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Resolution of JPEG previews in DNG files

Started Sep 29, 2021 | Discussions
dwynn New Member • Posts: 4
Resolution of JPEG previews in DNG files
1

My M6 Mark II photos are recorded as CR3 RAW files. When I convert these to DNG using Adobe's DNG Converter (ver. 13.4). Regardless of whether the Converter's Preferences > Preview/Fast Load Data > JPEG Preview: is set to "Medium Size" or to "Full Size", the JPEG preview in the resulting DNG file is always 1024 x 683. (I extract the previews using exiftool.) OTOH, the previews in the CR3 files are 1620 x 1080.

(1) Shouldn't changing the JPEG Preview size setting change the resolution of the preview in the resulting DNG file? (2) With the "Full Size" setting, should I expect the DNG and CR3 previews to have the same resolution?

Canon EOS M6 II
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PhilM oz Senior Member • Posts: 1,350
Re: Resolution of JPEG previews in DNG files
1

How are you extracting the images?

If you set the 'Full Size Preview' option in the DNG converter then you actually end up with 2 previews, the medium sized one and another full size JPEG image.

Using the command line you need to use a different option to extract the fill size JPEG preview.

'exiftool -b -PreviewImage' - this will always extract the medium size preview

'exittool -b JpgFromRaw' - this will extract the full size preview (only if DNG saved with this option)

OP dwynn New Member • Posts: 4
Re: Resolution of JPEG previews in DNG files

PhilM oz wrote:

How are you extracting the images?

If you set the 'Full Size Preview' option in the DNG converter then you actually end up with 2 previews, the medium sized one and another full size JPEG image.

Using the command line you need to use a different option to extract the fill size JPEG preview.

'exiftool -b -PreviewImage' - this will always extract the medium size preview

'exittool -b JpgFromRaw' - this will extract the full size preview (only if DNG saved with this option)

Thank you, Phil. Your information was just what I needed. I was unaware of the jpgFromRaw" option for exiftool.

cr3shooter Junior Member • Posts: 42
Re: Resolution of JPEG previews in DNG files

I’m using version 12.0.0.322 of the Adobe DNG converter. It’s some way off the latest but I’ve got no reason to upgrade when it works fine. Conversion works fine and the embedded Jpeg is 6984 x 4660.

Below is a screenshot of my preference settings in the converter.

An easy way to extract the Jpeg from a raw file is to use the free Faststone raw viewer, View the raw file (actually displaying the Jpeg preview) then right click and use the “Save As” option to save the Jpeg.

OP dwynn New Member • Posts: 4
Re: Resolution of JPEG previews in DNG files

cr2shooter wrote:

I’m using version 12.0.0.322 of the Adobe DNG converter. It’s some way off the latest but I’ve got no reason to upgrade when it works fine. Conversion works fine and the embedded Jpeg is 6984 x 4660.

Below is a screenshot of my preference settings in the converter.

An easy way to extract the Jpeg from a raw file is to use the free Faststone raw viewer, View the raw file (actually displaying the Jpeg preview) then right click and use the “Save As” option to save the Jpeg.

Thank you for the Faststone lead, cr2shooter. That certainly seems easier than my way of using exiftool.

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