I dont know what is it about the L508, I have heard this underexposre complaint but mine does great. I think they had QC problems with this meter, as the work/does not work ratio seems to be 50/50......
I am surprised at Sekonic, I always thouhgt they were good meters. I guess I got lucky. If anything I get constant overexposure when I use filters, I had to actually take a pic of a gray card and see which one was the correct factor. Inavariably I get lower factors than the recommended ones, but with my gossen ultra spot I did not have this problem...go figure....