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Field of view of a lens? Answered

Hunting through the attic I found an old 35mm projector.

I wondered what governs the field of view of the lens system - for this projector it is obviously about the size of a 35 mm slide but for my video projector it must be considerable bigger although the lens looks similar. (I know hat isn't a very scientific judgement!)



FOV is controlled by the F number of the whole , which is essentially the ratio of diameter of the first optic to the focal length of the thing, and the size of the object to be imaged/projected. Whilst I hate to say it, the wikipedia article

is, to coin a phrase, illuminating,.,...

Thanks after I posted the question I turned that up. Interesting.

However it isn't helpful to turn the projector lens and an old small monitor I have into a video projector. Have to think further.