Question about DNG's

[Pith]

Hello Guys!
I downloaded ML for my 5D Mark III a week ago and now trying to edit some test footage I shot with it.
I researched forum and read information available, but because of the huge amount of it have a mess in my head and I'm maybe missing some key points of the workflow.

So, here's my question:
when I use MlRawViewer 1.3.3 to convert my .mlv files, I get cinemaDNG's which are roughly 2MB each but when I convert the same files with MLVFS, CinemaDNG's I get are roughly twice as big - around 4MB. Are DNG's exported by MLVFS of higher quality or what's the difference?

And generally I'm somehow confused about DNG file format. For example how can one differentiate regular DNG from CinemaDNG? As I read, CinemaDNG's have embedded metadata which is used by Resolve or AE but how can I see it? If I right-click>Properties on the files, the information that comes up, looks pretty much the same.
Or How do I tell if the DNG is 12bit or 14bit?
I am using Mac OSX Yosemite, if that's important.

I will be very thankful if someone will make this clear to me

[dmilligan]

MLRawViewer uses lossless compression on the CDNGs. MLVFS does not use compression => it doesn't make any sense. The virtual CDNGs aren't actually taking up any "real" space. Yes, they do have a "size" reported by the OS, and if you were to copy them out of the mount and into the "real" filesystem then they do take up real space, but MLVFS wasn't really intended for this purpose. If you leave them in the "virtual" filesystem, they aren't taking up any extra disk space, when programs try to read them, their data comes from the original MLV file, so it's actually just the original MLV file that is taking up space.


DNG vs CDNG

It's a bigger difference than just metadata (and at the same time, there's really no difference, read on). CDNGs typically don't have an embedded preview "IFD" (sub image), they only have the main image. Most DNGs provide an embedded preview (the DNG spec recommends, but doesn't require this). None of the CDNG tags are actually required by the CDNG spec, but most apps (Resolve/Premiere) require them. The only one that's really needed is the frame rate tag (51044), though, the timecode tag is typically included as well.

Strictly according to the specs a normal DNG can be a "CDNG" with out really any difference (because none of the tags are actually required by the spec). So when we speak of "CDNG"s here, what we really mean is "a CDNG that is compatible with Resolve/Premiere".

Neither Resolve or Premiere support the full "CDNG" specification, they merely support some subset of it that is basically CDNGs produced by some specific camera. (I think this is stupid). The CDNG specification technically allows any bit depth, but again Resolve/Premiere don't seem to support 14 bit (native bit depth of Canon), so we usually convert up to 16 or down to 12.

So, how do you know if it's "CDNG" well since we've basically defined that as being able to be opened by Resolve/Premiere, you know it's CDNG if you can open it in Resolve/Premiere. (otherwise it's not, though technically speaking, it may actually conform to the actual CDNG specification)

If you'd like to see all the actual metadata tags, I recommend using exiftool. Once you've installed exiftool, you can use the following command to see all the tags and the IFD structure:

Code Select Expand


exiftool -v imagefilename.DNG

(type this into the terminal and replace 'imagefilename.DNG' with the actual name of your DNG you wish to inspect)

http://wwwimages.adobe.com/content/dam/Adobe/en/devnet/cinemadng/pdfs/CinemaDNG_Format_Specification_v1_1.pdf

[Pith]

Thank you, dmilligan!
Your posts are great source of information all over the forum.

Thank you again for fast and comprehensive reply. Everything's clear now.