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Using Magic Lantern => Raw Video => Raw Video Postprocessing => Topic started by: jdjakins on October 10, 2014, 08:45:02 AM

Title: 5d Mark III strange dng problem
Post by: jdjakins on October 10, 2014, 08:45:02 AM
To begin, thanks for reading.

The issue: I have a 4 min or so dng sequence. The DNGs, when viewed in Davinci or ACR, look terrible. As though the blacks and shadows have gone missing. In preview (on a mac), the images look normal, i.e. Detail is present in the shadows. Any ideas?

Is this too vague? I'll try to upload some images to illustrate.
Title: Re: 5d Mark III strange dng problem
Post by: jdjakins on October 10, 2014, 09:00:17 AM
Also, I thought I better mention, I used raw2dng to create the dngs. Can't remember the build I'm using on the Mark iii, but have never had any issue before.
Title: Re: 5d Mark III strange dng problem
Post by: dmilligan on October 10, 2014, 03:26:45 PM
Quote from: jdjakins on October 10, 2014, 08:45:02 AM
Is this too vague?
Yes
Title: Re: 5d Mark III strange dng problem
Post by: jdjakins on October 10, 2014, 07:09:08 PM
Thanks for the reply. Sorry It was a bit too late for me to upload examples last night. Below are two examples of the strange DNG behavior I'm experiencing. In both cases, they appear to be normal when previewed, but once opened in ACR or Davinci, the problems are present. I'm sorry I don't have a better vocabulary or understanding about what might be happening to make it a bit more clear. I've tried using both RAW2DNG and RawMagic. Both have same results. If you take a look at the following perhaps it will be more clear. Why would preview display them correctly? Does Preview Debayer? 

https://www.dropbox.com/s/0uo8jrfzwcwtk4v/M09-1903_C0000_00048.dng?dl=0
https://www.dropbox.com/s/g2ihlscad2ubo6u/M09-1904_C0000_00101.dng?dl=0
Title: Re: 5d Mark III strange dng problem
Post by: ayshih on October 10, 2014, 09:15:11 PM
I'm not able to look at the images right now, but this is almost certainly a problem with incorrect black levels in the EXIF information of the DNGs.  Unlike most applications, Preview ignores the EXIF black level and instead uses a default value for the particular camera model.  So, while Preview's behavior is generally undesirable, it can happen to skirt a problem when the black level in the file is wrong.

See http://www.magiclantern.fm/forum/index.php?topic=13473.msg130232#msg130232 for how to change the black level in the DNGs (you may need to use a value different from 2048 depending on your camera).
Title: Re: 5d Mark III strange dng problem
Post by: jdjakins on October 10, 2014, 09:47:45 PM
@ayshih THANK YOU! Exiftool solved the issue. Thanks for pointing me in the right direction! You are awesome.