WOW! That's what I am talking about. Thanks for the chart. The cheap lamp I"m getting for $25 is 1.25X. If the lamp is too poorly built I'll just chuck it out and spend whatever I need to for a quality lamp. My eyes, neck and back will thank me. Also if 1.25 is not adequate I'll buy a #3 1.75X. The 13" focal length seems just right. Thanks everyone for your input. I"m going to put the 5 diopter lamp on my micro machining bench.