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?
(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.
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.
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.
Looks like they removed the "Save with Loosy compresion" option. Thats good.
Two main ideas around DNG are:
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.
There's nothing wrong with either way, in my opinion. Adobe is totally committed to the DNG format because they developed it. The Adobe evangelists seem to use it exclusively. I haven't heard of any disasters because someone converted an image to DNG. I have converted some images to DNG. Whenever I create a Panorama from NEF files in Lightroom or Camera Raw the resulting panorama is a DNG file, but that's because Lightroom nor Camera Raw nor Photoshop are capable of creating or saving native raw files. Never have had any problems with the DNG file. On the other hand, I have never had any problems with the NEF files. And the space savings for converting to DNG doesn't seem to be that great when comparing size differential, roughly 15%. I don't see any performance improvement using DNG. So I haven't adopted a DNG workflow. But that's my personal choice.
For sony users there is a minor penalty for converting to DNG. Sony's raw files use a pixel shifting tech that can be stacked for improved range. If you convert them to DNG before stacking in sonys sw you loose that particular sony feature. Their sw can however stack them and output the result as a DNG.
I have a friend who is in the industry of how data formats works, and this person told me that the data is all the same. It simply gets repackaged without gaps. Gaps or spaces increase the file size. Another thing to consider is that proprietary raw files may come with extra unnecessary information. As an example, sometimes raw files will come with partially demosaiced information. And with some software it might come with fully demosaiced meta-data info for all three channels. I've come to believe that there is a lot of information that is under the hood, so to speak, that is unnecessary to process a DNG perfectly.
Take a look at a enhanced DNG and the file gets enormous! What is likely going on there is that the original Raw data is there, but also all of the information for all three channels of the enhanced raw file. Which then likely gets applied when the image is rasterized. And is used all along for the preview we see when adjusting the raw file.
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.
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.