Originally posted by Nicolas06 Sorry to say that you didn't get it. The crop factor of 3 is for the physical size of the sensor. It would apply if you were comparing a 12MP Q with a 12MP APSC. Or if we were speaking of a 24MP Q vs a 24MP APSC.
Now we were saying of the number of MP that remain if you go to Q framing with an APSC. This was say to be 2.6 MP. because well the APSC has 24. (24 / 3 * 3 = 2.66MP). This is direct application of this crop factor of 3 your speak of.
Up to this point you are correct.
Originally posted by Nicolas06 Now in term of visible detail the Q is able to display 12MP while the APSC on the same surface has 12MP. In surface that a factor of 4.5 (4.8 when MP are rounded to 2.5MP only). There 4.5 time less pixels in the APSC than the Q from the same surface.
This section is arguing with your (correct) arithmetic in the earlier section. You correctly determined in the first section that in a rectangle of any given size, the APS-C sensor will have 1/9-th (not 1/4.5-th) the number of pixels that the same-MP Q sensor will have
Originally posted by Nicolas06 If the pixel density is expressed not per surface area (2 dimension) but for a distance (like X pixels per mm and not X pixel per mm2), then you need to take the square root. This give you 2.12, Rounded to 2.2 coming from 2.5MP approximation.
This arithmetic is both unneeded and incorrect, because we already know that the Q sensor is 1/3-rd the linear dimensions of an APS-C sensor, so if each has the same number of pixels, the pixels on the Q sensor will be 1/3-rd as far apart as the pixels are on the APS-C sensor. Furthermore, your arithmetic is not relevant to your argument as you made it. Yes, pixels on a Q are closer together than they are on an APS-C camera, but I have never ever seen anyone use the word "crop" to describe that relationship; the correct term is "density", and its only relevance is that, as I have already mentioned, a lens designed for an APS-C camera may not resolve light down to the density of Q-7 sensor pixels.
Originally posted by Nicolas06 So yes I should not have said crop factor because it confused you even if this is a crop factor. But because this term has already another meaning, the pixel density factor maybe would be a better term.
If you try to honestly follow what has been said still this doesn't change the reasoning and doesn't mean the Q got suddenly better because my naming convention what bad, the computation itself is valid.
Words have meaning - that is why we use them. When you use the wrong words, most likely you will convey the wrong meaning.
Mathematics has meaning - when you perform the wrong calculations, you cannot expect someone who knows the true calculations to be impressed.
And, in any case, you are still not addressing my original comments. When I originally posted those pictures, they were in response to your comments singing the praises of fixed lens cameras and cell phones. My point then remains, that for the same cost as a fixed lens camera, I can buy a Q which provides flexibility not available from any fixed lens camera. I never claimed that the birding picture I posted was the best birding picture ever taken - in fact I even included the disclaimer that this was taken with an older prime lens I was testing (and found wanting) in the hope that it would resolve better than the newer lenses I have (because in my experience, some older primes are much sharper than some newer zooms). Yes, I could put the same lens on my K-30 and then crop the result in PP. In that case, my view through the viewfinder leaves me guessing whether I got anything good or not; only when I get into gimp will I know anything. My personal experience was that this method resulted in poorer pictures than the Q is giving me. And the truth remains that my Q-7 is simultaneously giving me better birding pictures than I ever got before, and better pictures from a pocket camera than I have ever got before. I carefully studied cameras of all types before buying this Q-7, and I confidently claim that no fixed lens camera will do both of those things for me.