[Brightcolours]

[quote name='mst' timestamp='1316878864' post='11818']

And it would have to expose a much larger film area (and therefor need more light). But, what's more important and what ISO really is about: it would take the same exposure time in both cases.

[/quote]

With film the ISO would be based at exposing the same area unit the same. With the smaller film, the grain would be the same.

With different sensors, the pixels (the grain) are not the same size. Hence, ISO is not what ISO used the be (not about how sensitive film is) anymore. Most clearly demonstrated by my former example, the 12mp D3 and the 12mp E-30.

One could say that if the D3 uses an ISO 100 sensor, the E-30 uses an ISO 400 sensor pushed two stops. With an E-30 ISO 100 is equivalent to ISO 400 on a D3, Because the image elements get 1/4 of the light exposure.



So, yes, ISO is quite meaningless (not about how sensitive the sensor is in any way). And it has no place in lens equivalence anyway.



[quote name='mst' timestamp='1316878864' post='11818']

That's all relevance the ISO number has to me as a photographer. Same ISO, same aperture -> same shutter speed. Regardless of the sensor size.



-- Markus

[/quote]

And how is that different to what I said? I said exactly that. It has no relevance in real exposure anymore, as it is not about sensor sensitivity, as it was for film sensitivity. Its only relevance now is to make it simple for photographers.



Does not change in any way that is you want to use EQUIVALENT settings, to create similar images, you need to use:

* An equivalent focal length for similar filed of view (which in the 150mm case is about 400mm for FF vs Nikon 1)

* An equivalent f-value for similar aperture and DOF (which in the 2f.8 case is about f8 for FF vs Nikon 1)

* An equivalent ISO setting (for similar exposure of the "grain" (the sensels) and similar exposure time.