Photo Booth Cropping Image

Lee Keller wrote: ... Photos taken in Photo Booth are 1280x853...

Normal behavior. Same happening here.

Lee Keller wrote: .. I wanted to know why ...

I couldn't find an Apple explanation of why, but my guess is that it must be how the software is written in conjunction with your iSight's native (maximum) resolution. (As in-built camera resolution and Mac OS X software and apps have changed over time, Apple has changed the built-in camera's name on newer Macs from "iSight" to "FaceTime" and then to "FaceTime HD." Each of these cameras may behave slightly differently in some applications.)

Lee Keller wrote: ... if it is possible to stop it....

I don't know any way.

If you like, you can send suggestions about this directly to Apple via Apple - Mac OS X - Feedback for their consideration in future Photo Booth product development.

Part of the reason is wherever the raw images come from as in a camera that is the default size the camera produces. So when you transfer or download the images that is the size they will transfer. Many users do not like to work with that large of an image and prefer to bring the images into a Photo Editing software such as Photo Shop from Adobe, or the Free Gimp Open Source Software and resize them down to a workable size to send in an e-mail or to store. This makes the file size much smaller You just have to remember to SAVE or SAVE AS to keep them and transfer them to another folder that has the re-sized images into.

You only leave the Raw image size when you need to work on the images to repair them. Hope this helped you to understand how it works.