Having your camera on vivid and shooting Raw does not effect your image size. I do not have the ability to change the aspect ratio on my camera, but if you do and want an 8x10, you need to shoot 5:4. Also, if you are proficient at Photoshop, you can extend the background if needed to give more headroom and "save" some of those photos you lost room on when cropping.

I agree....just make sure to give enough room around the subject so cropping to 8x10 doesn't cut off anything. If you fill the frame perfectly, you will certainly loose some of the image when you crop. I shoot a couple of each photo...one filling the frame and then opening up some, so when my clients order different sizes I have something that will work.

Always unless wanting a flare is my answer as well, but something I'd add as noone brought it up....make sure you attach it correctly as if it isn't in the correct position, you could wind up with dark "edges" in your photographs. Happy shooting!

Ditto...show us some photos so we can see what's going on. Positioning of your lighting is key no matter what equipment you have.