Try this formula: (New focal length/Old focal length) X Old image circle = New image circle. Do check the mathematics to see if the approximation is good enough for you. What would suggest for a more exact calculation?
"New focal length" in the above formula is the result of adding a supplementary lens (positive or negative dioptre) to the original "Old focal length " lens.
Photography:first utterance. Sir John Herschel, 14 March 1839 at the Royal Society. "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..".
Too late to edit. Mental lapse. My beastlets (see post # 31 above) are Comparons, not Componons. Oops!
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