Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Topics - CraigNZ

Pages: 1 2 [3]
31
General / Open DSLR raw file shows wrong pixel values
« on: 2015 July 08 23:47:54 »
I am using a Canon 60D and acquired some RAW images at ISO 800.
I set Format Explorer|DSLR_RAW to Pure Raw.

When I open a .cr2 file (canon raw) and use Process|Image|Statistics|14 bit setting it shows the mean as 528.6 and maximum as 3826.6

When I open the same image with AIP4WIN and again use RAW with no conversion I get mean as 2114.36 and maximum as 15307.

The AIP4WIN figures are correct.  These are the raw pixel values as verified by several other programs and makes sense because Canon has a bias of about 2000 on each pixel.  The max value is also correct because a saturated pixel will be just shy of 16383 the maximum value for a 14 bit camera.

So why is PI showing a completely different value?  I am guessing that it is applying several correction factors that appear in the cr2 file supplied by the camera rather than the real raw pixels.  I believe the fault is in DCRAW and maybe some setting not being set.  Maybe a Hint setting would fix this?

The reason I bring this up is because I took images at 30 sec, 60 sec and 300 sec and they all show the same detail after calibration, debayering and integration.  The statistics report shows the same values with a very slight difference.  That means there is no point in combining the images to expand the dynamic range because they are all the same.

I believe all the pre-processing of the raw images should be done with true raw pixel values so that down the stream we have the full dynamic range available using something like HDR.

Pages: 1 2 [3]