Lightroom DNG file size

Forum|Forum|5 years ago
June 10, 2020
4 replies
2690 views

I use Sony A7R4. an uncompressed raw file from the camera is as big as 120Mb. However, after I import this file to Lightroom and convert to DNG, the size shrinks down to about 60Mb. Is it normal? Don't I lose any data during conversion? If so, is there any way to maintain the original file size?

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Camera Raw Fan

Known Participant

I was told by someone in the industry that all the same data is there, that it gets repackaged to where there is no gaps in the information which condenses the file size.

JP Hess

Inspiring

The size differential varies from one camera manufacturer to another. The information about DNG conversion from Adobe states that space savings can be as much as 50% or more. When I convert my NEF files created by my Nikon camera I only realize About a 15% reduction in size. But I don't think it is unreasonable or unrealistic to think that the size can be reduced by 50%, and you can retain the original file and compare them and wear yourself out trying to discover any quality loss. But I seriously doubt you will be able to find any.

Curt Wrigley

Inspiring

Curious why you convert to DNG. There are lots of valid reasons; just curious

I assume you are using classic. Check that you are not checking the box called "do lossy compression" in the dng dialog. That makes the files a lot smaller but does loose some information. With that not checked the file size reduction is normally in the 30% range from the original raw.

S

Sung JoonAuthor

New Participant

Thanks for the comment! Well, I use DNG just because I thought it was the best way to edit photos in Lightroom. Silly answer... Anyway, I do use the newest version of Lightroom Classic CC in which I couldn't fine 'the box called <do lossy compression> in the dng dialog.' I instead found the "embed original raw file' check box in the <file handling> window of <Preferences>. When I check it, the size between the orginal raw and the converted DNG are about the same. But I gather it is unchecked by default.

Curt Wrigley

Inspiring

Forgive me,

Looks like they removed the "Save with Loosy compresion" option. Thats good.

Two main ideas around DNG are:

It is smaller file size than the original camera's raw file; yet still maintains all the infomration for raw editing (no loss of quality). Adobe says there is a minor performance improvement editing DNG vs camera raw; but I havnt noticed that.
All camera manufactures use a differen raw file format. What happens if you save all your photos in your camera's raw format and they go out of business or stop supporting that format. DNG is adobes invention to make a standard RAW format to avoid this issue.

However; I think the chances of Sony, Nikon, Cannon going out of business and stopping support for their raw format is about as likely as Adobe going out of buisness. Others will disagree.

Personally I leave everythning in camera raw; one less step in the import process. (though LR now does the DNG conversion in the background; so that is a minor point). You cant go wrong either way imo.

Rob_Cullen

Community Expert

(Disclaimer: Not a Sony user.)

I downloaded a test ARW file that was 117Mb and in the Lr-Classic Library converted it to DNG- the result being a 53Mb file.

So your result 120>60 seems possible.

DNG conversion is always known to preserve the full image raw data, so I have no idea what other proprietary metadata may be getting deleted/re-arranged in the DNG file.

Regards. My System: Windows-11, Lightroom-Classic 15.0, Photoshop 27.0, ACR 18.0, Lightroom 9.0, Lr-iOS 10.4.0, Bridge 16.0 .

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