What I usually do when I'm just out and about with the Bessa L/15 Heliar combo is meter off the palm of my hand. I'll make several readings, tilting my hand this way and that so I'm measuring both the shadow side and the brightly lit side, then I make a judgement call based on those readings. Living in South Florida and being outdoors a lot my skin, even the palms, is darker than a lot of you northerners are likely to have. You really have to do your own trials and see what works best for you.