Originally posted by BrianR With all due respect, that's how your choice of language usually looks to me, like calling changing focal lengths instead of distance the 'proper' way to get the same framing (on different sensor sizes).
Changing the distance to obtain the same framing, is just not acceptable if you want to compare apples to apples.
If someone wants to compare apples (a framing with one perspective) to oranges (same framing, but using a different perspective) then they are welcome to it, but it is much harder to make meaningful DOF comparisons between such different images.
If someone wants to deviate from the simple practice of comparing images which are identical in all image-relevant parameters for the purposes of discussing differences between sensor formats, they should have a better argument than just "
I can get the framing right by changing the subject distance and I don't care about the perspective change and its impact on DOF because I make the arbitrary decision to use the same lens on both formats for the same purposes". Continuing to use the same lens for the same purpose (e.g., portraits) despite a change in sensor size does not make sense from a photography aesthetics viewpoint and while it is something that someone could choose to do regardless, it just makes a comparison between sensor formats incredibly harder because one compares apples to oranges.
Originally posted by BrianR That kind of thing, to me, looks like you're deciding how other people should compare things.
I'm not deciding what an "apples to apples" comparison is.
I admit that I'm a proponent of "apples to apples" comparisons, in particular when people performing "apples to oranges" comparisons arrive at incorrect conclusions and then teach their incorrect findings to others.
Originally posted by BrianR 9 times out of 10 these misconceptions come from not clearly defining the parameters that are or aren't fixed in the comparison. Like "FF has more DoF than aps-c" and "FF has less DoF than aps-c" can both be true under the right conditions and many, many disagreements could be avoided if these conditions were made explicit from the outset.
I'm not sure about the "9 times out of 10" but in principle I agree.
BTW, the utility of the "equivalence" approach is that it takes out all variability of the parameters by enforcing an apples to apples comparison. There is no end to the scenarios one could construct to argue the case for one particular property holding for some format in specific circumstances. A pretty fruitless endeavour, AFAIC. Hence, it is very useful to provide a level playing field and then observe which differences are present, if any. That's what falconeye did and if only more read his articles and understood them, a lot of the fruitless discussions could be avoided.
BTW, I think
jsherman999's images do the talking in terms of FF advantages much better than I do. Granted, his compositions are really nice and he performs excellent post-processing, but still, I don't see images like that from APS-C cameras (including his former ones). If someone doesn't see the difference, I'm happy for them to forgo FF. I'm not happy for them, however, to tell others there is no difference or that FF is for "
shallow DOF portraits only".