Best DPI for 5x7 digital file?
I am looking to sell a digital image to a client. After much research and thought, I am going to sell them a 5x7 size, and the ability to print where they would like. My only question/concern is what DPI do I save this at so they can not print larger images. I just uploaded 3 files to Shutterfly, since they tend to tell me what will/will not work. I used 300 DPI, 200 DPI and 150 DPI. It seems that a 300 DPI (sized at 5x7) has no issue printing all the way up to 20x30. The 200 DPI has no issues all the way up to 11x14, and the 150 has issues at anything over 5x7.
So it would seem that 150 would be the size, but I want to confirm with other photographers. What DPI would you recommend using? The file size just seems so small at 2.5 MB.
So my situation is that I have a client that purchased a photo, and they would like a digital file for facebook and such. I don't want to just hand over a file, 72 DPI or whatever... So I am thinking of selling them the 5x7 size for $100, but I do not want it printed larger than 5x7.
I have a Canon 50D. I always shoot highest quality. Have lots of super large images on my laptop...