Yes, you can without becoming a full-time professional by selling your photos through internet. Once you started selling your photos, possibly you can become a professional. If you are already a professional doing wedding or event photography, you can easily sell some of your work online.
You have different possibilities online to sell your photos. Today, stock photography or imagery that can be licensed for specific uses is the biggest market. Besides this option, there are several possibilities open to you. You can take the help of micro stock photography sites such as Shutterstock, Fotolia, Dreamstime, Bigstockphoto, 123RF.com, Istockphoto and many other sites.
To be successful on stock photography sites, your shots should be good 'stock photographs' in high resolution format. Stock photographs are very popular with designers, graphic artist, art directors, ad agencies, marketing professionals, brochures etc.
Good quality art pictures framed professionally make good impression. Such pictures you see in restaurants and other public places. Your photo can get to that position. For this there are online agencies that can take care of all the logistics like charging the customer, printing picture from digital file, matting (framing), and sending it to the client.
To sell your photos you must know what the customers want. You should also know what style and content will sell. Then you have to advertize yourself, meaning you must be an active member of the online community, be active blogger.
You can open a free account with online sites like RedBubble, an artistic community place with commercial possibilities, and upload any number of pictures and sell as many as you want.
How to upload your photos? There are three ways. The most common one is using the web upload from which is available on all stock photo agencies. Then you have the ActiveX/Java uploading system which is available only on some of the agencies. The last one is via FTP (File Transfer Protocol) software.
