My Mac cannot open or view files converted by LR from tiff to DNG

[camner]

Lightroom Version

12.1

Operating System

1. macOS 12 Monterey

I converted some TIFF files to DNG files from within Lightroom, and those files are not viewable either by using Preview or Quick Look. Files converted by light roll from CR3 to the DNG can be viewed by both Preview & Quick Look.

This is both puzzling and annoying.

Anyone aware of an external file viewer that would support viewing these converted files?

 

[Califdan]

If you are exporting a TIFF as a DNG, check this checkbox in the Export dialog.

If you're converting to DNG on import, the checkbox is in your preferences on the File Handling tab

I'[m not a Mac person but I think that will fix it.

 

[camner]

Thanks very much for your suggestion. Although I was pretty sure that I had "in bed fast low data" checked, I just ran a test again. No luck. :(

 

[johnrellis]

I observe the same bad behavior with Mac Preview, Quicklook, Quicktime, and Photos. Evidently, they all treat the DNG as a "raw" file (a mistaken assumption -- not all DNGs contain raw data, obviously).

I was able to view it with the Mac program XnView MP, also with the Windows programs Faststone and Irfanview.

 

[camner]

I observe the same bad behavior with Mac Preview, Quicklook, Quicktime, and Photos. Evidently, they all treat the DNG as a "raw" file (a mistaken assumption -- not all DNGs contain raw data, obviously).

I was able to view it with the Mac program XnView MP, also with the Windows programs Faststone and Irfanview.

I just download and looked at XnView MP, which was able to open a TIFF-->DNG file or viewing. However, it appears to be using the embedded small image (192 x 256 for an image in portrait mode) rather than looking at all the TIFF data in the DNG container. That makes it useful for getting a quick idea of what the image is, but it's too small to be useful beyond that.

 

[Johan Elzenga]

Maybe you should ask yourself why you would want to convert a tiff to dng in the first place. What do you think you will gain by that?

 

[johnrellis]

Hmm, I'm barely familiar with XnView, having got it just for my testing. But when I convert a TIFF to DNG in LR, view its thumbnail in XnView, do View > Preview > Real Size, then double-click the thumbnail, I see a full-size preview or a 1024 x 768 preview, depending on whether I selected Preview Size: Full Size or Medium Size in LR's Convert To DNG.

 

[camner]

Digging further, I saw that the box to convert to lossy DNG was checked. Experimenting further, I realized that with this box checked, no matter what preview size drop-down option is chosen, the longer edge of the embedded preview is always 256 pixels.

I suppose that this behavior could be a feature (minimize the size of resulting file) or a bug (the chosen drop-down size option is not respected). If it is intentional behavior, I think it would be better to have the size drop down grade out, because the weight is implementing a present, the user can make a choice for a full-size preview, but the choice is not respected when the user has chosen to create a lossy dng

 

[camner]

Maybe you should ask yourself why you would want to convert a tiff to dng in the first place. What do you think you will gain by that?

Well, I have modified my workflow for less important and more casual images to have them processed through an external app (cuts down my editing time). This is done by exporting to a tiff file, which balloons the file size significantly. Since it is highly likely that I will never edit any of these casual shots again, it seemed reasonable to convert the files to lossy dngs, which brings the file size back down to something similar to the original file out of the camera (they are typically heic files from an iPhone.). Although I believe in the mantra "file storage is cheap," I have my source files in my dropbox folder as a form of offsite storage of current versions, and I am getting closer to my 2 TB storage limit in dropbox. So, I thought this conversion to lossy dng was a cheap and easy way forward. As it turns out, though cheap, it may not be easy. I don't like the fact that I can't easily see a decent preview of a file outside of Lightroom.

 

[johnrellis]

Digging further, I saw that the box to convert to lossy DNG was checked. Experimenting further, I realized that with this box checked, no matter what preview size drop-down option is chosen, the longer edge of the embedded preview is always 256 pixels.

That's curious -- I don't observe that in my LR 12.1 / Mac OS 12.6.1. When I select Full Size and Use Lossy Compression on a TIFF:

the DNG has a full-size preview, which my Xnview displays.

I verified that whether or not Use Lossy Compression or Embed Fast Load Data is enabled, LR is embedding a pyramid of previews in the DNG, up to full size:

256 x 171
512 x 341
1024 x 683
2048 x 1365
5616 x 3744

$ exiftool -a -G1 -imagewidth -imageheight 20191219_092356.dng
[IFD0]          Image Width                     : 171
[SubIFD]        Image Width                     : 3744
[SubIFD1]       Image Width                     : 683
[SubIFD2]       Image Width                     : 3744
[SubIFD3]       Image Width                     : 1365
[SubIFD4]       Image Width                     : 341
[SubIFD5]       Image Width                     : 171
[IFD0]          Image Height                    : 256
[SubIFD]        Image Height                    : 5616
[SubIFD1]       Image Height                    : 1024
[SubIFD2]       Image Height                    : 5616
[SubIFD3]       Image Height                    : 2048
[SubIFD4]       Image Height                    : 512
[SubIFD5]       Image Height                    : 256

 

[camner]

That's curious -- I don't observe that in my LR 12.1 / Mac OS 12.6.1. When I select Full Size and Use Lossy Compression on a TIFF:

View attachment 20094

the DNG has a full-size preview, which my Xnview displays.

I verified that whether or not Use Lossy Compression or Embed Fast Load Data is enabled, LR is embedding a pyramid of previews in the DNG, up to full size:

256 x 171
512 x 341
1024 x 683
2048 x 1365
5616 x 3744

$ exiftool -a -G1 -imagewidth -imageheight 20191219_092356.dng
[IFD0]          Image Width                     : 171
[SubIFD]        Image Width                     : 3744
[SubIFD1]       Image Width                     : 683
[SubIFD2]       Image Width                     : 3744
[SubIFD3]       Image Width                     : 1365
[SubIFD4]       Image Width                     : 341
[SubIFD5]       Image Width                     : 171
[IFD0]          Image Height                    : 256
[SubIFD]        Image Height                    : 5616
[SubIFD1]       Image Height                    : 1024
[SubIFD2]       Image Height                    : 5616
[SubIFD3]       Image Height                    : 2048
[SubIFD4]       Image Height                    : 512
[SubIFD5]       Image Height                    : 256

 

[camner]

My apologies for the proceeding post… stupid operator error! The correct post follows the right below the quote from John Ellis' post:

That's curious -- I don't observe that in my LR 12.1 / Mac OS 12.6.1. When I select Full Size and Use Lossy Compression on a TIFF:

View attachment 20094

the DNG has a full-size preview, which my Xnview displays.

I verified that whether or not Use Lossy Compression or Embed Fast Load Data is enabled, LR is embedding a pyramid of previews in the DNG, up to full size:

256 x 171
512 x 341
1024 x 683
2048 x 1365
5616 x 3744

$ exiftool -a -G1 -imagewidth -imageheight 20191219_092356.dng
[IFD0]          Image Width                     : 171
[SubIFD]        Image Width                     : 3744
[SubIFD1]       Image Width                     : 683
[SubIFD2]       Image Width                     : 3744
[SubIFD3]       Image Width                     : 1365
[SubIFD4]       Image Width                     : 341
[SubIFD5]       Image Width                     : 171
[IFD0]          Image Height                    : 256
[SubIFD]        Image Height                    : 5616
[SubIFD1]       Image Height                    : 1024
[SubIFD2]       Image Height                    : 5616
[SubIFD3]       Image Height                    : 2048
[SubIFD4]       Image Height                    : 512
[SubIFD5]       Image Height                    : 256

Well, this is curious, indeed. I used exactly the same settings on my conversion to a dng.

Looking at the output from exiftool of an image, it appears at first glance that my photo also has a number of different preview sizes:

But now look at the screenshot from within XnView of the DNG file and the TIFF file from which it was created:

You can see that the image dimensions of the dng file are reported to be 192 x 256.

And now looking at a different part of XnView, where the image file in the dng is also shown to be 192 x 256:

And then finally, looking at the image itself within XnView with View set to real size:

One sees a small image with a lot of white space around it.

I don't really know what to make of this… John's image as well as mine have a number of preview sizes contained within it. But for me, XnView it's only picking up the smallest size. This suggests to me that there could be a setting someplace in XnView that controls this, but like John, I am completely new to the app and therefore I don't know my way around it.

 

[johnrellis]

Perhaps upload one of the problem DNGs to Dropbox, Google Drive, or similar and post the sharing link here. I can see what it looks like on my Mac.

 

[camner]

Perhaps upload one of the problem DNGs to Dropbox, Google Drive, or similar and post the sharing link here. I can see what it looks like on my Mac.

https://www.dropbox.com/s/tro0wkiwtv8k316/2021_05_21-IMG_0707-editRP8.dng?dl=0

Thanks.

 

[GregJ]

I have a better solution. Don't do it.

 

[johnrellis]

It's a bug in Xnview. Your sample opened full-size for me in Xnview:

But then I finally noticed what I should have checked up front: I was running version 0.98. When I downloaded the most recent version, it showed what you're seeing, a 192 x 256 image:

 

[camner]

@johnrellis -
Thanks for taking the time to look into this. I posted on the XnView forum, and the developer said it was a bug but she would correct in the next release.

 

[johnrellis]

Very good.