nospam wrote:
In article , Nan
wrote:

In other words either the ISO 100 of one camera is in reality an ISO 80
or an ISO 125 and the other camera is accurate, or both cameras deviate
a bit from the ISO.

lots of cameras cheat.

Is it a cheat or a lie ?

Neither, I think. As I understand it, the ISO standard
gives manufacturers some latitude to choose how they
want to set the ISO scale for each particular model. For
example, if the sensor's native sensitivity measures,
say 139, the manufacturer has the flexibility under the
ISO standard to call that ISO 100 or ISO 200, and then
adjust the metering to give the appropriate exposure values
for the 'adjusted' ISO.

it's not about native iso, it's about what the camera does when set to
a specific iso, such as 100, 125, 160, 200, etc.

some cameras cheat. that's just how it is.

No cameras "cheat". The Standard basically says that any method
the manufacturer likes, is okay. That makes cheating not only
unnecessary, but virtually impossible.

And in fact it's a system that has turned out to work well
enough over the years!

--
Floyd L. Davidson http://www.apaflo.com/
Ukpeagvik (Barrow, Alaska)