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I am using a Nikon D5200. I intend to do some image processing on the raw images shot with the camera. But I am encountering a problem when I read the raw images using GNU Octave. Rather than giving bit depth of 16 (since the .NEF are shot at 14-bit depth), the result is just a 8-bit array. What might be the problem?

imfinfo("/media/karthikeyan/3434-3531/DCIM/100D5200/DSC_1094.NEF")

ans =

scalar structure containing the fields:

Filename = /media/karthikeyan/3434-3531/DCIM/100D5200/DSC_1094.NEF

FileModDate = 10-Oct-2016 18:10:02

FileSize = 26735420

Format = DCRAW

FormatVersion =

Width = 6036

Height = 4020

BitDepth = 8

ColorType = truecolor

The result from exiftool is as follows:

exiftool DSC_1094.NEF | grep -i bit

Bits Per Sample : 14

I am using Ubuntu 14.04, Octave 4.0.3.

karthikeyan
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    The first time you use `imread`, `imfinfo`, or `imread`, do you get a warning similar to "your version of GraphicsMagick limits images to 8 bits per pixel"? – carandraug Oct 13 '16 at 10:54
  • @carandraug No I rebuilt Graphics Magick with quantum-depth 16 bit. Read a .TIFF which is 16-bit depth and `imfinfo` yields right result. .NEF does not seem to. – karthikeyan Oct 13 '16 at 19:35
  • well, Octave relies on GraphicsMagick to read the images. I guess it is possible that GraphicsMagick NEF reader still only reads 8 bit. Try `gm identify -verbose DSC_1094.NEF` and check. Then report a bug with Octave if `gm identify` reports the right info, or with GraphicsMagick otherwise. – carandraug Oct 13 '16 at 20:37

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