The D70 program is designed in order to not blow the highlights. This could be the problem. When the camera thinks instead of you and you dont know how the camera thinks... but you can measure the light in differet little zones (using the logest focal length of the lens ) and deduce the correct f and t. Don't let the camera choose between a range of different amount light. Or you could buy a hand meter at ebay, I bought a Sekonic L-248 for 10 $ shipping included (from california to europe) and I think it's a great meter ( and much less heavy than your metered camera).