I have been working on a technique to produce a timelapse series of the sunset and am trying to use Aperture Priority since the lighting changes so rapidly. I am using a Canon 6d with a Rokinon 24mm lens that has no electronic connection to the Camera. While the 24mm is a fantastic landscape lens it is very soft at low focal ratios and even alittle soft at f/8, so I am using f/11. The camera is set to an ISO of 200 and of course the camera determines the exposure length in aperture priority.
All of my images are severely underexposed and admittedly I have not played around with ISO, but as I understand it, if I increased ISO, the camera would only decrease the exposure length by an equivilent number of stops to produce the same underexposed image. How can I get Aperture Priority to produce a properly exposed image with a mechanical lens like the Rokinon that is set to a modest aperture and has no electronic connection to the camera.