Photoshop and DNG - saving as original

[Mike Rawcs]

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I'm using Photoshop CS3 to remove dust from my M9 DNG files (reasoning that I'm never going to want the dust spots so why not remove them permanently?). When I open the files the Open dialogue box shows "Enable all readable documents" and the format box shows "Photoshop Raw"

 

Next I'm taken to a Camera Raw preview and then into Photoshop. After cloning out the dust spot (only one so-far) I attempt to save but get the message "Save as "file number.psd".

 

I want to save the file in its original DNG format and I can change the psd suffix to DNG and receive the message "An item with named (file name.DNG) already exists in this location. Do you want to replace it with the one you are saving?" If I click OK the file is saved but if I open it again and make another change and save it I get no messages.

 

Obviously Photoshop is doing something to the original DNG other that just saving the adjustment but I don't know what. Can anyone please help?

 

Can someone also explain what a psd file is? What are the advantages / disadvantages of saving as psd?

 

Many thanks,

 

Mike.

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[andybarton]

A psd file is a native photoshop file.

 

It sounds like you are trying to save the file in the same location as the original. Never a good idea.

 

Further, IIRC, Photoshop will not Save As a DNG.

[Mike Rawcs]

Thanks for the reply, Andy.

IIRC?

I thought that DNG was a format developed by Adobe? If this is the case it seems strange that Photoshop doesn't support it: especially as Lightroom allows the user to convert non-DNG to DNG on import.

I hear you about saving saving a file to the same location: I'm obviously attempting to keep things simple and not have files all over the place. It has crossed my mind as to how a file can be saved and deleted at the same time but I presumed that if it was of the same format it would be amended rather than deleted. But I presumed, didn't I?

 

Thanks again,

 

Mike.

[ho_co]

Mike, just changing the extension to DNG doesn't change the file to DNG.

 

It sounds as if you're overwriting your original file with a modified copy; your output is likely a PSD file, which you're then renaming to pretend it's a DNG.

 

IIRC, Photoshop CS3 doesn't support the newest version of the DNG specification, but the M's don't write in the newest standard either.

 

As Jaap said, it's never good to lose the original. The reason is that you might want to make other changes later, or to process it differently--and you no longer have the original to go back to.

 

That's one of the reasons that Photoshop by default stores a new version of the image in the Photoshop format, rather than replacing the original. Once you've saved a modified (non-raw) file, you can save over it (rewrite it) as often as you want.

 

Think of the DNG as a negative. (DNG = "digital negative") If you replace it with a modified file of a different type, it's like throwing away the negative and just saving a print of it.

[ho_co]

... I thought that DNG was a format developed by Adobe? If this is the case it seems strange that Photoshop doesn't support it: especially as Lightroom allows the user to convert non-DNG to DNG on import....

Mike, Photoshop does support DNG. That's how it read the file to start with.

 

Since you mention Lightroom, it automatically saves a modified DNG with your change saved non-destructively in the file. With Photoshop's filesaving, all changes are permanent. That is, Photoshop's modifications are at the bit level, while Lightroom modifies only the recipe for correcting the file.

 

 

BTW, just as in Lightroom, from ACR within CS4 (and IIRC in CS3), you can use the "Save" button to save the original file as a DNG. The Adobe DNG file is smaller than the Leica original because ACR converts the file to a version without the look-up-table.

 

But in Photoshop you can't save a modified file as DNG, because you've already modified some of the data.

 

Lightroom is different in that it saves not the modified data, but the instructions of how to modify the data next time the file is opened. The instructions apply only to Lightroom, of course, so they won't be interpreted in Photoshop or Capture One or whatever else.

[hoppyman]

BTW, just as in Lightroom, from ACR within CS4 (and IIRC in CS3), you can use the "Save" button to save the original file as a DNG. The Adobe DNG file is smaller than the Leica original because ACR converts the file to a version without the look-up-table.

.......................

 

That is confusing two different compression methods though. Always with the M8 and optionally with the M9 the camera makes the DNG smaller by using some voodoo to store almost all of the (originally 14 bit) information in the original as an 8 bit file. Then it gets 're-inflated' when processed outside the camera.

With all DNGs, (those stored that way AND those stored uncompressed) Adobe Camera Raw and Lightroom will apply additional LOSSLESS compression on import. In this case just more efficient processing with no data loss whatsoever.

In both Camera Raw (which is part of Photoshop of course) and Lightroom, edit instructions are stored in a special part of the DNG file but the actual data is unchanged.

However both Camera Raw and Lightroom can also make NEW DNG files from other formats, including from JPG's, TIFF's and PSD's as well as existing DNG's. In those cases of course there is no new information added and a DNG made from a lower quality image (for example from a low resolution JPG) is not the same thing as shooting a Raw original.

..........................................................

But in Photoshop you can't save a modified file as DNG, because you've already modified some of the data.

Lightroom is different in that it saves not the modified data, but the instructions of how to modify the data next time the file is opened. The instructions apply only to Lightroom, of course, so they won't be interpreted in Photoshop or Capture One or whatever else.

........................................................

Providing the later versions of Camera Raw and Capture One are used, they can read Lightroom edited DNG files with no problems. If you open a DNG edited in the latest version of Lightroom in an earlier version of Camera Raw, only edits that have no corresponding tools in the older program do not display.

The Raw processing engine in Camera Raw is identical to that of the same version Lightroom. (Currently Camera Raw 6.41 and Lightroom 3.41)

[ho_co]

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... Providing the later versions of Camera Raw and Capture One are used, they can read Lightroom edited DNG files with no problems. If you open a DNG edited in the latest version of Lightroom in an earlier version of Camera Raw, only edits that have no corresponding tools in the older program do not display....

Thanks for the correction, Geoff. But then in both cases (PS CS5 and C1), the files are actually modified, right? That is, using CS5 and C1 will take you out of the non-destructive editing that Lightroom does and won't store the file again as a DNG--and we're back where we started.

 

On the matter of compression, I stand by what I said. M8 and (optionally) M9 incorporate a very simple, slightly lossy compression algorithm, but that is wholly different from the lossless compression applied by DNG converter, ACR and Lightroom.

 

Take an M8 file and run it through Adobe's DNG conversion, and it will be half the size of the original file with no loss of data.

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There's no confusion between the two compression processes.

 

And FWIW, I think it's wrong to characterize the M8/M9's compression as "some kind of voodoo." All that's happening is that with the look-up table, the camera stores in each pixel a pointer to one of 255 bins, in each of which a number between 1 and 65535 is stored. Not voodoo.

 

As I read the OP's question, it's about overwriting a DNG with a PSD. The M cameras' DNG compression scheme is another topic altogether.

[ho_co]

... both Camera Raw and Lightroom can also make NEW DNG files from other formats, including from JPG's, TIFF's and PSD's

 

Now that's a new one to me. How do I open a JPG in Camera Raw in order to save it as DNG? (I'm still using PS CS4; maybe that's a function added in PS CS5?)

 

As I said above, it seems crazy to me to enable a user to make hobbled DNGs. That defeats the whole purpose of the digital negative format.

[Mike Rawcs]

Thanks for the replies everyone, I thought that I would be able to save an amended DNG file as a DNG file in Photoshop but such is not the case. I do understand the concept of the digital negative: more so now.

 

From now on I'll just remove any dust found on a photograph with either Lightroom or Aperture and leave my DNGs alone!

 

Thanks again for your help.

 

Mike,

[hoppyman]

Howard, on 'voodoo' that was simply an attempt to make a lighter, non-technical remark.

If you open a DNG that has been edited in one app in another, you are not modifying it. You possibly may not see every instruction rendered in the preview but the original data (image) is unchanged. If you save a copy as another format (PSD, TIFF, JPG and edit that , yes this is potentially destructive of course. However Lightroom always saves edits of even those non-Raw formats as instructions and again the original image is unchanged.

If you preview say a JPG in Bridge, you can elect to edit with the Camera Raw tools (right click, open in Camera Raw) for the same situation.

 

Back to opening a TIFF or whatever in Photoshop (I have CS5) of course all of the existing options are still there if you edit on layers etc naturally.

 

On M8 compression etc, it sounds like we are saying the same thing, no disagreement

On making DNG versions from other format, remember that I said that you do not gain any quality by doing so, only that it can be done. One possible useful function of making a new DNG from an existing DNG (say after developing/cropping) is that the new version can be smaller or prevent reverse processing back to the original if you wanted.

 

 

I'm a big fan of DNG for a number of reasons. Any number of threads could be developed from that!

[mjh]

On making DNG versions from other format, remember that I said that you do not gain any quality by doing so, only that it can be done.

But how? Apart from the fact that the very concept of saving an image in DNG format doesn’t make sense to me (converting a ‘developed’ RGB image back into raw data is like restoring virginity), I wouldn’t know how one would go about even attempting it.

[hoppyman]

Hi Michael. Well I was just discussing functionality rather than making a recommendation. A DNG is only a variation of the TIFF standard as I understand it anyway.

You cannot of course get back anything discarded prior to saving a new version as a DNG, but you can then be working from that point with all of the advantages of Raw though.

 

For the technically curious:

In Lightroom 3, open a JPG in Library module, select export and in the file settings choose DNG as your desired format. Since the DNG is self-contained all of the edit info is available should you open the file then in another app, as opposed just being in the catalog. Naturally ACR and LR talk perfectly with each other on the same machine anyway, providing versions are equal.

 

That is different to right clicking to 'open in Camera Raw' for a JPG. (to use the Raw tools) In that instance the edits are saved as separate instructions (Sidecar file I guess) and Camera Raw then becomes the default when you open that JPG again next time.

 

A bit amazed that I surprised YOU though I look to your posts as extremely knowledgeable and informative all of the time.

[sandymc]

But how? Apart from the fact that the very concept of saving an image in DNG format doesn’t make sense to me (converting a ‘developed’ RGB image back into raw data is like restoring virginity), I wouldn’t know how one would go about even attempting it.

 

It can make sense from a workflow/DAM perspective - as Geoff points out, DNG's allow all adjustments to be stored inside the DNG itself, so having a workflow where everything is DNG has its attractions.

 

Not that I'm inclined to go that route myself, but I can understand why some people do.

 

Sandy

[k-hawinkler]

It can make sense from a workflow/DAM perspective - as Geoff points out, DNG's allow all adjustments to be stored inside the DNG itself, so having a workflow where everything is DNG has its attractions.

 

Not that I'm inclined to go that route myself, but I can understand why some people do.

 

Sandy

 

 

If you do that, can you always go back to the original DNG?

 

Thanks, K-H.

[jaapv]

Thanks for the replies everyone, I thought that I would be able to save an amended DNG file as a DNG file in Photoshop but such is not the case. I do understand the concept of the digital negative: more so now.

 

From now on I'll just remove any dust found on a photograph with either Lightroom or Aperture and leave my DNGs alone!

 

Thanks again for your help.

 

Mike,

 

This only goes wrong if you try and save the file to the same folder. If you use "save as" you can save the file as anything you like to another folder without overwriting the original file.

If you want to compress your original file to the new DNG which is lossless you must use the DNG converter which you can download for free from Adobe. That little program will store any file as a DNG. Very practical if you get a raw file that is not supported by CS.

It is not specific photoshop. Your computer will always overwrite a file with exactly the same name as the new file if you save that new file to the same location.

[mjh]

If you do that, can you always go back to the original DNG?

The original data isn’t actually touched. The DNG out of camera contains the raw image data and the EXIF meta data, and none of these are touched. All the raw converter does is to store a description of the conversion parameters within the original file – it’s just another level of meta data that could alternatively be stored in a side-car file. Since this only adds to the file without modifying its original contents, the original data isn’t lost even when the file is modified.

 

But that’s not what the TO was about. After the raw converter (ACR in this case) has done its work and the converted image is imported into Photoshop for further modifications, there is no way to convert the full RGB image back into raw data. That would be quite different from storing conversion parameters in the DNG file.

[Mike Rawcs]

Thanks Jaapv, very interesting. I won't be doing what I did here again!

 

Mike.

[mjh]

A DNG is only a variation of the TIFF standard as I understand it anyway.

As is any raw file format that I am aware of. I don’t think that’s relevant within this context, though.

 

In Lightroom 3, open a JPG in Library module, select export and in the file settings choose DNG as your desired format. Since the DNG is self-contained all of the edit info is available should you open the file then in another app, as opposed just being in the catalog. Naturally ACR and LR talk perfectly with each other on the same machine anyway, providing versions are equal.

In that case it is still basically a JPEG file plus processing instructions; that is the DNG created this way isn’t a raw file. As long as you stay within the Adobe world this might be useful. Other raw converters wouldn’t know how to deal with it even when they support other types of DNG – they expect raw, not JPEG data.

 

The reason why Lightroom allows to save a JPEG this way is that Lightroom is strictly non-destructive. An edited image can be stored as the original image file plus processing instructions and can be recreated from these components. But while Photoshop offers many non-destructive tools by now (and Adobe’s developers would love to throw out all the old destructive tools if it weren’t for the customers demanding to keep those), at its core it is still basically a destructive image editing application.

 

So back to the original question: After importing a raw DNG file into Photoshop for image processing, can you save the result as a DNG again? No, you cannot. Theoretically it would be possible to turn Photoshop into a strictly non-destructive image editor; then you could take the original raw data in the DNG, add the conversion parameters chosen in ACR and the list of image editing operations applied within Photoshop, and save it all as a DNG that would still contain the raw data, but augmented with processing instructions. But for the time being this isn’t possible.

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[hoppyman]

Thank you Michael. I was responding to Howard's (Ho Co) post rather than the Original Poster. Perhaps I muddied the thread waters.

 

I just did the experiment and Lightroom 3.41 and Camera Raw 6.41 do indeed recognise and work with each other's DNG made from a JPG. My very seldom used Capture One 4.8.3 does not.

[sandymc]

To clarify the technicalities a bit, DNG images come in two "flavors"

 

1. CFA
   
2. Linear Raw
   

 

This is set by the PhotometricInterpretation tag in the DNG. CFA DNGs are your "normal" raw images, with Bayer or Foveron sensor data in them, such as produced by the M8 or M9. Linear raw DNGs are processed images - images that have been demosaiced, and typically had some other processing done to them.

 

What LR and Photoshop will write when you ask for a image that is already demosaiced to be written as DNG is the linear raw form. Likewise, toDNG (one of my apps), which can convert pretty much an bitmap image to DNG also writes linear raw DNGs.

 

However, if LR started with CFA (mosaiced) data, it keeps the CFA data, but adds instructions for postprocessing in the metadata.

 

Unfortunately, quite a lot of image processing software packages (e.g., C1) have incomplete DNG implementations, and will not read linear raw DNGs - or indeed some CFA DNGs.

 

Sandy