Resolution Size Quality what do I need

Trying to decide what resolution you need can be confusing so I will try to guide you in your decision. 

Keep in mind that you can always create a lower resolution image from a higher resolution image but you can not go the other way because you just do not have the information to do it with good results.  Like wise you can make a High resolution photo look good small but it is hard to make a Low resolution image look good very large.  It is all about how much information is in the file.

The first thing you will need to do is decide how you plan to use the file.  Once you know how you want to use the file you should also decide how big the final image needs to be.  Are you trying to make a 3 x 5 inch picture on a printer or are you trying to print a 16 x 20 inch picture?  Perhaps you just want to use it as a background on your computer screen.  You should decide what you are doing with the image and then buy the image that has enough information in it to produce a good result in the final output.  You need a larger file to print a picture on your printer than you need to display it on your computer screen.  So what are the options and which option is best for each application?   Below is a list of many common uses and the "Resolution" I would recommend to get the best results for the best price. I am offering 3 standard resolutions to choose from.

Low Resolution: about 1000 x 700 pixels at 200 dip for horizontal shots or 700 x 1000 for vertical shots.  File sizes run from 1MB to 2MB in size. Common uses would be:
Screen backgrounds, screen savers,.  
3x5 and 4x6 inch prints
For use in Email, and other office applications.
Resize even smaller to use on Web Pages etc...
 

Medium Resolution: about 2700 x 1800 Pixels at 300 dpi for horizontal shots and 1800 x 2700 for vertical shots. File sizes run from 7MB to 11MB in size.  Common uses would be:
5x7 and 8x10 inch prints
Other applications where high quality but smaller images are needed.
 

High Resolution: about 5400 x 3500 Pixels at 300 dpi for horizontal shots and 3500 x 5400 for vertical shots. File sizes run from 30MB to 50MB in size.  Common uses would be:
11x14 and 16x20 inch prints
Other applications where high quality and larger images are needed.