@TCampbell wrote:
Something to keep in mind is how the metering system works.
If you have a hand-held light meter, the light is falling directly on the meter. There is no lens. The meter reports the amount of light.
If you have a meter in a camera, then light has to pass through the lens before it reaches the meter. Since an f/4 lens reduces the light more than an f/2.8 lens... the meter doesn't really know how much light is actually in the environment unless it also knows how much the light is reduced as it passes through the lens.
For electronic lenses that interface with the camera, that information is reported and the camera can properly calculate the exposure. But for a completely manual lens with no electronic interface, the camera has no information about the lens, doesn't know the lens aperture, and can't realistically make any prediction about any exposure (not an accurate exposure anyway).
There are some manual lenses that are "chipped". Rokinon makes lots of lenses that are comletely manual, and often they make the same version in an edition that talks to the camera. If you use a completely manual (no communication of any kind) lens, then you would need to meter with an external light meter to get an accurate meter reading. If you have the chipped version (electronic interface) then it's still a manual lens, but at least the camera knows what's attached and the f-stop ... so it can provide a meter reading which is likely to be accurate.
Not quit following this argument. It would make sense if the exposure is made at maximum aperture, and the lens stops down when you take a shot. But, the aperture does not change with a fully manual lens. IMHO, what you meter, is what you get.
I use Auto ISO so that I can adjust shutter speed, or aperture, and still get the proper exposure.
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