Quote Originally Posted by shimoda View Post
What if you are using a 35mm camera with a zoom lens for metering. Is it not so that the bellows factor is "factored" in when using an SLR reading? A zoom lense has variable max f-stop from min to max. So if I use a zoom lens to get about the same size as on the ground glass, will the metered value be usable on the folding camera?
Or am I as per usual completely off?


That the field of view is the same, doesn't mean that the bellows factor is taken into account. The lens designs are very different, at least if we are comparing typical 35mm lenses to LF lenses, so lens-to-film distance is very different, and falloff can be very different too. There are Scheimpflug issues, differences in lens coatings and contrast etc. etc.

In the limit of infinity focus, yes, you can get a good idea from 35mm metering, but for anything involving substantial bellows factor or movements etc.... usually not wise.

If you are using a 35mm camera to meter, it's best to take that meter reading and then apply the bellows factor to that reading. I do this quite often for landscapes... again, for situations with large bellows factor, beware! The 35mm cameras have the advantage of spot as well as area and average and matrix metering, which all have their plusses and minuses. Plus, if you use a digicam to meter, you can also get colour temp and scene brightness range (a histogram) and a "proof" image too.