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lotech · 11-19-2023, 06:50 PM

I set my K3-1 to write DNG to a Flashair wireless SD on slot one, and to keep a JPG backup on the 2nd card. After long time of use the wireless SD started to fail, I received some corrupted images, when I download to the tablet I can see the preview, but when I edit with Snapseed it shows me corrupted image. I don't know if the preview is JPG or a special version of DNG, but how do I get that preview from the DNG ? I know Snapseed is not the best RAW processor, but that good enough for my kind of shooting. Btw is there any standard profile for DNG conversion to JPG, or how does the preview come up ?

**tduell** · 11-19-2023, 06:58 PM - **3 Likes**

Use dcraw to extract the embedded thumbnail image, if that is what you are saying you need.
The command line to do that would be ...

dcraw -e fred.DNG

assuming fred.DNG is the subject DNG filename.
Invoking dcraw without any arguments will display the full usage of dcraw.

Cheers,
Terry

lotech · 11-19-2023, 07:31 PM

Originally posted by tduell

Use dcraw to extract the embedded thumbnail image, if that is what you are saying you need.
The command line to do that would be ...

dcraw -e fred.DNG

assuming fred.DNG is the subject DNG filename.
Invoking dcraw without any arguments will display the full usage of dcraw.

Cheers,
Terry

Yeah that worked thanks !

**BigMackCam** · 11-19-2023, 10:11 PM - **1 Like**

Originally posted by lotech

I don't know if the preview is JPG or a special version of DNG

FYI, the preview is an embedded JPEG, and - if I remember correctly - limited in resolution and quality. You'd be better off using the backup JPEG on your slot 2 card

**seventhdr** · 11-20-2023, 02:13 AM - **1 Like**

Originally posted by BigMackCam

FYI, the preview is an embedded JPEG, and - if I remember correctly - limited in resolution and quality. You'd be better off using the backup JPEG on your slot 2 card

I seem to recall that the embedded JPG is a medium resolution file. Not sure about the quality level though.

Chris

lotech · 11-20-2023, 02:25 AM

Originally posted by BigMackCam

FYI, the preview is an embedded JPEG, and - if I remember correctly - limited in resolution and quality. You'd be better off using the backup JPEG on your slot 2 card

Yeah sure, thanks !

11-19-2023, 06:50 PM	#1
lotech Pentaxian Join Date: Apr 2012 Posts: 1,216	How do extract preview from a corrupted DNG file ? I set my K3-1 to write DNG to a Flashair wireless SD on slot one, and to keep a JPG backup on the 2nd card. After long time of use the wireless SD started to fail, I received some corrupted images, when I download to the tablet I can see the preview, but when I edit with Snapseed it shows me corrupted image. I don't know if the preview is JPG or a special version of DNG, but how do I get that preview from the DNG ? I know Snapseed is not the best RAW processor, but that good enough for my kind of shooting. Btw is there any standard profile for DNG conversion to JPG, or how does the preview come up ?

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11-19-2023, 06:58 PM - 3 Likes	#2
tduell Loyal Site Supporter Join Date: May 2015 Location: Melbourne Posts: 1,468	Use dcraw to extract the embedded thumbnail image, if that is what you are saying you need. The command line to do that would be ... dcraw -e fred.DNG assuming fred.DNG is the subject DNG filename. Invoking dcraw without any arguments will display the full usage of dcraw. Cheers, Terry

11-19-2023, 07:31 PM	#3
lotech Pentaxian Join Date: Apr 2012 Posts: 1,216 Original Poster	Originally posted by tduell Use dcraw to extract the embedded thumbnail image, if that is what you are saying you need. The command line to do that would be ... dcraw -e fred.DNG assuming fred.DNG is the subject DNG filename. Invoking dcraw without any arguments will display the full usage of dcraw. Cheers, Terry Yeah that worked thanks !

11-19-2023, 10:11 PM - 1 Like	#4
BigMackCam Digitiser of Films Join Date: Mar 2010 Location: North East of England Posts: 19,898	Originally posted by lotech I don't know if the preview is JPG or a special version of DNG FYI, the preview is an embedded JPEG, and - if I remember correctly - limited in resolution and quality. You'd be better off using the backup JPEG on your slot 2 card

11-20-2023, 02:13 AM - 1 Like	#5
seventhdr Site Supporter Join Date: Mar 2007 Location: Christchurch, New Zealand Photos: Gallery Posts: 1,361	Originally posted by BigMackCam FYI, the preview is an embedded JPEG, and - if I remember correctly - limited in resolution and quality. You'd be better off using the backup JPEG on your slot 2 card I seem to recall that the embedded JPG is a medium resolution file. Not sure about the quality level though. Chris

11-20-2023, 02:25 AM	#6
lotech Pentaxian Join Date: Apr 2012 Posts: 1,216 Original Poster	Originally posted by BigMackCam FYI, the preview is an embedded JPEG, and - if I remember correctly - limited in resolution and quality. You'd be better off using the backup JPEG on your slot 2 card Yeah sure, thanks !

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How do extract preview from a corrupted DNG file ?

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