Also when working in bright sunlight, go with a lighter lens shade than when working indoors. When outside, your pupils are closed tight so very little light is getting in so you need a lighter shade. Inside is just opposite, eye ball is dilated so more light gets thru to the optic nerve so you need a darker lens to be comfortable.
As already mentioned, just adjust your lens shade (assuming adjustable auto dark hood) so you can see the weld and surrounding area but not so light that you squint. You should be able to see the puddle well but also see the surrounding metal as in groove of a joint so you know where to guide the rod or torch. If the shade is too dark, you could end up welding down the plate instead of where you intended.
By the way, I have never seen any use for a #13 lens, I don't even think you could see the sun with that. Even at 500 amps, a number 12 is still pretty dark. Before advent of auto dark hoods I used a number 10 gold lens by American Optical for everything indoors and it was OK for inside work, but if I move outside, I switched it out for a #9 shade.
I worked on pressure piping and vessels so any arcs struck outside the weld bevel could get you fired or at least reprimanded and the arc strike had to be ground out, dye penetrant checked for cracks and then welded up, so they didn't want those to happen. A welder had to be able to see a bit before the arc was struck therefore # 10 was plenty dark for protection and comfort.
