Understanding file size: CR2 vs. DNG

[stillwatergal]

Ok, I know I'm not really great on numbers and clearly don't have a full understanding of DNG but why is a DNG file sooooooo much larger than a RAW CR2 file? (17.59 mb vs. 31.53 mb when taken with my XSi)?
Thanks!
Stephanie

[yoshi]

Re: Understanding file size: CR2 vs. DNG

Ok, I know I'm not really great on numbers and clearly don't have a full understanding of DNG but why is a DNG file sooooooo much larger than a RAW CR2 file? (17.59 mb vs. 31.53 mb when taken with my XSi)?
Thanks!
Stephanie

Hi Stephanie, welcome to DPNow.
This is rather a question to you than an answer to the above, as I do not think I myself have a good knowledge about this aspect, either.

Are you saying that DNG is a way larger in file size than CR2 or a manufacturer's propreietary RAW file?

If I may put my understanding, which could be wrong as I implied earlier, CR2 contains some unique "additional info" such as "picture style" that are used only by CR2 and not utilized by DNG. So when converting from CR2 to DNG, those additional info is discarded. So DNG file is usually a bit smaller than CR2, although DNG is another RAW file format proposed by Adobe.

I also want to learn more about it. Looking for help from more informed people.
yoshi

[rogleale]

Re: Understanding file size: CR2 vs. DNG

Hi Stephanie,

This happens sometimes because some RAW files are compressed in the camera, I don't know about CR2's, but such a big difference is surely because you have chosen to include the original RAW file in the DNG. Have to check your preferences!

Roger

[Ian]

Re: Understanding file size: CR2 vs. DNG

I think Roger is right, Canon RAW files are compressed (which means they won't all have the same file size). DNG files are compressed too, but either they store additional information or the compression is not as efficient; my Olympus RAW files converted to DNG see about a 10% increase in file size, but a doubling of the size would certainly suggest that you have embedded the original Canon RAW file inside the resulting DNG file.

Assuming that you are using the Adobe DNG converter to create DNG files, there is a preference option to embed the original file.

Ian

[stillwatergal]

Re: Understanding file size: CR2 vs. DNG

OK.... I use LR to import and convert and I have checked my preferences. Of course, I had
checked the box that says to "embed the original RAW file" in the DNG conversion. So now I understand what I originally asked.
Of course :-), this leads to the follow up question.... why should one (or shouldn't one) embed the original RAW file? What is the upside of doing it that way? Is there a downside of not embedding the RAW file?
Stephanie

[Ian]

Re: Understanding file size: CR2 vs. DNG

OK.... I use LR to import and convert and I have checked my preferences. Of course, I had
checked the box that says to "embed the original RAW file" in the DNG conversion. So now I understand what I originally asked.
Of course :-), this leads to the follow up question.... why should one (or shouldn't one) embed the original RAW file? What is the upside of doing it that way? Is there a downside of not embedding the RAW file?
Stephanie

I think it's just down to personal perference to be honest. I prefer to have separate files.

Ian

[stillwatergal]

Re: Understanding file size: CR2 vs. DNG

So, Ian, if (on import) you don't check the embed original RAW file box, does LR keep 2 files (CR2 and DNG) or does it create the DNG and discard the CR2? What if you convert after import?
Stephanie

[Ian]

Re: Understanding file size: CR2 vs. DNG

So, Ian, if (on import) you don't check the embed original RAW file box, does LR keep 2 files (CR2 and DNG) or does it create the DNG and discard the CR2? What if you convert after import?
Stephanie

Yes, I believe it looks for any files with the same file name, which could be JPG, RAW, TIF, DNG, etc. and imports all 'versions'. This may be user-configurable, but certainly seems to be the default.

Ian