Parralax Error and Natural Lighting (the real sunshine) or Natural Lighting Products (full spectrum)
http://www.ehow.com/how_10000073_prevent-parallax-error.html
Errors in Measurement
http://en.wikipedia.org/wiki/Parallax
The lighting that I use to help with my no-line bifocals, so that I may actually get something crafted right.
These lights can be purchased at Fred Meyers, Krogers, and other retailers.
I am also a newbie/returning to a long lost hobby of mine, and no I do not always do so well with getting clean edges and a nice square layout.
Learning to be a professional is learning how to adjust for, integrate, and hide those minor errors in fabrication:)
Thanks,
nwdetectorist