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Exporting DNG With Full-Size Preview From DNG with Small Preview

Forum|Forum|25 days ago
April 27, 2026
7 replies
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I received a batch of DNG files from one of our freelance photographers that have small previews. I imported these into Lightroom with the expectation of being able to export a new batch of DNG files with full-size previews. However, all I can get is files with the same small previews. There are 2 reasons I need full size previews.

1-We use Photo Mechanic for culling and ordering images before renaming and processing them through LR.

2-Our DAM relies on extracting the JPEG embedded in the DNG files for downloading.

Am I missing a setting somewhere, or is there really no way to force LR to create a DNG file from scratch with a larger preview?

Thanks,

Correct answer Per Berntsen

So the Z7 produces DNG files? I thought it only creates NEF files like other Nikons.

Sorry, I forgot about the DNG conversion. All Nikon cameras create NEF files.
So, as mentioned by @Rob_Cullen , the files have been converted to DNG either by LrC or the DNG converter.

The conversion doesn’t touch the image part of the file (except the embedded preview) – DNG is a different “wrapper”, but the content is unchanged.
But it’s possible that having the original NEF files would have been more trouble free – I always shoot full resolution, so I don’t know.

You mention that you use Photo Mechanic, so I’m curious to know if you cold view these files in PM?
And, as I touched upon earlier, comparing before/after file sizes does not provide any indication of the embedded preview’s dimensions.
The file size size of a jpg can vary wildly, depending on image content.

Per Berntsen

Correct answer

Community Expert

So the Z7 produces DNG files? I thought it only creates NEF files like other Nikons.

Sorry, I forgot about the DNG conversion. All Nikon cameras create NEF files.
So, as mentioned by @Rob_Cullen , the files have been converted to DNG either by LrC or the DNG converter.

The conversion doesn’t touch the image part of the file (except the embedded preview) – DNG is a different “wrapper”, but the content is unchanged.
But it’s possible that having the original NEF files would have been more trouble free – I always shoot full resolution, so I don’t know.

You mention that you use Photo Mechanic, so I’m curious to know if you cold view these files in PM?
And, as I touched upon earlier, comparing before/after file sizes does not provide any indication of the embedded preview’s dimensions.
The file size size of a jpg can vary wildly, depending on image content.

Per Berntsen

Community Expert

I’ll insist that she just give us the image files straight from her camera

I’m pretty sure that these files are straight from the camera, and that it has been set to Raw M (Medium) under Image size in the Photo shooting menu.
I checked the menus on my own Z7, and the M option produces files that are 6192 x 4128.
Tell her to use the L (Large) option, which is full resolution.
Although the two other options, M and S, have raw in their name, they do not produce true raw files.

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icurate2005Author

Known Participant

So the Z7 produces DNG files? I thought it only creates NEF files like other Nikons.

I’m pretty sure that these have been run through Lightroom and renamed upon export of the DNG file. Are the files created in-camera still NEF files then? What a can of worms this has opened. I appreciate your time on this. My staff photographer and I are learning a lot.

Rob_Cullen

Community Expert

Nikon raw files are NEF file-type. https://www.zsystemuser.com/z-mount-cameras/z-camera-articles/file-types-created-or-used.html

If you are receiving DNG files then they have been ‘modified’ or ‘converted’ to DNG by some process.

I appreciate the replies from @Per Berntsen about the camera file options that provide great info on the topic.. In particular references to original file size.

Regards. My System: Windows-11, Lightroom-Classic 15.3, Photoshop 27.5, ACR 18.3, Lightroom 9.3, Lr-iOS 10.4.0, Bridge 16.0.3 .

Per Berntsen

Community Expert

I downloaded your two DNG files and imported them in LrC, and both report the preview size to be 6192 x 4128.

Although they open without issues in Adobe applications, other applications cannot open them.
Windows Photos and ACDSee Home (that cannot read raw files, and display the embedded preview) both have issues with them.
Photos says that the format is not supported or the file is damaged, and ACDSee just displays a black box. Probably because because they don’t support the format; see Mosaic Data: No in the screenshot. That indicates that this is a linear DNG, not a raw file.
The files have probably been shot as Small raw – the full resolution for the Nikon Z7 II is 8256 x 5520.

I routinely convert all raw files to DNG with Medium size previews (using the DNG converter) before importing. I did a test export of one file with the preview set to full size, and it worked as expected.
The original is 52.5 MB, the exported file 54.7 MB. The image in question is predominantly sky and water, which compresses easily, which explains the small increase in file size.
The difference would have been much bigger with an image containing lots of sharp detail (or noise). This is how jpg compression works.

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icurate2005Author

Known Participant

Thank you for taking the time to do this. There is definitely something weird about her files and you have helped me understand what that is. We have decided to avoid using her in the future and, if we do, I’ll insist that she just give us the image files straight from her camera as all of our other photographers do. At least that way I have some options to work with those files.

Rob_Cullen

Community Expert

This thread is a learning experience for me and I am curious.

From my searching I have a suggestion-

In the LrC Preferences > File Handling > Import DNG Creation > Set JPEG Preview [Full Size] and re-import the originals.

Then try you Export with Full-Size in the export dialog.

Anything I have done to export your ‘original’ DNG file has resulted in a file that contains a full-size preview- according to Exiftool data.

Perhaps your DAM app is pulling the wrong preview from the exported file.(But that is beyond my knowledge). If I am not helping just ask me to ‘butt out’ .

There are some relevant threads from @johnrellis who is far, far, more knowledgeable than me- eg. This one regarding a bug about embedded previews-

Regards. My System: Windows-11, Lightroom-Classic 15.3, Photoshop 27.5, ACR 18.3, Lightroom 9.3, Lr-iOS 10.4.0, Bridge 16.0.3 .

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icurate2005Author

Known Participant

As much effort as you are putting into being helpful it would be damn rude of me to tell you to butt out. You are also the only one trying, so I definitely appreciate your efforts.

Taking your screenshots in order, my ‘import DNG creation’ was already set to full size. The metadata height and width you are looking at is for the actual image, not the embedded preview. I can tell the preview size isn’t changing just based on the final file size. A larger preview adds substantially to the file size and these files are ending up the same size. I’m going to move this over to feature requests as it seems that this is really something that LR can’t do for some reason. Thank you again for your efforts.

Thanks again,

I

icurate2005Author

Known Participant

Here are updated links to the original DNG and the DNG exported from Lightroom with the settings in the screenshot I attached elsewhere in this thread.

SampleLRexportwithsmallPreview.dng

SampleOriginalDNGwithsmallpreview.dng

Rob_Cullen

Community Expert

I am no export in this field, but I do know (by experimenting) that the Adobe DNG Converter will ‘convert’ DNG files to DNG files with the option for Full-size previews, option set in the preferences.

Give the DNG Converter a go on a Folder of DNGs. (Lightroom-Classic is not involved.)

Regards. My System: Windows-11, Lightroom-Classic 15.3, Photoshop 27.5, ACR 18.3, Lightroom 9.3, Lr-iOS 10.4.0, Bridge 16.0.3 .

I

icurate2005Author

Known Participant

Not working with this either. Here are my settings.

I

icurate2005Author

Known Participant

Here’s a link to a sample image in case anyone wants to try this themselves.

I’d love for someone to prove me wrong.

SampleDNGwithsmallPreview.dng

Srishti Bali

Community Manager

Hi @icurate2005

Thanks for sharing the details. To better understand what’s happening with the DNG previews, could you please help with a bit more information?

Version of Lightroom you are exporting from?
Where are you exporting the DNG from? (Original RAW, existing DNG with small preview, etc.)
Export settings used for the DNG (Preview size option, compression, compatibility) - Platform and OS version
Can you share a few screenshots or a screen recording explaining the issue?

This will help determine whether the behavior is expected based on export settings or if something else is at play.

Thanks, Srishti Bali | Community & Engagement Strategist, Digital Imaging | Adobe

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icurate2005Author

Known Participant

LR version is 15.1.1.

Original files are DNG with small preview.

I’m adding a screenshot of my export settings which are what I use for all of our archived images.

Mac OS 15.7.4

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