I actually do have some experience working with aluminum. Here's a question. I see the goal is to have an opening larger than the frame size so that some exposure takes place through the clear part around the image. Some "filed out carrier" images have what is clearly an exposure through this clear part, then the outside edge of this black border is somewhat soft - not a hard edge I would expect from cut of aluminum. How is THIS done? Just a random reflection and diffraction from jagged edges?
How come mat board isn't an approximate?? (not in term of honing skills but visual impact)