After some experimenting, I want to share how I have successfully enlarged one of my parents' proofs, with step-by-step instructions!
1. Find the photo you want to enlarge. We decided to concentrate on wedding parties, as opposed to just photos of the bride and groom, so that guests would have the chance to recognize more relatives, but this decision is up to you. Take note of the dimensions of the print you have.
2. Find a scanner that can accommodate high-resolution scans. I did some research, and in order to get a good quality photo, you want 300 dots per inch (dpi). So if you're enlarging a 4x6 to an 8x10, you need to scan the 4x6 photo at a higher resolution than 300 dpi.
You can use a personal scanner if you have one at home. HP All-in-One Printers, along with the HP Solution Center program, allow you to scan at very high resolution, but I noticed some problems with the image that got scanned in. Probably due to imperfections in the glass on the scanner, I ended up with lines running through the digital image, like there was sunlight streaming down in odd places.
I have found the UPS Store to be a great resource in this regard. They'll do the scanning for you--it's $2 per scan--and put the files on a flash drive for you. Their highest resolution for scanning was 600 dpi, which turned out very well when I enlarged the print.
3. Organize your photos, put them on a jump drive, and head to your nearest photo printing center! My parents' 6x6 proof, scanned in at 600 dpi at the UPS Store, looks great when enlarged and cropped to an 8x10.
