It is important to understand the concept of DPI and PPI in the preparation of your project to digitize images. You need to choose the best option for your project will do. PPI, or pixels per inch, referring to the number of pixels in your digital images contain. This will affect the size of your photo prints, and quality production. For archival purposes, you want to be like a large PPI can be for the image containing the original information as possible. If the pixels per inch is too low, the image pixels should look like billboards that look jagged and unpleasant. Notice in the pictures below for a quick visual on how PPI could affect the quality of the output image.
There are no concrete figures for the PPI you need to print images, however, with an impression that you can go with the PPI is much lower because you see large prints from a distance over a small section, you can go with less PPI and still have a good view images.
DPI refers generally to the printer. Each pixel is composed of different colors that the printer must mix and match accordingly. Each pixel consists of small dots, the more dpi, the more points are there to fill in pixels, which gives better color mixing and tone of the image. With more PGD must also end up with more ink and more time printing a picture of each. At least IPR would produce less ink dots per pixel, which makes printing more worse than PGD.
For film scanning like scanning 35 mm slide and negative scanning APS, because the original film is very small, you want to scan at the highest possible PPIs to maintain the original data. Remember you can always resize your image to a moment later, and you want to change the size of high quality scans you can use the web.