some (maybe all for all I know) scanner advertise a very high resolution but when you read the fine print you learn that they scan at 300 dpi or 600 pdi or something then up software to upsample to 2400 or 4800 dpi - this is NOT the same as scanning at the desired resolution


LN

Check to see what the optical resolution of the scanner is. That should be what you can achieve without the interpolation that Larry mentioned.