Originally posted by ismaelg Correct?
Excellent!
Except... DECREASE APERTURE is ambiguous. Because aperture numbering is inverted, DECREASE is unclear: a smaller fraction, or a smaller numerator? That's why we usually say STOP DOWN or OPEN UP when we talk about aperture adjustments. And the counterbalancing forces work like this: Increasing the FL
or widening the aperture will thin-out the DOF; decreasing the FL
or narrowing the aperture will thicken the DOF.
INCREASE FOCAL LENGTH <==< DOF >==> NARROW APERTURE
and
DECREASE FOCAL LENGTH >==> DOF <==< WIDEN APERTURE
It's easier to see than to explain. Ay yi yi.