How to access DNG Preview jpg?

[David Mackie]

Peter or anyone

I am using iView 3.1.3 to extract JPEGs from my DNGs but unfortunately even though I check the preserve EXIF/GPS option the EXIF data is not properly converted. It does not convert GPS lat, long, elevation nor the camera model and make. If I use ACR CS3 to convert to JPEG then all the EXIF data is properly stored in the JPEG.

Any thoughts?

David

[peterkrogh]

David,
I have not tested, but it would not surprise me to learn that variations in EXIF implementation between various camera and software manufacturers result in the loss of some of that data as files get passed aroud and converted.  If you're up for tracking it down with EXIFtool or some other software, you might be able to find out where things get dropped. 
If it's an Adobe problem, then they will likely be willing to make a fix. 
If it's iView, then the fix would only show up in Expression. 
And if it's the camera, then all bets are off...

Peter

[David Mackie]

Peter

Thanks. I don't think it is the camera as the GPS data is embedded after in standard fields. the camera make and model is not transferred. I will try with my C8080 Olympus...to see if some of the EXIF data is camera dependent.

I suspect it is iView myself...but a test with my other camera will help..

David

[peterkrogh]

David,
Could be.
How did you enter the GPS data?
Peter

[David Mackie]

Peter

I used GPSPhotoLinker. From Photoshop it looks like it is in the right headers and shows up in the right headers in iView.

David

[rogerhoward]

Hi guys, old thread I know, but since the threads stick around I'm starting to add my 2c where I think it's still useful.

I have a DNG-based workflow, opting for fullsize JPEG previews, which I update when my processing is complete. Since I have a huge library of DNG, generating Web renditions by batch processing in ACR or LR is way way toooo slow. Since I'm using DNG and embedded JPEG previews, the answer is easy (if you're at all handy with scripting - if encouraged enough I could provide an app to do this).

requires only exiftool (for the preview extraction) - I also use ImageMagick for generating the smaller versions.

exiftool -b -JpgFromRaw myimage.dng > output_previewpath.jpg

The syntax is different for images with smaller previews, btw.

So, for instance, here's a simple command which will work on OSX with exiftool properly installed, to extract previews for every file in a given path, placing the previews in the same path as the original, with ".jpg" appended to the original filename:

find "/path/to/image/directory" -name "*.dng" -exec exiftool -b -JpgFromRaw '{}' > '{}.jpg' \;

It's possible to copy the exif metadata from the original to the output JPEG at the same time; I use a similar command along with imagemagick to generate thumbnails and screen-size previews; the extraction part is about as fast as it could be, image conversions of course slow it down a little.

- Roger

[David Mackie]

Hi Roger

I am having trouble getting the -exec to work - it does not recognize the {} after the > redirection so I get one file called {}.jpg out

David

So, for instance, here's a simple command which will work on OSX with exiftool properly installed, to extract previews for every file in a given path, placing the previews in the same path as the original, with ".jpg" appended to the original filename:

find "/path/to/image/directory" -name "*.dng" -exec exiftool -b -JpgFromRaw '{}' > '{}.jpg' \;

[rogerhoward]

Are you on Windows using a DOS prompt, or using a unix-style toolset? I believe there's a find command in DOS that has different options than the find in unix-y environments... I'm not much of a DOS lover, so I always install cygwin on Windows (right after installing Firefox) so I can use a unix-like environment on Windows. Anyways, I digress. If you're using the Windows "find" command, I'm not familiar with it... the {} is just a placeholder variable for the path of the found file, if you're on Windows I'm sure the Windows find command has something similar. Or just install cygwin and the command should work as-is (I tested that before posting it from a Windows machine running cygwin).

-Roger

[David Mackie]

Roger,

Mac Unix

Dave