You sayf/1 is a 1:1 light ratio.
but you admit it yourself when you say:Er, no.
If a camera, with the lens set to F/1, has the same brightness at the film plane as at the subject, then the opposite must also be true. If you set your light meter to f/1, and metered the baseboard image thrown by the enlarger (using a grey card for a reflective meter), then the time given by the meter should be correct. You just measured the brightness of the subject, and at f/1, according to you, the film "sees" the same brightness as the subject. Am I wrong?At f1 the film 'sees' an illuminated solid angle of 53 degrees that is the same brightness as the subject