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Author Topic: Why are DxO DNG files so large?  (Read 14926 times)

JDClements

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Why are DxO DNG files so large?
« on: February 01, 2009, 10:16:59 am »

I just started playing with DxO, and am seeing huge DNG files being produced. For example, I feed in a 30meg CR2 file, and I get an 82meg DNG file out the other end. Why is that? If I convert the same file inside Lightroom, I get a 28meg DNG file.
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digitaldog

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Why are DxO DNG files so large?
« Reply #1 on: February 01, 2009, 10:56:00 am »

Quote from: JDClements
I just started playing with DxO, and am seeing huge DNG files being produced. For example, I feed in a 30meg CR2 file, and I get an 82meg DNG file out the other end. Why is that? If I convert the same file inside Lightroom, I get a 28meg DNG file.

I think (and could be wrong), its because there's a big fat rendered data file in there, not a Raw (or might be Raw + rendered file).

A DNG isn't necessarily containing a non rendered, non demosic'ed data.
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JDClements

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Why are DxO DNG files so large?
« Reply #2 on: February 01, 2009, 11:27:04 am »

I just tried a test. I took a CR2 file into DxO and did some visible alterations, especially to the white balance and tint. When I take the resulting (huge) DNG file  into LR, my changes show up. The image looks exactly like I had it in DxO. Except, the WB and tint numbers on the LR sliders are NOT what they were set at in DxO. The LR dropdown says "As Shot".

Now, I look at the original CR2 file that I brought into LR, and the "as shot" WB and tint are different again.
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francois

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Why are DxO DNG files so large?
« Reply #3 on: February 01, 2009, 11:33:58 am »

Quote from: JDClements
I just tried a test. I took a CR2 file into DxO and did some visible alterations, especially to the white balance and tint. When I take the resulting (huge) DNG file  into LR, my changes show up. The image looks exactly like I had it in DxO. Except, the WB and tint numbers on the LR sliders are NOT what they were set at in DxO. The LR dropdown says "As Shot".

Now, I look at the original CR2 file that I brought into LR, and the "as shot" WB and tint are different again.
I could well be wrong but I guess that DxO generates a new DNG file with R,G and B components. This could explain the ~3x big size than the original CR2 file.
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Francois

Panopeeper

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Why are DxO DNG files so large?
« Reply #4 on: February 01, 2009, 11:42:39 am »

If you start this program and "process" the file, it creates a chart of the file structure, called filename.taglist.txt. Upload that file, it shows what is there, how large, which format. etc.

It is a Windows program, but it works under Windows simulators on Mac. I have not tested it on Vista.
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Gabor

JDClements

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Why are DxO DNG files so large?
« Reply #5 on: February 01, 2009, 02:40:40 pm »

Quote from: Panopeeper
If you start this program and "process" the file, it creates a chart of the file structure, called filename.taglist.txt. Upload that file, it shows what is there, how large, which format. etc.

It is a Windows program, but it works under Windows simulators on Mac. I have not tested it on Vista.

The program worked on Vista for the CR2 file (except that it closes itself with no message after running a file). But it does not recognize DxO's DNG file: "The image file specification is incomplete or unsupported"
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JDClements

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Why are DxO DNG files so large?
« Reply #6 on: February 01, 2009, 02:48:03 pm »

Quote from: digitaldog
I think (and could be wrong), its because there's a big fat rendered data file in there, not a Raw (or might be Raw + rendered file).

A DNG isn't necessarily containing a non rendered, non demosic'ed data.

I am still finding the whole concept a little confusing, but this is what I think I understand:

> If LR takes a CR2 (or other) RAW file, and converts it to DNG, then it is still a RAW file, but in a different format. LR does the RAW conversion on the fly, as you view and work with the DNG images.

> If some other program (such as DxO) takes a RAW file, and converts it to DNG, it may no longer be a RAW file, but rather it is already converted. Somehow LR recognizes it, but is no longer acting as a RAW converter.

Is that right?
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Panopeeper

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Why are DxO DNG files so large?
« Reply #7 on: February 01, 2009, 02:49:32 pm »

Quote from: JDClements
except that it closes itself with no message after running a file
That is meant so; this is a shortcut version of Rawnalyze, intended only to create a structure list.

Quote
But it does not recognize DxO's DNG file: "The image file specification is incomplete or unsupported"
That's ok; pls attach or upload the text file.
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Gabor

JDClements

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Why are DxO DNG files so large?
« Reply #8 on: February 01, 2009, 02:54:28 pm »

Quote from: Panopeeper
That's ok; pls attach or upload the text file.
Ah... there is a file there. Here it is.

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Panopeeper

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Why are DxO DNG files so large?
« Reply #9 on: February 01, 2009, 03:15:14 pm »

This is a demosaiced, linear raw file, every pixel has three components @ 16bits; plus a full image size JPEG preview, over 4 MB. The raw data is compressed losslessly.
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Gabor

digitaldog

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Why are DxO DNG files so large?
« Reply #10 on: February 02, 2009, 12:07:01 am »

Quote from: francois
I could well be wrong but I guess that DxO generates a new DNG file with R,G and B components. This could explain the ~3x big size than the original CR2 file.

Exactly, its simply embedding a rendered RGB document NOT a Raw file within the DNG container. That explains the size and how LR could "see" the edits which would not be possible if the data were really Raw.
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NikosR

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Why are DxO DNG files so large?
« Reply #11 on: February 02, 2009, 04:10:12 am »

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