I think the word "equivalence" should be banned as it's an instant flame bait. :blink:
My 2 cents though: shallow DOF is the bane of my existence. :mellow: Well, maybe not so tragic, but I don't like being forced to stop down a lot just to get a meaningful part of the subject (or a group thereof) in focus. That something isn't blurred into an unrecognizable mess doesn't mean it's rendered in a useful way; half-soft image (or parts thereof) is still that - soft and therefore not beneficial to displaying the subject (if it falls into such an area). Therefore shallow DOF shouldn't be peddled as an universally desirable effect.
Not that there's that much difference (that you would be able to see in a blind test) one stop apart, or between APS-C and FF crops shot at the same aperture (and so being one stop apart, by this logic). Therefore: peace.
P.S. I may be a little thick but does anybody really calculate the scene in that way - starting with "I need a precise focal length X and aperture Y, if I can't get that it all goes to hell"? I start out by looking into the viewfinder and deciding if I like what I see, if it's too narrow I don a wideangle, if it's too wide I don a telephoto. If I don't get enough DOF I try to stop down (but more often than not I just shoot, I don't usually get gross errors). That my 16mm f/4 lens becomes (or doesn't become) a "21mm f/5.2" or whatever else means zilch to me - I don't think in these terms, I just shoot.
My 2 cents though: shallow DOF is the bane of my existence. :mellow: Well, maybe not so tragic, but I don't like being forced to stop down a lot just to get a meaningful part of the subject (or a group thereof) in focus. That something isn't blurred into an unrecognizable mess doesn't mean it's rendered in a useful way; half-soft image (or parts thereof) is still that - soft and therefore not beneficial to displaying the subject (if it falls into such an area). Therefore shallow DOF shouldn't be peddled as an universally desirable effect.
Not that there's that much difference (that you would be able to see in a blind test) one stop apart, or between APS-C and FF crops shot at the same aperture (and so being one stop apart, by this logic). Therefore: peace.
P.S. I may be a little thick but does anybody really calculate the scene in that way - starting with "I need a precise focal length X and aperture Y, if I can't get that it all goes to hell"? I start out by looking into the viewfinder and deciding if I like what I see, if it's too narrow I don a wideangle, if it's too wide I don a telephoto. If I don't get enough DOF I try to stop down (but more often than not I just shoot, I don't usually get gross errors). That my 16mm f/4 lens becomes (or doesn't become) a "21mm f/5.2" or whatever else means zilch to me - I don't think in these terms, I just shoot.