8x10 exposure size?

I'm sure this has been asked, but I cannot seem to find it using the forum search tool, or using google to search the site. What is the actual exposed film size (presumably set by the window size in the film holder). I've seen this page: http://home.earthlink.net/~eahoo/page8/filmhold.html but it lists the long dimension as being greater than 10" which does not seem correct. I've also seen 9 5/8 (9.625") suggested. I am trying to figure out what size the inner dimension of a bellows frame needs to be. The bellows builder (china) recommended 9.85" as the ID of the bellows frame which sees pretty small to me, but maybe is fine.

thanks!

You want to use 10 inches as the min 10.25 inches is bette. the closer the size is to the film image size the more likely you will vignette the image when using movements

The citation in post #1 is in error. This has frequently been discussed on this forum and elsewhere, most recently at http://www.largeformatphotography.in...lder-seems-odd. For the complete dimensions of film holders scroll down to post 20 in this citation. The window as specified by ANSI is a minimum of 9.575 x 7.667 inches.

UJMMM . . . . .Why not expose a sheet, process it then directly measure the exposed potion? It will be wider on the end with the loading flap and narrower where the raikls hold the film flat.

A follow-up question: Why does the exact measurement as opposed to the nominal dimension matter?