Digital negative

John Sheehy wrote:

While I agree with the text of your post, I think that using an AC sine wave as a demonstration can actually reinforce false conceptions. The negative swing of the wave can be misunderstood to be the "dark" end as an analogy of light, but for an analogy of light, you would really need to use a rectified sine wave, as light does not have two directions as an AC sine wave can. There is no clipping of the dark end on a digital camera's sensor. The signal simply becomes less usable and distinguishable the smaller it is, against the fixed read noise, and the signal itself is highly textured by photon noise.

"Black" on a digital sensor would actually correspond to the X axis on your graph; not the most negative swing of the sine.

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John
http://www.pbase.com/image/55384958.jpg