On 1 May 2014 14:32, Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
> I started digging into this image stacking stuff for deep sky photography
> and immediately started running into terms I didn't understand as in this
> passage
> ------------------------------------------------------------------
> 4 Capture your light and calibration frames
>
> Start your imaging run, aiming for as many images as possible. Unless you
> already have a library of bias and dark frames (at the correct exposure
> length), leave time for these. Flat frames must be taken on the night or
> the next day without touching the camera or focus.
> ------------------------------------------------------------------
>
> I have no idea what "bias" and "flat" frames are but assume that I do know
> what a "dark" frame is. I assume that a dark frame is an "exposure" taken
> with the shutter closed or sensor otherwise blocked from light. It's to be
> taken at the same exposure time as other shots where you want to subtract
> digital noise from a long exposure.
It's explained in the FAQ - link is in the pane on the left hand side.
Flat frames compensate for unevenness of response across the sensor, bias
frames compensate for the small spurious signal which you still get from
reading a completely unexposed sensor.
Ian
--
Stand firm for what you believe in, until and unless logic and experience
prove you wrong. Remember: when the emperor looks naked, the emperor *is*
naked, the truth and a lie are not "sort-of the same thing" and there is
no aspect, no facet, no moment of life that can't be improved with pizza.
-Daria Morgendorffer
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|