D5500 NEF(RAW) too dark compared to JPG, which pixel value is right?

[OldSkyEyes]

Hi,

I'm just trying out pixinsight with a trial license. (I like the easy menu font sizing for my bad eyes.)

When I open a Nikon RAW file of my D5500 it is a lot darker.
STF Autostretch helps a bit but clearly not the same as what Nikon had in mind.
RAW/NEF looks ok in the Nikon Capture NX-D and windows viewer.

Here you find an example NEF file with JPG how it should be. (NEF 14bit)
https://1drv.ms/f/s!AutrcYXPZoBZcOLcYna95qErv-4

I want to know what the real sensor value is that I can use to process further??

Thanks!

If I do a Fourier on this picture I see a clear difference between the jpg and the NEF, makes me think that maybe something is wrong with the raw decoding, just guessing.
(pictures to show the difference attached.)

[vicent_peris]

Hi,

There's nothing wrong, it's just that PixInsight does not apply any stretching to your image (the other software packages are doing it automatically). To really show the real sensor values, follow this steps:

- Go to the Format Explorer.
- Open the DSLR_RAW format preferences.
- Press the "Pure Raw" button to change the settings.

Now, open again the NEF file. It will show the purely raw image without any stretching and even without any debayering. These are the true pixel values coming from the sensor. The other software packages are automatically modifying the original pixel values of the image.


Best regards,
Vicent.

[OldSkyEyes]

Maybe but shouldn't white be white??

I took an over exposure to have all pixels at maximum.
But it is still gray 14bit looks more or less ok for max 16350 but I think the program thinks that 16bit is maximum.
and white of the JPG 16bit is 65535 (2^16-1) is correct.

In the attached picture one is CFA the other is RGB

[vicent_peris]

Yes, that's because an image cannot be stored with a 14-bit depth. NEF files are stored as 16-bit images, the saturation point being at the 2^14 ADU value. These are the true pixel values coming from the sensor. If you want to show those value as white, just go to HistogramTransformation and place the white point to 0.25.

Best regards,
Vicent.

[OldSkyEyes]

Any idea which kind of transformation is still missing to end up with the same look as the JPG?
I play with this curve but no close match is possible, looks like the picture lost resolution.

[vicent_peris]

Hi,

Usually the JPEG images generated by DSLR are actually processed images. You cannot get exactly the same image from the RAW file if you don't know which kind of processes have been applied by the camera. The only thing that I can see in that image is that the JPEG image has a gamma curve applied, instead of a midtone transfer curve. You can try to apply a gamma curve with AutoHistograms, but for sure you'll need some more processing steps: probably a color saturation enhancement and some sharpening. My Panasonic camera also does some additional color and geometry corrections depending on the lens.

Best regards,
Vicent.