White space on a print

With the other discussion here about how to mount prints I was wondering what are the conventions for how much white space to leave on a print? I'm not interested in canvas wraps and borderless prints, just prints with a white border. Is it some proportion of the total image size or a standard 1" all around? What about some prints I've seen with more white space at the bottom than the top--an off center type position? This often has a title for the print in the extra space. Also how many create their own borders in photoshop and include them on the print instead of, or in addition to a mat? Thanks--Larry

I just like a little space to help positioning in the mat and I like the mat opening cut about 1/8" smaller than the print size. I find 1/2" extra on the paper is enough.

Mel--thanks. I did some searching around on framing supply sites and found that many of the precut mats have an opening about 1/2" smaller than the photo dimensions so that means about 1/4" white space on each side to allow for just that overlap. Some folks talk about signing their prints in the wite space between the image and the mat so that also gives you some idea that you need about 1/2" for the signature there. Maybe someone will chime in with ideas on what to do if you choose not to use a mat for the print. Maybe most of the folks on here just tape their print to the wall and don't worry about mats and white space--Larry