tornado33
04-12-2005, 09:45 AM
Hi all.
At first I was dissapointed with the huge amount of dark noise, it was one
of the warmest nights that ive ever dont a 15 minute ISO 1600 shot at.
However I decided to try IRIS onge again, and the result was less noise even
than Photoshop, and further, an old flat field that I used some weeks ago
helped flatten the field too. I then stretched the levels in PS then tried
subtracting a dark in PS again, but I noted as most of the hot pixels were
red, I went into levels and cut right back the blue and green channel. That
got rid of the dark spots I would otherwise get. I combined the layers, I
did this to both shots I took then stacked them in PC as normal. Considering
the initial high amount of dark noise due to the warmish night Im happy to
have got rid of as much noise as I have. I think the important thing is to
make sure the dark frame is the exact same length as the light shots. Note
In IRIS theres anso a "deviant pixel removal' proceedure but I couldnt do
that as it found too many deviant pixels due to the rather long (15 minute
ISO 1600) shots.
Anyway to summarise its 2 x 15 mins ISO 1600, MPCC, UHCS filter
Flatfielding, DF subtracted in IRIS, then DF red channel subtracted again in
PS.
Scott
At first I was dissapointed with the huge amount of dark noise, it was one
of the warmest nights that ive ever dont a 15 minute ISO 1600 shot at.
However I decided to try IRIS onge again, and the result was less noise even
than Photoshop, and further, an old flat field that I used some weeks ago
helped flatten the field too. I then stretched the levels in PS then tried
subtracting a dark in PS again, but I noted as most of the hot pixels were
red, I went into levels and cut right back the blue and green channel. That
got rid of the dark spots I would otherwise get. I combined the layers, I
did this to both shots I took then stacked them in PC as normal. Considering
the initial high amount of dark noise due to the warmish night Im happy to
have got rid of as much noise as I have. I think the important thing is to
make sure the dark frame is the exact same length as the light shots. Note
In IRIS theres anso a "deviant pixel removal' proceedure but I couldnt do
that as it found too many deviant pixels due to the rather long (15 minute
ISO 1600) shots.
Anyway to summarise its 2 x 15 mins ISO 1600, MPCC, UHCS filter
Flatfielding, DF subtracted in IRIS, then DF red channel subtracted again in
PS.
Scott