Thanks for the interesting link. But I have a problem with his
description of large pixels on MF cameras being large photon buckets and
taking a long time to fill due to their size and thus making a
difference in ISO measurements. Makes no sense to me at all.
Ignoring vignetting by the lens, the number of photons striking a given
area is a constant for a given illumination level. If the pixel is
large it should make no difference at all since the larger area also
captures more photons in a given time interval than a small pixel.
Consider a bucket that is 1 foot in diameter and 1 foot deep. Also
consider a bucket that's 2 feet in diameter and 1 foot deep. Now place
them both under the tailgate of a dump truck carrying sand. Dump the
load onto the buckets. Which one takes longer to fill?
Maybe the key is understanding what it means to "saturate the sensor"
and that this is somehow a function of area independent of the number of
photons striking a given area.
Chuck Norcutt
On 9/26/2012 11:01 PM, Moose wrote:
>
> On 9/25/2012 11:39 PM, usher99@xxxxxxx wrote:
>>> And how does that affect manual mode?
>> Dr. ISO is traveling but I don't think manual mode is affected per se
>> as the cam of course operates on what the "true"
>> ISO actually is.
>
> Man, I hope that's not me! However, Ctein happens to have opined on the
> subject in what I find to be useful ways today
> on TOP.
> <http://theonlinephotographer.typepad.com/the_online_photographer/2012/09/why-iso-isnt-iso.html>
> Perhaps he will
> convince you that there is no "true" ISO. :-)
>
> I know what I'm doing with exposure amounts to much the same thing as what he
> describes as 'camera ISO'. The E-M5 IS
> different in some ways than the Canons. It seems for best results, I need to
> pay more attention to EV compensation.
>
> It's All Relative Moose
>
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