Your light meter reads the entire visible spectrum plus probably a bit of infrared.

Your paper is only sensitive to blue and a bit of green, components that are only a very small portion of incandescent lighting (which I assume you are using). Your meter gives you a reading, but only a fraction of the light it reads is actually exposing the paper.

Daylight has a lot more blue and green in it, plus UV, so the portion of the light read by the meter that is exposing the paper is proportionally more. That means, for the same reading in incandescent and daylight, the daylight will give more exposure than the incandescent simply because the paper is sensitive to more of the daylight and very little of the incandescent light spectra.

You need to test for an E.I. in daylight. You may need to do the same for overcast and open shade as well, since these have even more of a blue/green component.

Best,

Doremus

www.DoremusScudder.com