I have a question on camera cropping. I would like to know that with a 40D if you are taking a full frame picture of a group say about 29 young ladies would you not fill the frame if you are tring to make a nomal print say 8X10 do to the crop factor.
The reason for this is do to I took that picture and I filled the frame and now if I try to crop down to a 8X10 in PS I cut off the girls. So I am thinking that by not filling the frame I will be able to crop to the smaller size needed.
The 40D has a 3:2 (width:height) image ratio. If you extrapolate that to an 8 inch height (assuming you take the group pic in landscape orientation), that would produce a width of 12 inches. Since you want a width of 10 inches - not 12, you should leave a gap of about 8% of the width of the viewfinder/LCD on each side of the frame (16% total, 2 extra inches divided by 12 total).
Since the LCD display on the back of the 40D is about 2.5 inches wide, you could put a piece of tape approx. 0.2 inches wide (2.5 * 0.08) on each side of the display and that would mask off a pretty good approximation of the 10x8 format.
I may have made a math error there somewhere but at least I ran you through the process. If you are a visual person and are using some kind of photo editing package like Photoshop, it might be easier to apply a 10x8 crop to en existing image to give you a feel for the margin you need to leave on the sides.
