Started Apr 15, 2012 | Discussions thread
Detail Man
Forum ProPosts: 14,837
Re: Clarification: Effects of maximizing Exposure upon (Read Noise) SNR.
In reply to Detail Man, Aug 2, 2012

Detail Man wrote:

Detail Man wrote:

Vlad S wrote:

2. To increase signal and thereby improve S/N ratio

Right. Due to the ratio of Signal divided by the vector-summation of Photon Shot Noise, and Read Noise sources ...

For those who are unaware of the math:

The following equation is commonly used to calculate CCD camera system signal-to-noise ratio:

SNR = ( PQet ) / ( SQRT ( PQet + Dt + (N[r])^2 ) )

... where P is the incident photon flux (photons/pixel/second), Q(e) represents the CCD quantum efficiency, t is the integration time (seconds), D is the dark current value (electrons/pixel/second), and N[r] represents read noise (electrons rms/pixel) .

Careful examination indicates that the equation above is simply structured as a ratio of total signal generated during the exposure time divided by the combined noise attributable to the three primary noise components. The noise terms are not correlated, and the denominator incorporates appropriate values for each noise component: the square-root of the signal accounts for the photon noise, dark noise is equivalent to the square-root of the product of dark current and integration time, and the square-root of N(r)-squared corresponds to the read noise component .

Note : Read Noise is expressed in RMS units. Note the square-root taken of the denominator terms

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