Flat frames are exposed images with a uniform exposed area. It is vital that the flat frames are shot with the same lenses (so filters, objective etc.) as well as with the same exposure of the motive (light frames).
With the help of these, flat frames brightness distortions like for example vignetting of the camera or dust inclusions (sensor spots) are removed.
Just like with dark frames a number of flat frame images will be taken to later be calculated together into a master flat.
The function stacking image sequences possesses a special mode for the stacking of flat frames just like it has one for dark frames.
On the left one can see the original image with a flaw in brightness in the top left half of the image.
The image in the middle is the shot flat frame (master flat). Here one can clearly see the flaw as a shadowing of the brightness.
On the right side one can see the calibrated result image of the flat frame. The flaw was entirely removed here.
This is the parameter for the setting of the flat frame correction:
Flat frame intensity
With the flat frame intensity one can adjust the intensity of the flat frame corrector, if there is the case of course that it turned out to be too weak.
Tip: Also the flat frames need to be calculated together with the dark frames. DENOISE projects 2 professional does this for you automatically.