RAW (DNG) compression on or off

[kivis]

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Anyone have any real life comparison between RAW (DNG) compression on or off? 

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[pgk]

Its easy to test!

[jaapv]

You won't see any difference, as this is lossless compression, i.e. the original file will be reconstructed 1:1 from the compressed file.

[marchyman]

What Jaap said.  The only difference is it may take an extra millisecond or so to compress/decompress the image when saving/viewing/processing.  I doubt that is something you'd notice.

[Avvie]

what's the difference in file size?

waiting for my m240, it's being investigated at the store. 😞

[a.noctilux]

1 hour ago, Avvie said:

what's the difference in file size?

waiting for my m240, it's being investigated at the store. 😞

For M(typ 240), 47 MB

compressed variable from 24 MB to 31 MB depending on the density of the pic.

You would make some comparisions then decide to go for compressed or not.

 

As side note, my choices after comparing the outputs earlier:

- on M240, I use compressed files recording

- on M246, Monochrom, I use non-compressed files since years, files are smaller at about 36 MB

[kivis]

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I can not see any difference except file size is smaller.

[jdlaing]

7 minutes ago, kivis said:

I can not see any difference except file size is smaller.

You’ve discovered the secret.

[jaeger]

In the audiophile world, some people claim they can hear the differences between lossless and uncompressed music.  I can't tell and neither in photos, but I do believe some people have higher sensitivity in certain things. 

My question would be the access speed when operating these files in LR catalogue (or other apps) for browsing, selecting, editing, etc.  I have been using uncompressed DNG because I want to avoid sluggishness in LR and memory is affordable.  Actually I don't know if LR copies DNG as-is or auto uncompressed lossless, does anyone know?  My guess is uncompressed to increase the performance of the LR.

[tedd]

On 7/10/2021 at 10:41 AM, jaeger said:

In the audiophile world, some people claim they can hear the differences between lossless and uncompressed music.

I make my living in the audiophile world and those people are full of crap 😗

[pop]

Am 10.7.2021 um 02:41 schrieb jaeger:

can hear the differences between lossless and uncompressed music

Yes, it's been well documented. It's called placebo.

[pop]

Am 10.7.2021 um 02:41 schrieb jaeger:

My question would be the access speed when operating these files in LR catalogue

In a typical PC (of any make) the processor outperforms its storage. You will save much time when copying, moving and processing compressed images. This becomes perceptible when copying the images from the SD card or from the camera's memory as well as when doing a backup of your image archive and, of course, whenever you handle an image file. The same applies to moving the images over a network. Smaller files move faster.

Conceivably, you might even save time in-camera by saving compressed images, but this depends on many technical details. Why not just try? Saving a digital image to a storage card does not cost anything but a bit of your time.

[Monochrome_Man]

Been there done that.... there IS NO difference between compressed vs uncompressed in image quality;

only one thing is: saving time coping, and less storage consumption. Thad it. Just set to compress files and forget about it

 

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Edited July 13, 2021 by Monochrome_Man

[Krusty]

I am also currently testing that compression feature in Lighroom Classic. There are two ways to reduce the file size

- Library Module --> Right click on photo --> Metadata --> Update DNG Preview and Metadata: This results from for my Leica Q2 Files from 80 MB to 52 MB (!). I do not have any idea what this feature does to get that small size because the file is still not lossy compressed

- Library Module --> Menu Library --> Convert Picture to DNG --> Use Lossy compression: This results into 15 MB (!!!!) for my Leica Q2 files. That is what i was used to have when i made an JPG Export with 85% Quality ... 

Maybe anyone can describe more about this two features and what the disadvantaged of both are? In the lossy compression there must be some information removed from the file but it seams to be better than jpg otherwise they wouldnt have it implemented and just told you that you should use jpg when you want to save disk space instead... 

[marchyman]

• Lossless compression ==> a decompressed image is exactly the same as the original image
• Lossy compression ==> a decompressed image is not the same as the original image

With lossy compression you may not notice any difference or may only notice a difference on some images.  However, every time the image is re-edited and re-compressed you will lose more info.   Re-edit enough times and the error artifacts become quite noticeable.  I will never use lossy compression on my raw files.  I am happy that the M gives me an option for lossless compression.   I wish my Q did the same.

 

[jdlaing]

Lossless compression simply removes needless metadata to reduce file size. Generally the image quality remains unchanged.

[pop]

vor einer Stunde schrieb jdlaing:

Lossless compression simply removes needless metadata to reduce file size. Generally the image quality remains unchanged.

Not quite.

Compression reduces the amount of storage required to keep the bulk of the image, i.e. the image data. There are several techniques to do that; two of the more prominent ones are:

• Run length encoding: whenever the same value occurs several times in a row, you note the value just once and note how many times it occurs.
• Huffman encoding: you count how many times each individual value occurs in the whole image, then you assign a short sequence of bits to the values which occur most often, and long strings of bits to the values that occur but rarely. That is comparable to the Morse alphabet where the most frequent letters are very short and the less frequent letters are longer; this saves much time transmitting lengthy texts.

There are, of course, more procedures; different formats in the industry might apply several of those procedures to the same file for maximal compression or for optimal performance or whatever reasons the designers fancied.

The 'lossless' procedures are all reversible: they provide enough information for the receiving computer to exactly reconstruct the original image data, bit by bit.

That's the difference to lossy compressions, where some of the data is simply discarded.

Edited August 3, 2021 by pop

[jdlaing]

14 minutes ago, pop said:

Not quite.

Compression reduces the amount of storage required to keep the bulk of the image, i.e. the image data. There are several techniques to do that; two of the more prominent ones are:

• Run length encoding: whenever the same value occurs several times in a row, you note the value just once and note how many times it occurs.
• Huffman encoding: you count how many times each individual value occurs in the whole image, then you assign a short sequence of bits to the values which occur most often, and long strings of bits to the values that occur but rarely. That is comparable to the Morse alphabet where the most frequent letters are very short and the less frequent letters are longer; this saves much time transmitting lengthy texts.

There are, of course, more procedures; different formats in the industry might apply several of those procedures to the same file for maximal compression or for optimal performance or whatever reasons the designers fancied.

The 'lossless' procedures are all reversible: they provide enough information for the receiving computer to exactly reconstruct the original image data, bit by bit.

That's the difference to lossy compressions, where some of the data is simply discarded.

What is Lossless Image Compression and How it Works

Lossless compression means that you reduce the size of an image without any quality loss. Usually, this is achieved by removing unnecessary metadata from JPEG and PNG files. We say “usually” because, with some other compression algorithms, like Imagify’s, other compression opportunities are leveraged without sacrificing the image’s quality. 

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Hallo,

Look here: Leica M

[pop]

Whatever your source, they have it wrong. Have you ever looked at the specification of the DNG format? Have you ever used compression software?