Light is light, it does not matter if its being reflected onto onto your optical sensors, a camera's electronic sensor or chemical based sensor, nor does it matter what size the sensor is.
To use a camera with a built in light meter to meter a scene for use on a different camera the built in meter camera must have a normal focal length lens, not a zoom or telephoto.
Lens used in large format, 2x3 and up, the lens will focus from infinity to the lens closest focusing distance in approximately 1/3 of the lens focal length from its infinity position. Beyond that the lens will require a double or triple the distance from the close distance to focus to the next closest foot from the film plane. 1/3 of the lens focal length when applied to bellows extension formulas equals less than 1/3 stop of additional exposure from infinity position.
Using post 6 statement of 210mm being normal for 5x7 210/3=70mm. Lets say, for the sake of argument, the lens focuses 10 feet at 65mm extension from infinity but will not focus 9 1/2 feet until 95mm from infinity then 10 feet will be considered the lens close focus distance.
An exposure error of 1/3 stop or less will not be noticeable for all practical purposes including making high end gallery/fine art prints.