batch processing warning message

[whwang]

Hi,

I got a warning message: "No correlation between the master dark and target frames (channel 0)"
Does any one know what the message means?  Should I worry about it?

Cheers,
Wei-Hao

[Geoff]

Do a search on "no correlation". You'll be inundated with hits.
Geoff

[whwang]

Thanks, Geoff.

Looks like it implies that no dark subtraction will be done in the calibration, which seems quite odd to me.  My camera is Nikon D800 (hacked to restore its true dark level), which is known to have low dark current.  The environment is cool (2-8 deg C) and the camera is not actively cooled.  I can believe that the dark has very small contribution to the pixel values, but should not be zero.  Because my darks are taken under controlled conditions that are very close to the condition of the light frames, I would say that the required scaling factor should be very close to 1.0.  On the other hand, after doing the search you mentioned, I saw that Juan thinks we should trust the judgement of dark optimization.  According to the dark optimization, 0 is the right scaling factor.  This is very puzzling. 

Any insight on this?

Cheers,
Wei-Hao

[Don]

Hi Wei-Hao,

It looks like it's a flat that generated the "no correlation" message.  That's not so unusual with sub 1 second flats.  When I don't see that message in flat calibration, the correlation factor is always very low.

Don

[whwang]

Hi Don,

Thanks!!  I did not realize it is for flat.  I just paid attention to the warning message but not anything else.  It now totally makes sense. 

Cheers,
Wei-Hao