Quote:How about stop talking bullshit and prove with showing, linking or writing a formula in which a given area does matter and changes ISO or sensitivity from a larger to a smaller sensor. And YES a exposure meter does tell me this sort of stuff because normal use of it is to choose a shutter speed or an aperture and an ISO number. You're always trying the same boring trick, using a distraction and questioning common sense. I don't know any exposure meter where I have to put in a film size or sensor size into the equation.
And the fact that a sensor is no film but is dealing with ISO, shutter speed and aperture as if it were a film doesn't matter. Basics is, two different sensors will need different ISO but a single sensor will be at the same parameters if you use it full frame or half frame. Any math acrobatics is caused by different sensor technologies, but not by sensor size. By comparing sensors, we need to stay in the same type, not compare X-Trans with Bayer or Foveon. And it's the topic of "area" which is discussion base, not the sensor type.
Anyway is this whole ISO thing metaphorical as sensors behave differently and their output of data is influenced by tons of other parameters. One stop faster remains one stop faster.
Take the EOS 5Ds (50mp) and the 7D II (20mp).
They have roughly the same pixel density thus roughly the same noise level per square-millimeter - give or take a little.
However, when comparing these cameras you have to do that on identical grounds - at the SAME megapixels.
Thus you have to downsize the 50mp to 20mp. As a consequence, the noise level decreases substantially - by roughly "1 stop" (a little more). Vice versa this also means that the 5Ds (@ 20mp) is about as good at ISO 800 as the 7D II (@ 20mp) at ISO 400.
So combined with a lens the 5Ds (@20 mp) is as fast with a f/4 lens (using ISO 800) as the 7D II (@ 20mp) with a f/2.8 lens (using ISO 400).
Is that so hard to understand ? You don't take picture with a lens. You take pictures with a camera plus a lens.
Feel free to point to the flaw in this logic.