I have a Gossen Luna Pro F I use with my Toyo 4x5. Before I got the Luna Pro, I used my F80 as a light meter, with reasonable results. The Luna Pro reads consistently one stop under the Nikons, and as a result the pictures are generally underexposed. To remedy this, I set the light meter at half the box speed, which has worked out ok. I recently bought a RB67, and ordered a Gossen digisix meter for it, which arrived today. The digisix reads within a hair of the Luna Pro. I don't understand why there would be a whole stop difference between the Nikons (all of them, generally irrespective of centre-weighted or matrix) and the Gossens. It's nothing I can't work around, but I'm curious as to why the difference. Perhaps "curious" is not a strong enough word. It bugs the hell out of me.