I got a used pentax digital spotmeter and found its reading one stop over that from canon 1v in spot mode(85/1.8 lens). Target is evenly lighted wall. Changing the lens to 50mm, 200mm doesn't affect the camera reading. My friend's eos5 in spot mode gave same data as my 1v. I also found that camera meter seems to be more sensitive. At very dim situation camera meter can still give a reading, for example, 3sec f2.8 at ISO200 but pentax meter just gave zero EV. Is this pentax meter defective?