To me, what you descibe below is not the theoretical maximum SNR of "A"
DSLR/SCANNER.
You have described the theoretical maximum SNR of a specific existing
current system design.
Nothing wrong with what you are saying there but the key is you didn't
qualify your original
statement by saying on existing current systems designs, you just said
theoretical maximum SNR
of "A" DSLR/Scanner. 

I guess we are just talking two about different things because to me the
theoretical
maximum SNR of "A" DSLR/SCANNER has not been realized yet, that's why
its called theoretical
and technologies/designs are developed to try to achive real products
that come closer the theoretical maximums.
JCO

-----Original Message-----
From: Herb Chong [mailto:[EMAIL PROTECTED] 
Sent: Saturday, November 06, 2004 5:28 PM
To: [EMAIL PROTECTED]
Subject: Re: USAF target and resolution tests


a sensor has an intrinsic SNR. the output SNR depends on input SNR, the
gain, and the noise in the amplifier. the gain in a DSLR is a function
of the ISO setting. if the amplifier is perfect, then the input SNR is
identical to the output. if it's not, it's less. increase the gain and
the SNR decreases because the amplifier isn't perfect and because the
output is clipped.

Herb...
----- Original Message ----- 
From: "J. C. O'Connell" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Saturday, November 06, 2004 12:07 PM
Subject: RE: USAF target and resolution tests


> Youre still not clear, what is the "theorethical maximum SNR of a 
> DSLR/SCANNER at lowest ISO" mean according to you? Use said 
> "theoretical" which usually does involve mathematics and abstraction 
> and is exactly what you were comparing the real hardware against!


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