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Author Topic: DNG half the file size of Pentax prop. RAW?  (Read 4074 times)
The View
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« on: May 07, 2008, 02:14:51 PM »
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When I erased my import back-ups (after manually updating the image library, of course), I noticed :

1. Lightroom didn't convert these to DNG like all the "originals".

2. The file size of the non-converted Pentax RAW files was twice the size of the same image in DNG.


How is such a difference in file size possible?

And why didn't Lightroom convert the back-ups to DNG, too? (did I miss a box to check?)
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DarkPenguin
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« Reply #1 on: May 07, 2008, 02:35:10 PM »
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Does pentax compress their RAW files?
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Panopeeper
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« Reply #2 on: May 07, 2008, 02:47:02 PM »
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2. The file size of the non-converted Pentax RAW files was twice the size of the same image in DNG.
How is such a difference in file size possible?
There can be several reasons for that. Which model are you referring to?

If you upload such a PEF file (yousendit.com), I take a close look at it.
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Gabor
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« Reply #3 on: May 07, 2008, 06:12:39 PM »
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And why didn't Lightroom convert the back-ups to DNG, too? (did I miss a box to check?)[a href=\"index.php?act=findpost&pid=194210\"][{POST_SNAPBACK}][/a]
That's just what it does.  The backup copy made on import is of the original file, so if there's a problem you can go back to the start.  That makes sense for some people, but I've actually found it to add complexity, especially when trying to achieve unique filenames.

You'll notice it doesn't rename the backup copy, let alone convert to DNG.  This can make it awkward to match up the backups with the renamed files later, and in my own workflow I use an ingester external to LR which copies/renames/etc the files and THEN duplicates them.
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Samotano
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« Reply #4 on: May 07, 2008, 09:19:15 PM »
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When I erased my import back-ups (after manually updating the image library, of course), I noticed :

1. Lightroom didn't convert these to DNG like all the "originals".

2. The file size of the non-converted Pentax RAW files was twice the size of the same image in DNG.
How is such a difference in file size possible?

And why didn't Lightroom convert the back-ups to DNG, too? (did I miss a box to check?)
[a href=\"index.php?act=findpost&pid=194210\"][{POST_SNAPBACK}][/a]
Perhaps Pentax does not compress their RAWs.  My point & shoot panansonic LX2 has uncompressed raw too; converting them to DNG reduces them to almost half their original size.
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The View
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« Reply #5 on: May 08, 2008, 02:44:12 AM »
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That's just what it does.  The backup copy made on import is of the original file, so if there's a problem you can go back to the start.  That makes sense for some people, but I've actually found it to add complexity, especially when trying to achieve unique filenames.

You'll notice it doesn't rename the backup copy, let alone convert to DNG.  This can make it awkward to match up the backups with the renamed files later, and in my own workflow I use an ingester external to LR which copies/renames/etc the files and THEN duplicates them.
[a href=\"index.php?act=findpost&pid=194259\"][{POST_SNAPBACK}][/a]

Actually it does rename the file names, but keeps (of course) the PEF filename ending for Pentax.

I usually don't keep those back-ups for long. I just copy the Lightroom images folder to my external hard drive, so I have an exact copy of it, and when I'm done with that, I erase the import back-up.

For me, the import back-up is just in case something goes wrong at the import.
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The View
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« Reply #6 on: May 08, 2008, 02:46:32 AM »
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Does pentax compress their RAW files?
[a href=\"index.php?act=findpost&pid=194217\"][{POST_SNAPBACK}][/a]


It's the other way round: the original Pentax files are TWICE the size of the DNGs.

It's like converting Pentax RAW files to DNG would shrink them by 50%.

I mean converting to DNG, not compressing.

I found out about it when I erased the import back-up copies, and just wondered how much space that had taken up.
« Last Edit: May 08, 2008, 02:47:32 AM by The View » Logged

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DarkPenguin
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« Reply #7 on: May 08, 2008, 07:46:48 AM »
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DNG compresses the RAW data.  So if pentax doesn't the DNGs will be much smaller.
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The View
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« Reply #8 on: May 08, 2008, 12:55:45 PM »
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DNG compresses the RAW data.  So if pentax doesn't the DNGs will be much smaller.
[a href=\"index.php?act=findpost&pid=194355\"][{POST_SNAPBACK}][/a]

Is it a lossless compression?

Or would it be better for the image quality to leave a RAW file at its original format.

My next camera, for example, will be very likely the Nikon D300. I wouldn't want to compromise any of this quality. I'd rather buy more hard drives.
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DarkPenguin
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« Reply #9 on: May 08, 2008, 01:30:41 PM »
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Is it a lossless compression?

Or would it be better for the image quality to leave a RAW file at its original format.

My next camera, for example, will be very likely the Nikon D300. I wouldn't want to compromise any of this quality. I'd rather buy more hard drives.
[a href=\"index.php?act=findpost&pid=194404\"][{POST_SNAPBACK}][/a]

It is lossless.
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Panopeeper
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« Reply #10 on: May 08, 2008, 02:00:51 PM »
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This is quite a worthless excercise.

1. A DNG file *may* be compressed it it *may not* be. Obviously, if it is MUCH smaller than another version, then it IS compressed.

2. The PEF files of *some* models are compressed, *some others* are uncompressed but packed (which too is a compression).

3. The PEF files contain a prewiev image (beside the thumbnail), which can be of considerable size; I saw one 1.3MB large; again, this depends on the model, and of course on the actual image.

4. The DNG file always contains a thumbnail, but it *may* contain a mid-sized or a large preview as well.

5. The method of compression adopted in PEFs and in DNG is roughly the same. However, when compressing in a computer, the algorythm can be fine-tuned and produce a considerable smaller file than the in-camera compression.
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Gabor
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