DNG vs. CR2

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DNG vs CR2 – which is best?

In Mastering Lightroom: Book One – The Library Module I recommend converting your Raw files to the DNG format when you import them into Lightroom. The question naturally arises as to whether there is any loss of quality during the conversion. Is it possible that there is information of some kind in your camera manufacturer’s proprietary Raw format that Lightroom can’t read, or is somehow omitted from the DNG file during the conversion process?

The easiest way to find out is to carry out a test. I’ve only been converting my Raw files to DNG for a short while, so I still have plenty of Canon .CR2 files that I can use as a comparison. If you use a different brand, or even a Canon camera other than mine (an EOS 5D Mark II) feel free to carry out a similar test yourself (in fact, it’s probably wise – see the note about Fujifilm cameras at the bottom of the article).

DNG vs CR2 – which is best?

DNG vs CR2 – which is best?

Here’s how I did it:

I chose three .CR2 files to test, each with different qualities:

  • A landscape with a blue sky to see if there is any difference in the graduation between light and dark tones.
  • A portrait, to see if skin tones are affected.
  • A photo taken at ISO 6400 to see if there is any difference between the two formats when it comes to high ISO noise reduction (all three displayed above).

I copied the three .CR2 files to a new folder, and made a duplicate of each. That gave me six Raw files in total. I imported the first three into Lightroom, retaining the .CR2 format. Then I imported the three duplicates, using the Copy as DNG option to convert them to the DNG format and save them in the same folder.

I went to the Collections containing the original photos, copied all the Develop settings, then returned to the newly imported images and pasted the Develop settings. That gave me two versions of each – one generated from a .CR2 file and the other from a DNG file, each one identically processed in Lightroom.

Then I exported each of the six images as JPEG files at the 100% quality setting without any resizing or additional sharpening. Finally, I opened the JPEG files in Photoshop and viewed them at 100% magnification to see if I could see any difference between the photos generated from .CR2 or DNG files.

The result? All three pairs of images were identical. I couldn’t spot a single difference between any of them.

That’s an ideal result, because it gives me the full confidence to convert my Canon .CR2 Raw files to DNG and discard the originals. I know I’m not losing anything.

Here are some samples so you can see for yourself (100% enlargements):

DNG vs CR2 – which is best?

DNG vs CR2 – which is best?

DNG vs CR2 – which is best?

A few things to bear in mind when converting Raw files to the DNG format:

  • Converting to DNG saves space (the files are up to 20% smaller).
  • Converting to DNG makes Lightroom run faster if you include Fast Load Data. The setting is found under the File Handling tab in Preferences (see below). According to Adobe, you will see a difference in the speed at which Lightroom renders previews of up to eight times. I’ve noticed a visible difference in speed since I started using DNG.

DNG vs CR2 – which is best?

  • If you tick the Embed Original Raw File box under the File Handling settings Lightroom embeds a copy of the original Raw file in the DNG file. You can then extract it, if you want to, using Adobe’s free DNG converter software. However, this does negate the space saving advantage of DNG.
  • Some software doesn’t recognise the DNG format. That includes Digital Photo Professional (DPP), Canon’s proprietary Raw conversion software. If you use an application other then Lightroom, it’s a good idea to confirm whether it can open DNG files. This will help you decide whether to use the format.
  • Some Fujifilm camera users have reported problems with converting Raw files to DNG. I don’t own a Fujifilm camera and haven’t tested it myself, but the solution appears to be in the Compatibility field of the File Handling tab. Selecting the most recent option seems to give the best results.



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2 Responses to “DNG vs. CR2”

  1. Stephen says:

    RAW converters evolve and improve with time. You don’t see any difference now between CR2->DNG->TIFF and CR2->TIFF because you are using the same version of software from Adobe. But perhaps in 12 months or 24 months Adobe will improve the algorithms to convert CR2 files. If that happens, the CR2 file may contain more information than was extracted by the out-dated CR2->DNG conversion that was performed earlier.

    I can’t predict the future, but I have seen steady improvement in the quality of RAW->TIFF conversions over the past decade. The Fuji X-Trans sensor is perhaps more likely to see future improvement than the fairly stable Canon Bayer CR2 format, but who knows. I’m not deleting my CR2 files.

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