Okies, we'll try to sort this out... :-)
Thanks for that - I think we now pretty much agree on the theory.
However, I think you may have missed the broader point that I was trying to get across in the first place, so I'll briefly summarize that now.
There is a commonly held misconception that the image noise performance of a compact point-and-shoot camera can be significantly improved simply by using a larger sensor, and presume that Wayne had this notion in mind when he suggested that Canon should use a larger sensor than the 1/1.7" in the G11, if and when they bring out a G12.
From my reading on the net, there is an almost universally held myth (or at least, highly misleading explanation) that a larger sensor collects more light simply because it has a larger surface area, and the net abounds with analogies where if you place a larger bucket (sensor) in a rain of photons, then "obviously" the larger bucket (sensor) will catch more photons. It is only a small step from there to conclude that if camera manufacturers had the good sense to fit larger sensors into compact cameras, then more light would be collected, with a subsequent reduction in image noise.
The problem with this reasoning is that, depite popular myth, the amount of light falling on the sensor does
not fundamentally have anything to do with the size of the sensor, but is is instead set by the aperture area (and therefore physical size) of the lens. We both agree fully on this point. In your words:
(Amount of light striking sensor) = (Field of view) x (Aperture Area)Note that the size of the sensor does not come into it, exploding the myth that the sensor size is directly responsible for collecting more light.
Once it is understood that it is actually the physical size of the lens (aperture area) that determines how much light is incident on the sensor, rather than the sensor size, it becomes obvious why camera manufacturers do not waste their time putting large sensors into compact cameras that must necessarily have compact lenses, hence my previous example of how essentially nothing useful is achieved if you hypothetically try to improve the performance of a G11 by simply slotting in a lager sensor.
While nothing I have said to date is incorrect, it turns out that a larger sensor permits the use of larger lenses, which therefore gather more light onto the sensor and decrease image noise, which is a very good reason why SLR and professional camera use larger sensors. As yet I have not told the whole story, but have probably monopolized and distorted Waynes thread for long enough. Sorrry about that, Wayne.
I should probably start a new thread entitled "Myth of the large sensor compact camera", and continue the discussion
Cheers, Col
