DNG Files

[Beyder28]

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Ok, sorry once again for another newb question. I have learned the basics of shooting Raw and its advantages. I know that DNG files contain more info and give you more freedom to work with in PP. I just dont understand why is it that when I shoot with DNG+Jpeg, the DNG file seems a bit brighter and is heavy on the saturation? All Im doing is importing both files from my SD card right into Aperture on my iMac.

[Tomcollins]

Hi,

Dng files are completely unprocessed files (like the negative of the film days) as opposed to the relatively high processed .jpg image. The in camera computer is adding colors, saturation, sharpness, contrast and other fixes to the .jpg file while it does noting to the DNG (raw) file. Although I have heard that even though the data in a raw file is untouched, that may not be entirely true, a little adjustment is being made...so I've heard.

It makes sense to me that your DNG file appears a little brighter (it hasn't had any in-camera processing) but I can't quite understand why the colors appear to be more saturated. Maybe someone else can help with that one.

Tom

[pico]

Hi,

Dng files are completely unprocessed files (like the negative of the film days) as opposed to the relatively high processed .jpg image. \

 

Untrue. Every vendor tweaks their DNG or raw files.

[Tomcollins]

I think that's what I said, that I've heard even raw files are adjusted, but I didn't know for sure.

[k-hawinkler]

Untrue. Every vendor tweaks their DNG or raw files.

 

 

References, say for Leica, Canon, Nikon, ... would be a good thing to have to support that statement.

 

Thanks, K-H.

[jaapv]

They have to do an amazing amount of processing - no raw converter would be able to read direct sensor output. On a CMos sensor on-sensor circuitry will balance pixel output to get rid of part of the noise, both CCD and CMos signals off-sensor will have to be amplified to reach the ISO rating, digital conversion will take place, corrections for vignetting and color shift and further noise reduction (very little of the last on Leica,) an embedded JPG preview must be generated and the DNG format must be written and EXIF added. I'm sure experts on this forum will point out a number of manipulations I have forgotten.

 

The phenomen from the OP is , I think, the original DNG preview JPG being adjusted to the parameters of the final out-of-camera JPG, which obviously does not apply to a DNG only output.

[Tomcollins]

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I think the bottom line here to answer the original question isn't whether or not DNG/RAW files are processed in camera or not (they are to a certain degree), but that they offer the photographer, in post processing, more information to work with than a .jpg file. But I still don't know why the original posters DNG's are showing more saturation than his .jpgs.

Tom

[jaapv]

A DNG as such shows nothing but the embedded jpg preview. A processed DNG file which is what the OP probably refers to shows the result of the conversion by the raw conversion program (ACR,LR,C1, Bibble, etc.) which allows the user to influence the color settings, including saturation. What he is seeing is his own preset.

[Tomcollins]

Thanks. That makes sense that the program they are using has a preset that's determining a change to the saturation on import. I hope the OP is following so they can take a look at how he has his presets set.

Tom

[ho_co]

References, say for Leica, Canon, Nikon, ... would be a good thing to have to support that statement....

 

On my D200, some of the color choices are still enabled when shooting NEF. I so seldom shoot it that I'd have to check to see which ones. I was surprised when the Nikon rep told me that these settings aren't shut out when I choose to shoot raw.

 

It's good that you ask for references, K-H, but I know this is one that is generally accepted. I was greatly surprised to hear that "raw" wasn't actually just a sensor-dump, even on the M8, but a couple forum members jumped in to convince me that a fair amount of processing goes on in-camera, and that the amount of processing varies among the brands.

[Beyder28]

I just feel like if I liked the extra saturation, in many cases, the raw file would be good to go without any PP. That's got to be wrong. Right?

[ho_co]

There's no requirement that you post-process.

 

In fact, I also find that my M8 files require much less PP than my Nikon files.

 

If you like what you're getting, so be it. You're the judge.

[wlaidlaw]

I thought the point of a DNG is that it was in effect a "read only file" and the equivalent of an original silver negative, with any alterations in a side-car file (.xml). This answered the arguments that any digital file was subject to manipulation and that there was no absolute truth in an image any more. However the hackers never stay still and I understand that DNG files can now be hacked and changed, thereby negating the original concept. If this is true, it rather sad.

 

Wilson

[tele_player]

Changing a DNG file isn't hacking.

 

The point of DNG has nothing to do with files being read-only.

Technically, there is no such thing as a read-only file. The read-only bit on a file is more of a suggestion to the OS to make it more difficult to change the file's contents.

 

The rationale for DNG is here:

Extend | Adobe Photoshop CS5

 

-Robert

 

I thought the point of a DNG is that it was in effect a "read only file" and the equivalent of an original silver negative, with any alterations in a side-car file (.xml). This answered the arguments that any digital file was subject to manipulation and that there was no absolute truth in an image any more. However the hackers never stay still and I understand that DNG files can now be hacked and changed, thereby negating the original concept. If this is true, it rather sad.

 

Wilson

[hoppyman]

Wilson there is some confusion there. Firstly a DNG, unlike other Raw formats does not store any edit information in a separate side-car file. It is written within a particular area of the DNG.

However it is important to note that information is still only a set of instructions and the actual data (after processing) as recorded by the camera is unaltered.

Most importantly of course you end up with 14 bit data instead of the 8 bit JPGs.

 

In camera the Raw information is certainly corrected and processed in various ways and the M9 for example needs to make significant adjustments just to produce a homogenous file at all. Altering those necessary corrections further is the basis of the forthcoming firmware too.

 

In fact there are parts of the current DNG standard (Opcodes) which provide for some additional corrections (distortion and chromatic aberration I think) to be recorded and optionally re-edited after the fact. Leica Camera does not implement those currently and arguably does not need too. The corrections for vignetting for example are baked-in. I don't know of any camera that does use those new features with DNG right now.

Those extra M9 corrections are additional to everything else that must be done to Raw files to produce a readable image at all.

 

M8 or M9 DNG previews whether embedded or written as higher quality versions in the Raw converter will certainly look different than JPGs written by the camera. Remember that you can't actually look at a DNG itself and see a 'normal' image. The default Camera Raw or Lightroom settings will also produce a JPG version that may look different too. In-camera JPGs are typically higher contrast and more saturated, that is more appealing to the eye which is exactly why they are adjusted that way.

Much better to have all of the information and then make a version with the JPG alterations that YOU want than have the camera make those decisions and discard so much information in the process.

[wlaidlaw]

Robert/Geoff,

 

Firstly of course I was in error about the separate sidecar file for DNG and as you say, alteration data is kept within a compartment inside the file.

 

I went to an Adobe Seminar in I think October 2004, where they were explaining the rationale behind the DNG format. One of the points they made was that they had worked with the US Library of Congress to come up with a format that could be recognised as "archival", where alterations would always be detectable and traceable. This was the point that I was trying to make, in that I have been told (whether it is true or not I cannot say) that now certain software has now been written which can make undetectable/untraceable alterations to the DNG image RAW/Pixel data, so that photographs can lie and it cannot be detected.

 

Wilson

[ho_co]

Wilson, there's also at least one piece of software on the market that professes to be able to recognize changes to the original image as shot.

 

See John Giordano's thread http://www.l-camera-forum.com/leica-forum/barnacks-bar/182121-white-house-photoshopping-analysed.html, though whether that has to do with DNGs or raws or anything else except general tonal gradients, I have no idea.