File size of exported DNG is more than 4x larger than original RAW file

First I must say that DeepPrime is an amazing feature! It works perfect with the RAW files from my Olympus EM1ii and EM1iii. I never got pictures with so much details and so little noise at all ISO levels. I can increase max. ISO setting by 1 to 2 steps with DeepPrime!

Currently I am using LR (sorry) and PL4 can still not fit all my needs.
I’m testing the PL4 trial now and would like to buy it to integrate it into my Workflow with LR.

But I wonder why the DNG file size when exporting as DNG (Noise reduction… only with Lens sharpening activated) produces so big files. With an .ORF file of 18MB it produces a DNG > 80MB.
As a result I will need 5x the diskspace to store my files! (this is no problem for working, as HDs are getting bigger and bigger, but for archiving this big amount of data matters!)
Is this normal or is there a bug in DNG creation (e.g. no compressing, embedding original raw, …)?

Another thing I couldn’t find yet: When exporting to Lightroom PL4 always adds a Suffix “_DXO”. It is possible to disable this suffix like for other exports?

kind regards

Did you compare it with a dng file created by lr?


This seems to be in the queue for development:

DPL creates “linear” DNGs. They contain demosaiced images and therefore consume more space.

While a raw image contains r/g/b/g pixels, a demosaiced image is composed of rgb/rgb/rgb/rgb pixels. Raw pixels are 12-14 bits deep vs. 16 bits in a demosaiced image file. In total, you get the approx. size change mentioned above

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Adobe created some confusion with DNG in that a DNG can be a raw file or it can simply be a container for effectively a demosaiced raw file, effectively a Tif file.

The same thing happens in LR if you create a hdr or a pano. The cynic in me might think that the confusion may be deliberate as users believe that they are using an all raw workflow. Adobe would never do that :slight_smile:

You might want to take a look at this short video on using MFT and DXO:

How and why I use DxO PhotoLab to Process Micro 43 RAW Files

It is also worth bearing in mind that LR only uses the jpg correction embedded in the raw file and you can get significantly better lens corrections with DXO, particularly at the wide angle range. DXO lets you use the true focal length of certain lenses (eg Olympus 12-100mm Pro) giving you a wider view and less resizing of the image to get back to full size after the crop. The jpg correction will crop the image to give you the focal length quoted on the lens.

Also you can use the DCP colour profiles you have in LR in DXO if you wanted to.



Tanks for all the answers!
I must admit that I never used DNG before, so I didn’t know details about it. I just thought it is another type of raw format.

I’m currently contemplating purchasing Photolab 4 and have carried out enough evaluations to be convinced that the noise reduction and raw demosaicing is very much superior to Lightroom. However, I’m invested in LR’s catalog and use smart collections extensively, so I’d like to export my images from Photolab to LR. I too have noticed that the file sizes are humungous. It doesn’t matter if I export DNG or 16 bit TIFF, the file sizes are far too large. I understand that DxO stores the fully de-mosaiced image in DNG, but why can’t it apply compression? Same goes for TIFF. For example, Photoshop gives me two methods of compressing 16 bit TIFF files. Right now, this is a showstopper. My exported a7RIV files are well over 200 MB!

In my former workflow, when I imported raw files into LR and converted them to DNG using lossless compression, they shrunk down to 40 MB. Now I’m stuck with files that are 6x in size.

Does anyone have any ideas?

When you convert files in LR to DNG they are still raw files, the same as if you used Adobe DNG converter. DXO can work with these files as long as they support the camera that produced the original raws and they are standard conversions to DNG. As Adobe invented DNG they can do what they like and all Adobe software will be able to read them. Once you start using options then this breaks compatibility with other software.
I downloaded a Sony a7Riv file just to understand the file sizes.

The Sony raw file was - 120Mb
Converted with Adobe DNG converter - 45Mb
DXO DNG export - 186Mb
DXO Tif - 354Mb
Tif LZW Compression - 397Mb
Tif ZIP Compression - 305Mb

Tif compression doesn’t do much for you and the LZW option actually increases file size. I thought it did when you mentioned PS having two options but thought I had better check before posting as it is counter-intuitive :slight_smile:

So whether you are using LR or DXO as soon as you produce a RGB file you have to deal with the same sized files.

If the DAM is vital for you then unfortunately DXO, although it has a Photolibrary option, it is not a DAM and you need to stay with LR.

This is one of the drawbacks of using a combined raw converter and DAM, you are effectively locked in.

As a general comment this applies to anyone using a combined raw converter/DAM program.

For people who a DAM is vital (not most DXO users as it doesn’t have DAM functionality) it might be worth considering using dedicated DAM software. This separates the DAM and raw converter functionality which means changing raw converters becomes a minor factor. There are several options but one of the most popular is IMATCH. Currently on sale in Dec for 25% off, if anyone is contemplating a Christmas present for themselves :slight_smile:

I don’t need a DAM for photos but I am looking at it for a DAM application as it supports Office, PDF, MP3 and all other files.


so compression is 2 2/3. how does that work?, because a rawfile has basicly a tiff like datafile. (if i am correct in memory)

and of caorse this DNG is ONLY readable by Adobe products… Right? :face_with_hand_over_mouth:

Found there page.

If i read this i get the impression that the 45Mb holds a lossy jpeg.

I’m not a LR user myself, but I understand that it’s possible to continue using LR for it’s cataloguing features without having to pay a ongoing usage fee … whilst using PL for your RAW processing.

John M

My bad, the lossless option was on in the DNG converter. They are in a sub menu so not visible on the main page. Must have been playing with compression last time I looked at it. The Sony files are 65Mb without compression.

Importantly as you say the lossless files are not readable by DXO. The standard DNG converted files are readable by DXO.

The amount of compression you get with DNG converter varies with the source raw file. The Sony was giving a significant reduction of around 45% but with an Olympus 20Mp .orf, it went from 18,302Kb to 18,134Kb. So not so much. Again this DNG file was compatible with DXO as it comes from a supported camera.

Other software can open lossy compressed DNG files, for example Affinity Photo. They are not doing anything fancy at the raw level, unlike DXO, so they can use the DNG code.


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