Re: [APML] a short note on film flat fielding

[Jerry Lodriguss <jerryapml@astropix.com>]

Hi Wei-Hao,

Yes, that answers my questions.

Thanks, and good luck. I'm looking forward to seeing more pictures.

Jerry


>You are perfectly right that there is no RF at all in the daylight shot
>of flat fields.  The RF only exists in the real images taken at night.
>The RF and the nonlinear HD curve, alter the shape of the illumination
>pattern.  That is all why I cannot use the daylight shot directly as
>flat fields, unlike CCD flat fielding.  I have to use selected background
>regions from the real night-sky shot to modify the shape of the daylight
>shot.  So the modified flat field has the same values as the HD+RF altered
>illumination pattern.  This modification absorbs all the differences in
>HD curves and RF of different films at once.
>
>Hope this answers the question.

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