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Print Page - How to access DNG Preview jpg?

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DAM Stuff => DNG => Topic started by: jeremyrh on March 15, 2006, 03:36:55 AM



Title: How to access DNG Preview jpg?
Post by: jeremyrh on March 15, 2006, 03:36:55 AM
I understand that a DNG file includes a JPG which reflects the colour adjustments made to the underlying RAW file. I can see that this would be useful to produce some quick prints etc (and that can be done via iVMP?). Suppose I want to do more than print - for example if I want to use that JPG as an item in a web gallery without the hassle of opening the RAW file, or mail the JPG to my mother etc etc etc - how do I access the JPG image in teh DNG file?

As an iVMP-specific question: suppose I wanted to make an html gallery using the JPG previews, not the RAW files - how would I do that?

I usually shoot NEF+JPG because it's handy to have a small version of the image to play with. If DNG will hold both versions I may be won over to the DNG camp  :D

Thanks for any pointers!!

Jeremy.


Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on March 15, 2006, 06:38:26 AM
Currently, you access that preview only with iView MediaPro and idImager.  If you use the convert image function, iView will access the preview rather than the RAW data.

You need to make sure you have your preferences set correctly.  Use Manufacturer rendering and click "use embedded preview".

You will find that this greatly unifies the workflow.

Interesting that you might have actually learned something from a book when you are telling the world:

>What is there in the book that you hadn't already figured out for yourself?
>So I suspect that not everyone agrees with me, but I found this book an utter waste of money. Anyone want to buy my copy:-) ??

Perhaps you are not as smart, or not as good a reader as you think you are. ;-)
Peter



Title: Re: How to access DNG Preview jpg?
Post by: jeremyrh on March 15, 2006, 07:06:24 AM
Currently, you access that preview only with iView MediaPro and idImager.  If you use the convert image function, iView will access the preview rather than the RAW data.

You need to make sure you have your preferences set correctly.  Use Manufacturer rendering and click "use embedded preview".

You will find that this greatly unifies the workflow.

Interesting that you might have actually learned something from a book when you are telling the world:

>What is there in the book that you hadn't already figured out for yourself?
>So I suspect that not everyone agrees with me, but I found this book an utter waste of money. Anyone want to buy my copy:-) ??

Perhaps you are not as smart, or not as good a reader as you think you are. ;-)
Peter


Maybe you're right, Peter - perhaps in the hundreds of pages there was a tidbit that I didn't already figure out.

I haven't mentioned your book here, because I prefer to focus on productive discussion, but for what it's worth, my opinion stands. I bought it on the basis of the comments I read in various forums, but if I'd seen it in a bookshop and seen how Adobe-centric it is, or what the discussion of other issues was like, I wouldn't have done so. Others mileage may vary.

Thanks, anyway, for the clarification.


Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on March 15, 2006, 07:27:09 AM
If you are going to use DNG, then you will be moving to an Adobe workflow, at least at the moment.  I hope that soon we will see other applications writing as well as reading DNGs. (Thoss that write at the momment do not include a full embedded preview.)
Peter


Title: Re: How to access DNG Preview jpg?
Post by: danaltick on March 15, 2006, 10:20:45 AM
I feel compelled to re-offer up my own review of the book again http://www.amazon.com/gp/cdp/member-reviews/A4FGHJCUG6PQ5/ref=cm_cr_auth/103-4654559-2351864?%5Fencoding=UTF8.

I'll let it speak for itself.

I will admit, there was quite a bit of information in the book that I did already know as a computer engineer; however, there was also a lot I didn't; and the book does not assume you are a computer engineer.  And more than that, the book put all the pieces together and documented it as a complete work....and that is something you just can't put a price tag on.

Dan


Title: Re: How to access DNG Preview jpg?
Post by: jeremyrh on March 15, 2006, 10:39:48 AM
If you are going to use DNG, then you will be moving to an Adobe workflow, at least at the moment.  I hope that soon we will see other applications writing as well as reading DNGs. (Thoss that write at the momment do not include a full embedded preview.)
Peter

Indeed, but if only iView will deal with the DNG large preview, then the incentive to change is not huge. I had wondered if perhaps there is a simple way to export the JPG preview untouched, without further loss, but IIUC, then you can't do that. As it is, you can use the NEF preview in iVMP, and as long as you don't want an image bigger than 1600px, you save myself the bother of converting a file.

If at some point there should appear a big range of utilities that use the big preview in a valuable way then you can re-think.


Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on March 15, 2006, 10:54:42 AM
iView and idImager are just the first to use the preview.  Expect this to be widespread functionality before the end of 2006. (Adobe even might get around to using it.)  It greatly streamlines the workflow, and lets multiple software render the image exactly as adjusted. It is not surprising that this is not widely supported yet, since it is such new functionality. My guess is that, prior to the publication of my book, only a handful of people  understood how this solves so many problems for photographers. And until December 11th, no one could even see this preview accurately.  As people start to understand how it works, it is being rapidly adopted by professionals.

Mismatch rendering is an inherent problem with RAW files, as is slow rendering from RAW data.  Those of us who have to make a living off digital photography need to speed up the workflow and get predictable results across platforms and applications.
Peter


Title: Re: How to access DNG Preview jpg?
Post by: jeremyrh on March 15, 2006, 11:31:29 AM
Those of us who have to make a living off digital photography need to speed up the workflow and get predictable results across platforms and applications.
Peter

And those of us who don't ... errr ... don't. 8)


Title: Re: How to access DNG Preview jpg?
Post by: johnbeardy on March 15, 2006, 11:42:47 AM
Portfolio 8 also makes use of large embedded previews. Now they're around, it's a no brainer to exploit them. But it's a curious argument indeed that serious photographers don't need to speed up the workflow and get predictable results across platforms and applications.


Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on March 15, 2006, 12:34:27 PM
John,
So Portfolio released an upgrade that will now access the full res of the preview?  As I recall, when 8 was first released, they claimed they would but did not, in fact, do it.
This would be good news.
Peter


Title: Re: How to access DNG Preview jpg?
Post by: johnbeardy on March 15, 2006, 01:06:43 PM
Peter

They haven't released an update since 8, in spite of there being some bugs in the program - fewer than iView but by comparison they made fewer steps forward and were more focussed on fixing old bugs. Anyway, I may have written somewhere that it didn't work as claimed. I then found that it would do so if a full size preview was in the file - my early tests had included DNG's without full size previews and I was more concerned about their resolving other issues such as rotation.

One nice feature is that once Portfolio extracts a preview file (equivalent to the new iView preview) then there are options to generate web pages or other output from those files rather than the potentially-offline originals.

John



Title: Re: How to access DNG Preview jpg?
Post by: jeremyrh on March 15, 2006, 02:27:10 PM
But it's a curious argument indeed that serious photographers don't need to speed up the workflow and get predictable results across platforms and applications.
Well, John, I was really just teasing, but the serious issue is that an "amateur" will not drop dead if the photos he promised for Friday actually get printed on Saturday, and he may prefer to economise on mouse clicks, on conversion processes, or indeed on software. That amateur has legitimate DAM needs and priorities that may not be served by the Adobe workflow.


Title: Re: How to access DNG Preview jpg?
Post by: Rick McCleary on March 15, 2006, 02:33:33 PM
One nice feature is that once Portfolio extracts a preview file (equivalent to the new iView preview) then there are options to generate web pages or other output from those files rather than the potentially-offline originals.

That is indeed a nice feature.  How is that accomplished?  Is the extraction of the preview file an automatic part of importing into Portfolio (or at least a preference), or is it on an a la carte basis?  I would imagine that your Portfolio file could get pretty large.


Title: Re: How to access DNG Preview jpg?
Post by: johnbeardy on March 15, 2006, 04:11:01 PM
It's a preference and works upon import. Portfolio has long had preview files and stores them as jpeg files separate to the catalogue. As a result, the Portfolio data file remains much smaller than an iView file with previews.


Title: Re: How to access DNG Preview jpg?
Post by: Joe Reifer on March 24, 2006, 01:20:56 PM
Being able to access a DNG preview jpg would allow huge time savings for part of my current workflow that is a big pain - Copyright registration.

My current workflow is to use Image Processor in Photoshop to convert my RAW images to 600 pixel jpegs for bulk copyright registration. For event shooting & other high volume work, this process is really time consuming.

If there was a way to quickly & easily extract the DNG jpeg preview & use that for Copyright registration I would be thrilled. Any other strategies for this onerous task are most welcome, too!  :)

Cheers,

Joe


Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on March 25, 2006, 01:50:27 PM
Joe,
Are you using an asset manager? (iView or Portfolio)
Peter


Title: Re: How to access DNG Preview jpg?
Post by: Joe Reifer on March 27, 2006, 04:42:29 PM
Hi Peter -

I am using iView Media Pro 2.64, and will be upgrading to 3.02 within the next week or two.
Is there a good way to pull the 640 pixel JPEGs out of iView? Maybe building a web gallery and just using the image files?

Thanks,

Joe


Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on March 27, 2006, 05:21:37 PM
Joe,
Although that was planned, it does not seem to be implemented yet.  So the media needs to be present for there to be a web gallery or some kind of converted image.

If you are using DNG, then extraction of the DNG preview is very fast.
Peter


Title: Re: How to access DNG Preview jpg?
Post by: Joe Reifer on March 28, 2006, 09:33:48 AM
Thanks Peter. I am in the process of converting to a DNG workflow - if the jpeg preview extraction speed is much faster than RAW, then that's another nice benefit for me.  ;D


Title: Re: How to access DNG Preview jpg?
Post by: Nick Rains on April 11, 2006, 03:19:22 AM
Though I have yet to check this is so, I believe the newest iteration of IMatch can also access DNG embedded previews. Certainly Mario Westphal was intending including this but I think the DNG support in the program is outsourced.

Maybe others can confirm this new feature...

I used to use IMatch, when IView was less advanced. However I now use IView3 and now find it more intuitive, if less powerful.




Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on April 11, 2006, 06:13:10 AM
Nick,
If you think iView is not powerful, you probably have not explored it thoroughly.  What is missing that you want?
Peter


Title: Re: How to access DNG Preview jpg?
Post by: Nick Rains on April 11, 2006, 03:54:35 PM
Peter

I don't mean that IView is not powerful, it most certainly is, it's just that IMatch is more powerful.

There so many more functions, options, scripts, templates in IMatch but I think that they tend to confuse the user. And the interface is super-cluttered as well. I found IMatch very easy to use at a low level and it generates thumbs pretty fast, but to use it 'seriously' is less easy than IView3.

I am very familiar with IView and for my money it has the right mix of power and useability.

Nick


Title: Re: How to access DNG Preview jpg?
Post by: jeremynicholl on April 28, 2006, 04:10:20 AM
Currently, you access that preview only with iView MediaPro and idImager.  If you use the convert image function, iView will access the preview rather than the RAW data.

You need to make sure you have your preferences set correctly.  Use Manufacturer rendering and click "use embedded preview".

You will find that this greatly unifies the workflow.


This is a nice idea but:

So far as I can see iView can't read DNG files' colour profile, and since it can't it converts the profile to sRGB by default. At least that seems to be what's happening here. Bridge shows my raw files and the DNG derivitives as Adobe RGB98, but when the same files are placed in iView I'm sold they are sRGB. That means when iView extracts the JPG preview it is also in sRGB, which isn't what I want to send as proofs. Of course, I can then convert these back to the correct space in Photoshop, but that's not much of a workflow.

Am I doing something wrong, or does iView really handle DNG files in this manner?

Jeremy Nicholl


Title: Re: How to access DNG Preview jpg?
Post by: gudbjargarson on April 28, 2006, 06:10:41 AM
Imatch 3.5 can display the jpg preview of the DNG.  I use it to show full size slideshows of the coverted files from Adobe Raw without problems.

Regards,
Johann
http://joephotos.net


Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on April 28, 2006, 08:41:06 AM
Jeremy,
A RAW file does not have a "profile" as we commonly know it.  When you select a profile in camera, you are just telling the camera:
1. What profile to create the JPEG in
2. If you use manufacturer's software, that instruction wil carry over to how that software will process the image.

The embedded preview in a DNG is sRGB, even though it s not tagged as such.  iView correctly converts this to a tagged derivative file when it uses the preview.

You should do some comparisons as to how proofs render in different color spaces.  I think you will be surprised.
Peter


Title: Re: How to access DNG Preview jpg?
Post by: jeremynicholl on April 28, 2006, 10:34:55 AM
Jeremy,
A RAW file does not have a "profile" as we commonly know it.  When you select a profile in camera, you are just telling the camera:
1. What profile to create the JPEG in
2. If you use manufacturer's software, that instruction wil carry over to how that software will process the image.

The embedded preview in a DNG is sRGB, even though it s not tagged as such.  iView correctly converts this to a tagged derivative file when it uses the preview.

You should do some comparisons as to how proofs render in different color spaces.  I think you will be surprised.
Peter


I'm sorry, I was a bit imprecise in my original post. I realise a RAW file has no profile as such. I always shoot RAW+JPG, simply because I might need to send an image immediately. 99% of the time the JPGs are junked, but they are profiled by the camera as RGB98.

What surprised me was the following. When I viewed the RAW files in Bridge they were tagged as RGB98 as I expected. When I converted the RAWs to DNG and viewed them in Bridge they were still tagged RGB98. But when I put the DNG files in iView and extracted the JPGs I found these were tagged sRGB. When I looked in the iView "Manage Colour Profiles" action I was told "The selected media item can't be colour managed. Only RGB, CMYK and Grayscale Photoshop, TIFF or JPEG images are supported."

That made me think that iView can't colour manage DNG files [presumably because they are in effect RAW files], but applies an sRGB profile to the extracted JPGs. I assumed iView was simply making a bad call. But you seem to be saying something different: namely that Adobe have decided to make the DNG embedded preview sRGB, but without tagging it as such. If so it seems a very odd decision for two reasons. Firstly to make it sRGB rather than, for example, RGB98: after all the latter is "Adobe's" colour space.  And secondly, not to tag it at all: whatever happened to colour management?

I used the term "proofs" very loosely. What I was hoping to do was solve a problem which sometimes appears - like today - when an editor suddenly says she woud like to see "what we've got so far" halfway through a shoot. I'd hoped that I could simply batch process the DNG files in Bridge's auto exposure, extract the Pretty Good Print JPGs, and send those. But just as some clients think "we need it at 300dpi", plenty will say "we need it in RGB98". If they suddenly receive images in a different space they get confused.

The obvious workaround is to convert the extracted JPGs to RGB98, but even with a script that's an extra step in the workflow, and one which would not be necessary if the extracted JPGs were in a more logical colour space.

Jeremy Nicholl



Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on April 28, 2006, 10:03:33 PM
Jeremy,
Try actually doing this in iView, and comparing it to the Adobe1998 results in ACR.  Again, I think you will be surprised at how small the difference is (depending on the image).

It's not an odd decision, considering that sRGB is more likely to be reproduced accurately if you are sending it out, and don't know for sure that the person receiving the file has any idea how to practice color management.  This is a very common situation.

Many more will be confused by Adobe1998 color space than by sRGB.

And if an editor is savvy enough to specify a color space, a well-corrected sRGB file will generally be a welcome relief to the unmanaged, oversharpened, clipped, and out of gamut crap they would typically see coming in.

That said, I do think it would be nice if you could specify the color space of the embedded preview.
Peter



Title: Re: How to access DNG Preview jpg?
Post by: jeremynicholl on May 02, 2006, 11:14:25 AM
Jeremy,
Try actually doing this in iView, and comparing it to the Adobe1998 results in ACR.  Again, I think you will be surprised at how small the difference is (depending on the image).

It's not an odd decision, considering that sRGB is more likely to be reproduced accurately if you are sending it out, and don't know for sure that the person receiving the file has any idea how to practice color management.  This is a very common situation.

Many more will be confused by Adobe1998 color space than by sRGB.

And if an editor is savvy enough to specify a color space, a well-corrected sRGB file will generally be a welcome relief to the unmanaged, oversharpened, clipped, and out of gamut crap they would typically see coming in.

That said, I do think it would be nice if you could specify the color space of the embedded preview.
Peter




Mmm, yes you're right, there's not much difference. And I'd forgotten about the "ignoramus on the other end" factor. Like you say, it would be nice to be able to specify the colour space but in practical terms it's probably not that important; I think maybe the sRGB surprise just made me grumpy.

Thanks for your help. And DAM good book by the way!

Jeremy Nicholl


Title: Re: How to access DNG Preview jpg?
Post by: David on April 15, 2007, 11:25:52 AM
My only problem right now is that I have some ORF files in my iView 3.1 catalogue and they now have a small preview so if I check the use embedded preview box in iView Media Rendering preferences I get this small preview in the image window as well as the catalogue window.

Now I am going to get my ORFs out of the catalogue anyway - but it bugs me. Did I put these previews in or are they standard in an ORF raw file.

Thanks

David


Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on April 22, 2007, 06:12:41 PM
David,
Sorry, I can't answer that.  Any proprietary Raw is specific to the camera.  You'll have to check with Olympus.
Peter


Title: Re: How to access DNG Preview jpg?
Post by: David on November 18, 2007, 01:40:25 PM
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


Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on November 18, 2007, 03:02:21 PM
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




Title: Re: How to access DNG Preview jpg?
Post by: David on November 18, 2007, 03:48:49 PM
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


Title: Re: How to access DNG Preview jpg?
Post by: peterkrogh on November 18, 2007, 08:45:20 PM
David,
Could be.
How did you enter the GPS data?
Peter


Title: Re: How to access DNG Preview jpg?
Post by: David on November 18, 2007, 09:14:40 PM
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


Title: Re: How to access DNG Preview jpg?
Post by: rogerhoward on September 05, 2008, 01:19:46 PM
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


Title: Re: How to access DNG Preview jpg?
Post by: David on September 13, 2008, 08:34:49 AM
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' \;



Title: Re: How to access DNG Preview jpg?
Post by: rogerhoward on September 13, 2008, 01:46:37 PM
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


Title: Re: How to access DNG Preview jpg?
Post by: David on September 13, 2008, 02:07:37 PM
Roger,

Mac Unix

Dave