newbie question on ASA speed settings

On a Canon D30, for instance, I'm trying to understand what the ASA speed
settings
really do. Is there anything optically/electronically different about the
way the data is
recorded, or is this simply a parameter for influencing the various
automation modes?

thanks
bill

"bill a" wrote in message
m...
On a Canon D30, for instance, I'm trying to understand what the ASA speed
settings
really do. Is there anything optically/electronically different about the
way the data is
recorded, or is this simply a parameter for influencing the various
automation modes?

thanks
bill

it's an amplifier to boost the signal, higher ISO (ASA) the more the gain,
and also the noise.

so the noise is the (no free lunch) tradeoff like grain size for film.
that explains it.
thanks,
bill


"dylan" wrote in message
...

"bill a" wrote in message
m...
On a Canon D30, for instance, I'm trying to understand what the ASA speed
settings
really do. Is there anything optically/electronically different about
the way the data is
recorded, or is this simply a parameter for influencing the various
automation modes?

thanks
bill

it's an amplifier to boost the signal, higher ISO (ASA) the more the gain,
and also the noise.

so the noise is the (no free lunch) tradeoff like grain size for film.
that explains it.

Exactly. It's like using a film with faster speed. More grain.

bill a wrote:
so the noise is the (no free lunch) tradeoff like grain size for film.
that explains it.


There's no free lunch, but it's not as bad a film grain though.

Film grain looks noisier (z) and is larger (x,y) as the ISO goes up.

Digital noise does not get larger in x,y as it is constrained to its
fixed pixel size. The noise in digital is in amplitude (z) only.

Hence digital usually looks cleaner than film as ISO goes up.

Cheers,
Alan

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