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PeartreeStudios
Known Participant
June 9, 2020
Question

Does the DNG spec support quad bayer type filter pattern?

  • June 9, 2020
  • 1 reply
  • 2236 views

I'm looking to use the DNG SDK to write DNG files from quad bayer RAW image data but I'm not sure if DNG actually supports this bayer pattern.

 

I have found DNG sample files from cameras which use quad bayer sensors but analysing the DNG/TIFF tags they're not correctly reporting a quad bayer pattern.

 

Does anyone know if DNG actually properly supports quad bayer?

 

 

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1 reply

S
sandy_mc
Inspiring
June 10, 2020

Some more detail would be helpful here - what do you mean by "not correctly reporting a quad bayer pattern"? Quad bayer is just a 16 pixel bayer pattern.

P
PeartreeStudiosAuthor
Known Participant
June 17, 2020

I have a couple of sample DNGs from the DJI Mavic Air 2 which features a 48mp quad bayer sensor. At 48 megapixels it outputs quad bayer DNG files at ~90mb in size.

Running dng_validate on them does not however reveal them to be a quad bayer sensor:

CFARepeatPatternDim: Rows = 2, Cols = 2
CFAPattern:
    Red      Green
    Green    Blue
CFAPlaneColor: Red Green Blue
CFALayout: Rectangular (or square) layout

I have also checked other quad bayer sensor cameras capable of saving to DNG and they also report a "normal" bayer 2x2 pattern. So I'm trying to determine if the DNG spec actually has a way of specifying a quad bayer pattern.

If it does, great - but then why are all these quad bayer cameras not doing that?

K
kmilos
Participating Frequently
June 23, 2020

There is a also the possibility that the sensor/camera internally converts ('remosaics') the quad to the regular 2x2 Bayer pattern before saving to a DNG file which can then be consumed by many existing raw processing SW that doesn't understand anything else but 2x2 Bayer (or X-Trans) as of today. The DNG spec itself of course allows for storing other patterns via the CFARepeatPatternDim tag in theory.

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