Editing "Anamorphic" dng footage

[Volumetrik]

Hello, I am using DNG sequences produced from magic lantern firmware on my Canon 5DIII.

This footage is special in the sense that it uses pixel binning 3x horizontally but not vertically effectively creating an output file size of : 1920x2340. This file is then stretched by a factor of three horizontally in NLE's to produce 5760x2340 footage.

I looking to skip the stretching post-process work by modifying the DNG's metadata beforehand to have a 5760x2340 file ready to go.

I know that the DefaultScale parameter is the one to change and it works in AE and ACR. However when imported in Premiere, it is still compressed and requires manually de-squeezing.

My question is : Can I change the metadata further than just the DefaultScale to achieve an essentially "native" 5760x2340 file ?

From my understanding I would need to change these parameters :

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Image Width
Default Scale
Default Crop Size
Active Area
Image Size


From the errors I've had, it seems I would also need to change the parameter StripByteCount to 26956800 ?

So far I have the latest 12.03 ExifTool in a folder with a dng image called ana.dng. Using this code :

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exiftool -DefaultScale="3 1" ana.dng

I get the result :

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Nothing changed in ana.dng
    0 image files updated
    1 image files unchanged


Here is a complete transcript of my CMD prompt :

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C:\Users\Chalet\Downloads\exiftool-12.03>exiftool -DefaultScale="3 1" ana.dng -v2
Writing SubIFD:DefaultScale
======== ana.dng
Rewriting ana.dng...
  Editing tags in: IFD0 SubIFD TIFF
  Creating tags in: IFD0 SubIFD TIFF
  FileType = DNG
  FileTypeExtension = DNG
  MIMEType = image/x-adobe-dng
  Rewriting IFD0
  Rewriting ExifIFD
  Copying 1 image data blocks
Nothing changed in ana.dng
    0 image files updated
    1 image files unchanged


I'm sure I'm doing something wrong and I tried searching around for users that had the same errors as me and I found very little information on this specific issue. That is why I am posting this.

So I guess to summarize :

1: Is the "native" 5760x2340 thing even possible for my use case ?
2: What am I doing wrong on the DefaultScale parameter to get an unchanged file ?

Thanks a lot,

Max

[Phil Harvey]

Hi Max,

First, DefaultScale gets written to the SubIFD by default.  Your DNG didn't have a SubIFD (apparently), so you should specify another location where you want to write it.  Use exiftool -a -G1 FILE to see the existing tags and where they are located.

Second, you can't just change the StripByteCounts without changing the actual image data to match.  And ExifTool can't be used to change the image data.

I would guess that what you want requires some image manipulation, but that's just a guess.  I've never tried to do something like this myself.

- Phil