Originally posted by D1N0 I got you started already It's called equivalence for a reason. It is not about the F number it is about similarity in the actual image.
Absolutely wrong. Equivalence is only about the field of view. Only FF promoters claim it's about depth of field.
The simple fact is, ƒ2.8 on a 100mm lens on APS-lens will have the same field of view and use the same exposure value as ƒ/150 2.8 on FF. Two variables are used and are addressed in equivalence formula. As far as I know, there is no formula that determines equivalent depth of field. Maybe you can point us to one if you think it's a thing. But as far as I know, DoF is not adressed as a variable in any equivalence formula. A DoF equivalence would have to be a completely different formula, (and isn't even possible, if you look at FoV, transmitted light and DoF, any equivalence is physically impossible, you cannot maintain the amount of light, the aperture and DoF. It simply will not resolve.) No one has bothered with that, as it would be so pointless. Not everything can be simplified to fit the need to justify DoF as an important factor in lens selection, as hard as the proponents of elective DoF would try and make it so. The discussion has been going on since the 30s but, most people are concerned with getting enough DoF.
The whole denigration of small sensors as only equivalent to ƒ/8 or whatever is one of the most misleading misuses or abuses of limited information to promote bias ever inflicted on photography.
That my ZS100 achieves the DoF at 2.8 that an FF does at ƒ/8 or whatever, is a wonderful thing especially for those photographing in low light. The achievement of wide DoF at low light values completely exceeds any possible advantage in producing narrow DoF images. In technical terms, compared to larger format camera, small sensor DoF is an amazing technological achievement. Similar resolution, superior DoF, in much lower light.
ƒ/stops are calibrated for exposure. Not DoF. Full stop, end of discussion.