In article <01bba372$ea64e2a0$2cdca4cd@tmilano>, tmilano@monmouth.com says...

>Forgive me for the dumb question but I'm new to photography. What is 1 to
>1?

1:1 is the ratio of film image of the subject to the subject size, when both
are the same, as in "life size image on film" (1:4 would be, for example,
when the subject is rendered 1/4 life-size on film; or 2:1 would be the
description of a 2x magnification of the subject size on film).
Hope This Helps