Focusing screen that has 5x7 or 8x10 crop markings

Is there a focusing screen or overlay of some sort that would show me the field of an 8x10 for example while I'm shooting. Sometimes I take a shot that's intended to be printed as an 8x10 and I don't have enough room to crop it.

There are third party focus screen manufacturers that do offer focus screens with grid lines. Check out Katz Eye.
http://www.katzeyeopti​cs.com …non-DSLRs--cat_canon.html

The gridded focusing screen offered by Canon for cameras like the 40D and 50D has marks (used for ensuring parallelism of vertical lines) that are conveniently placed where the crop lines for 5:4 proportion are located!

gjl711 wrote in post #10331207
There are third party focus screen manufacturers that do offer focus screens with grid lines. Check out Katz Eye.
http://www.katzeyeopti​cs.com …non-DSLRs--cat_canon.html

It is important that buyers be aware of affects of these aftermarket screens on the accuracy of the metering. Katz Eye states, for example:

"Spot Metering Mode: Our testing showed spot metering mode to be within factory tolerance for all lenses having a maximum aperture of f2.0 or larger (lower f number). Lenses having a maximum aperture smaller than f2.0 (lager f number) will show a significant shift toward increased exposure, with the shift increasing for lenses with smaller maximum apertures. Spot metering mode is not recommended when using a split prism focusing screen except with very fast prime lenses. However, if spot mode must be used, it is strongly advised to first take a test shot, check the histogram, and adjust exposure compensation as required."

Looks like the EF-D might do the trick. Thanks for the insight!