Have been using 750D plus 100mm macro for scanning black and white negatives. But I never mastered metering. I usually select a slide, meter with living view, then keep exposure for the rest, however sometimes I am having surprises since what the camera sees(or myself) sees as shadows are actually highlights and vice versa, any tip for setting adequately exposure?
Use the histogram and maximize the highlights on your (digital) camera.
Scanning slides or negatives doesn't necessarily mean "scanning exclusively perfectly exposed and developed pictures".
I also thought "one average picture and for the rest I can use the same parameters". There were things to learn for me.... such as different densities of the films (not the pictures), the results of simply imperfect developing/processing. A couple of slides I had to do again.