Slow Export to JPG

I found exporting to JPG is a slow process. My computer is running on i7, 8G RAM, Windows 10, SSD. Raw (NEF) file with not many adjustment (some with local adjustment, some without) needs 25 - 40 seconds to export to JPG (744 pixels in long side @300 ppi). I’m not sure whether it is normal performace or my computer is not powerful enough or some configuration I don’t tune up.

Anyone has idea?


YES this is normal performance with PRIME denoising.

Hi Pascal,

I don’t use noise reduction on the photos I export.

I try to apply noise reduction on the same photos for testing, it takes 4 minutes to finish. I can see the difference.

There are more than 30GB free space on SSD. I don’t think it is due to insufficient disk space.

Thanks for your response!

I just tested it on my older I7 Windows 10 machine with 24 gigs of ram. Exporting a fairly heavily edited Canon raw file of around 25mb to jpeg, with PRIME noise reduction added, @ 300 ppi and 100% quality took around 29 seconds. Exporting that same image resampled at 744 pixels, with PRIME noise reduction added, took 23 seconds. Exported the same image without PRIME noise reduction took 9 seconds for the original image and 7 seconds for a version resampled to 744 pixels. While my processing is performed on an SSD drive, the images themselves reside on a normal HDD. Even though you have only 8 gigs of ram, I think your response time is not typical.


Mark, Thanks for sharing your data. The cause maybe amount of RAM. I’ll try to get another computer with similar CPU power but much more RAM to do more testing.

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I don’t think the RAM is your main issue. While it would probably improve things, I suspect something else may be slowing you down. Could you update the RAM in your current machine to 16mb? Are you running other things at the same time as Photolab? Have you analyzed memory and disk usage and performance? Plenty of people are running with 8 gigs and getting better performance than you are.


Hi Mark, it is an ultrabook I carry with in travel. It is impossible to add RAM or alter other hardware configuration.

My ultrabook works normally, The performance is normal when I use CNX2. Ohter than web browser and FastStone, I usually stop other application when I process photos.

I’ll try to figure out the cause of poor performance on my machine.

Thanks again!


I just did some benchmarking on my Mac Mini (Late 2012, 2,6 GHz Core-i7 3720QM, 8 Threads, 16 GB RAM, MacOS 10.14.3) and on my MacBook 12" (2015, 1,1 GHz Core-m3 5Y31, 4 Threads, 8 GB RAM, MacOS 10.14.3). I converted a 24 MP RAW-File from my SONY Alpha-7 to a JPEG with 80% quality.

Mac Mini:
with HQ noise reduction: 10 seconds
with Prime noise reduction: 48 seconds
Memory consumption of PhotoLab2 binary: 1,55 GB

MacBook 12":
with HQ noise reduction: 24 seconds
with Prime noise reduction: 2:10 minutes
Memory consumption of PhotoLab2 binary: 1,31 GB

Just for orientation :slight_smile:


Hi Matthias,

Thanks for your information!

I’m still thinking if I need to clean up my Windows since it has been used for almost 4 years.

Hello @JamesWong,

You can also check if OpenCL is on or off and compare the processing time. And one more thing can affect the time of processing - the size of the virtual memory ( - you can find it in PL logs - OS swap size: XXXX MB - it’s good when you have it > 2GB).

Svetlana G.

Hi Svetlana,

Thanks for your advice!

Well, what do you mean with “clean up”? What’s on the disk is completely irrelevant for processes running in memory.
Regarding memory it’s important how many processes are running at the same time. So you should avoid to run Outlook, MS Office in general, your favorite Internetbrowser etc. at the same time.

Ahh, what comes into my mind: You talked about your Ultrabook
One major problem that some of these devices have is HEAT! Does your Ultrabook have a fan for cooling?

E.g. my above mentioned MacBook 12" has NO fan and an only mediocre heat management. That has the consequence, that all available optional faster CPUs, especially the ‘i7’-CoreM processor, are not faster at all if the load lasts longer than a few seconds because of heat-throttling of the CPU. That’s a protection mechanism such CPUs have to avoid overheating. In case of too much heat the CPU reduces the frequency (or “speed”) of operation until the temperature falls below a specific value of the processor type.

You can see it on my measurements above: The Mac Mini takes 4.8 times the seconds of the HQ noise reduction to create a PRIME noise reduction whereas the MacBook 12" takes 5.4 times. Probably there’s already a slight thermal throttling on the MacBook. (Keep in mind that my MacBook has the slowest and coolest CPU available).

Probably that’s the reason of your performance problems. Perhaps you search for some system tools that show the CPUs operating frequency and other performance parameters (disk I/O, memory consumption, swapping, etc) to gain more insight what’s going on in your machine.

Greetings - Matthias

Hi Matthias,

What I mean “clean up” my computer is cleaning garbage files (esp. temp files), reorganizing file system by utility tools. Since Windows and other applications generate temp files as well as other files which may not be useful anymore but left in harddisk. The purpose is free more empty space for application to execute.

For converting NEF to JPG, in the past days I was using CNX2, I use FastStone Image Viewer to do batch conversion. It can convert 100 edited NEF files in around 90 seconds on the same Ultrabook I’m talking about. You can see the huge difference from the performance by DxO. However, since DxO (also NX-D) adopts sidecar file, FastStone can no longer read edited NEF file. So I have to use the bulid-in export feature from DxO. But the speed on my machine actually slow down the whole process very much. I’m still try to figure out the core reason of my case, esp. the reason of difference from other user.

Anyway, thanks for your sharing!

Hi Matthias,

I do some more export test and comparison this morning. The following test are perfomed on the same Ultrabook, Windows 10 Home, i7, 8GB RAM, SATA SSD with more than 20GB free space.

Task: convert fullsize unedited NEF files to JPG (744 x 496, 100% qualtity, 300 dpi)

Converter: FastStone Image Viewer 6.9
100 D700 NEF files in 46 seconds (in single batch)
100 D850 NEF files in 97 seconds (in single batch)

Converter: DxO PhotoLab 1.2 (without noise reduction)
1 D700 NEF file in 14 seconds (single export)
1 D850 NEF file in 42 seconds (single export)

I don’t write wrong, you don’t read wrong, I don’t test wrong, FastStone is faster than DxO by 30 times (for D700 NEF files) and 43 times (for D850 NEF files).

That is a huge difference on performance.

For your reference, the above two images (1st is from D850, 2nd is from D700) are converted by FastStone in fraction of a second.

Just a thought.

Does CNX and FastStone actually do debayer processing of the nef and then rescale it and save it?
Or so they simply extract one of the embedded jpegs?
Extracting a jpeg instead of processing the nef would be a smart way to do it for cnx as the Nikon’s write fully corrected and processed jpegs into the nef at the time of photo.

An extracted jpeg and exported nef should look exactly the same when created by the camera and cnx.

Hi Required,

First, if you think what FastStone does is a smart way to extract JPG, what do you think the reason DxO does not do the same or similar way?

Second, I do some more test after reading your message. I use FastStone to convert unedited NEF to 8-bit TIF, without changing dimension or dpi, the performance is even better.

For D700 NEF files (4256x2832), 33 seconds to convert 100 images (single batch).
For D850 NEF files (8256x5504), 82 seconds to convert 100 images (single batch).

The quantity of converted TIF file is good. But it is too big to upload here.

Please don’t forget that FastStone Image Viewer is a freeware.

Anyway, thanks for your feedback!


You can try this:
Export an unedited, without any changes jpeg from a NEF with FastStone.
Extract the embedded jpeg from the NEF with exiftool, with this command:
exiftool -b -jpgfromraw /path/to/_image.NEF -w _extraherad.jpg

Compare those two.
Same size?
Some look?
Same exif data?

Hi Required,

I do more test as you suggest and find something interesting.

First, the sizes of JPG from FastStone and Exiftool are different.

Second, EXIF is empty in JPG extracted directly from NEF by Exiftool while EXIF is correct in JPG converted by FastStone.

File converted by FastStone is slightly smaller and with EXIF data. File extracted directly from NEF by Exiftool is slightly larger and without EXIF data. Intesting enough!

Also, this may show us that FastStone does not extract embeded JPG image directly from NEF file.

For naked eyes, two JPG images are same.

Nice to exchange ideas with you!

Very nice work!

Yes, the size differences you see come from lack my exif data.
So now we know that FastStone simply extract the embedded jpeg and the exif data from the NEF and then writes the exif into the jpeg.

Thanks you very much for the tests!

I guess PL always uses the non debayered RAWs and on top of that add their adjustment layers - which explains the great quality they produce - where some other developers are exporting post-debayered and pixel based images like TIFFs which will be much faster.

And on the Mac it’s a bit worse even because PL does not use my GPUs at all. It punishes my 8 CPU cores to the max although that’s efficient it feels a bit old school not utilizing both my GPUs as well as the CPUs to process the NEFs.

Hi Required,

You may misunderstand something I wrote.

The file size of JPG from FastStone is 3,055,760 bytes (smaller) with EXIF while the file size of JPG from Exiftool is 3,063,782 (larger) without EXIF.