I've just been comparing the auto-exposure readings from my Canon 518 Auto Zoom to those taken with a Sekonic L-308B light meter set to 100 ASA and 18fps. Camera was loaded with Ektachrome 100D, so no filter engaged, and set to 18fps.
In all the lighting conditions in which I tested and compared results, the camera's internal meter (set to auto) showed an aperture two full stops less than the external meter. So: if external meter read f/2, camera would say f/4.
I understand that reversal stock has very little latitude for over/under exposure, so these results seem to suggest that using an external meter with this camera is not a good idea, as the film will be highly over-exposed.
I wondered if anyone more technically savvy than me might be able to suggest a reason for this huge difference?
I have to say that when I have exposed reversal stock in this camera on auto-exposure the results have been pretty spot on, but the difference between the two readings is very puzzling indeed!
I wonder what Martin Baumgarten might have to say..?
All replies welcome - thanks for reading.