FLATS !

[pscammp]

Thanks Tobias, please don't apologise,
   Turns out that there was a delay to me & Mrs going to a family gathering today so I had the chance to run this idea.....

Did exactly what you suggested using '0->0.125 and 1->0.875' in 'CurvesTransform' and the result certainly is better but
I appear to be left with a nasty colour cast in the image, this appears as Green in the center and a magenta colour around
the outside of the image where the white illumination used to be. This required lots of DBE to remove with Tolerance set at
around 2.0. If I use 'ConvertToGreyscale' on the Master Light then It looks perfect with ref to corner over illumination which
is a good thing, problem is, using DBE this aggressively, is this going to be potentially removing some valuable signal in the
process ? 

See attached pic

Regards
Paul

[pscammp]

Just a thought !

Attached is a pic of the histogram of one of the flats.

Is it possible that the colour casts in the above image is related to the R G & B channels not being lined up with each other  ??

Regards
Paul   

[TobiasLindemann]

Paul,
do you have done flats for all channels? Is looks like the flats don't fit for all channels. But this can be a cause of the transformation. This method is not based on math but on try and error. So it may work for one channel, but for the other channels you may need other in- and outputs. I don't know on which channel I worked on, but I think the green channel has to be pushed on the edges a bit. So the CurvesTrasformation on the green flats should be less aggressive. Maybe an output of 0.1 and 0.9 do a better job, but this is  try and error.
Though I think the color-gradients are no real issue and can be flattened by DBE.
Tobias

[biosif]

pscammp.
I downloaded and processed your files. Flat files we examined are ok for me. Dark files in the upper left corner there is a look of light that appears on the final image. I processed all files with Percentile Clipping and combination Percentile Average. I put a screenshot of your files.

[biosif]

Hi.
Also to analyze CCD Inspector Light show all images that capture below, and indicate a problem in the upper left corner.

[pscammp]

biosif,

The glow in the upper left corner is Amp Glow. This is present in all images over around 3.85 sec long from my camera.

When processing I have to ensure that 'Optimise' or 'Optimise Dark Frames' is disabled. Providing this is disabled then
the Amp Glow is removed by the Darks.

Cheers
Paul

[biosif]

The process i have used is so.

[pscammp]

biosif,

In the 'Global Options' section, disable 'Optimise Dark Frames', this will take out the Amp Glow

Paul

[biosif]

Hi.
I have reprocessed the image without dark optimization and the image is so.
I think is ok. What you say?

[pscammp]

biosif,
    Nice.....Except all the corners are over illuminated, this is what we are trying to solve here !

Paul

[TobiasLindemann]

Paul,
sorry I just realized it is a color-camera and it has to be debayered. Before I thought you have uploaded just one channel of your series  . So you certainly have only one type of flats and your hardly can calibrate the channels separately.
Tobias

[pscammp]

LOL

Tobias, yes, one shot colour camera. What effect do you think it would have if I Debayered the Master Flat and converted it to Greyscale and then CurvesTransform it, would this possibly make a difference ?

Regards
Paul

[TobiasLindemann]

hm, I don't think it is a good idea because one meaning of the flats is to correct the difference in pixel-sensitivity. If you debayer the pixels they are interpolated and not the originals. ...but maybe have it a try.

[pscammp]

Tobias,
   Don't think I will try that then   

[pscammp]

gvanhau,

So what's your suggested workflow then ?

Thanks
Paul