It is most important that you make sure you have the right size and resolution for your projects. For the Old Photograph Digital Retouching Project, you are required to use a resolution of 200 ppi, with a size of about 5 x 7 (or 7 x 5). 5 inches x 200 ppi means that you'll need a minimum of 1000 pixels in either width or height. If your original photo is smaller than that, make sure to scan it at a higher resolution (a 400 ppi scan would allow you to double the size of your photo, 600 ppi would allow you to triple the size). There is a scanner in the Library/Info Hub and the techs there can help you make the scan if need be.

To adjust size/resolution in Photoshop:

1. Choose IMAGE > IMAGE SIZE
2. Uncheck RESAMPLE IMAGE, so as not to artificially and accidentally enlarge or reduce the number of pixels you have in your image.
3. Set the RESOLUTION to 200 pixels/inch.
4. Check the width/height in inches of the document size. If it is smaller than 5 inches in any one dimension, you'll need to rescan your document (as it is too small). If it is larger 5 x 7, you can now throw away some pixels as you know you don't need them since you've already set the resolution to 200 ppi (the required print resolution).
5. To reduce the size, check RESAMPLE IMAGE and reset the height or width (with CONSTRAIN PROPORTIONS checked). It's likely that your image may not be exactly 5 x 7 and that's okay, provided no dimension is smaller than 5 inches. You can use IMAGE > CANVAS SIZE to further crop/reduce the size if for example you had a width of 5 inches and a height of 8 inches and wanted to crop some of the height.