Quote:
Originally Posted by sjastro
You are not recording any faster at f/4. The amount of information in the image is a function of the diameter of the mirror (or lens). You are collecting the same number of photons at f/8 at the same exposure.
The important difference is in the pixel scale. The effects of camera noise such as read out noise and thermal noise can be more easily discerned in faint objects as one increases the f/ratio. That's because the pixel scale allows the noise to be resolved in the image.
That's probably where the confusion lies. The apparent lesser noise in a smaller f/ratio image is falsely attributed to a stronger signal.
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OK, So is field of view the only reason that we should choose one F ratio over another or would choosing apparent less noise be valid also.