Canon 20D - ISO 100 performance?

wrote:

In message ,
Alan Browne wrote:


wrote:


In message ,
Alan Browne wrote:


Maxxum 7D uses the same sensor line and goes 100 to 3200.



These numbers are fairly arbitrary. I would not be concerned about a
camera only going down to "ISO 200", if you can set the camera to "ISO
200" and shoot just like it was ISO 100, without blowing reasonable
highlights, or if you could do it at ISO 125. Different camera metering
system have different ways of utilizing the 12 bits of RAW data.


In D/SLR's the metering system does not use the sensor data.


Your definition of "utilizing" is a bit narrow, don't you think?

No.

"Utilizing" does not mean "deriving directly from".

Your phrasing, not mine. The meter just measures the light presented to
it to set exposure for a given (notional/nominal) sensitivity. From
your own experience with various Canon's it is hardly consistent.


The design of the camera acknowledges the absolute sensitivity of the
camera, and how sensor exposure maps to the RAW data at a given ISO.

From your own explanations it would appear that Canon have not settled
on a common mapping of what that should be...

Cheers,
Alan


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