Originally Posted by
Pere Casals
All depends on the bellows extrension you add, circle grows proportional.
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If you shot very, very close sure it will cover, first your circle may even grow x2, and second... probably your corners will be well in the Out Of Focus, so probably you may use the outer illumination circle that is not considered in the image circle because it is not sharp enough, but this is irrelevant if what there is also in the OOF !
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To remove the FFD from the calculations:
With a 105mm lens, first you focus at infinite, then if you have to add 105mm to focus close, then your distance is 210mm, compared to the nominal 105 you have x2, so your image circle will also grow x2.
E= Extension (Belows)
D= Distance
F = Focal
1/F = 1/E + 1/D
If you have the distance then you have the Extension, as F is known, 105mm. If you compare the Extension to the Focal then the nominal circle grows the same proportion.
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