[jcdoss]

A quick question... I know that Lightroom edits never change the raw file, but does LR ever make any kind of changes to the raw file at all? exif? keywording? all that extra stuff is stored in the catalog and not in the file, right? I'm just trying to figure out why my cloud backup system has decided to continuously upload stuff two and three times.

[stevebrot]

Here is a quick answer (7 minutes later and counting...)

Yes, LR can and will write metadata to imported DNG files if one is configured that way or if one makes an explicit request to do so or if one uses plugins that do so. I don't have the specifics at hand as I type, but will be back in a bit with more info.


Steve

[Paul the Sunman]

There is an option in the catalog preferences to allow LR to save time changes to the raw file, but by default it's off. Otherwise, it shouldn't change the file.

Another possibility is that you're writing XMP sidecar files: are there any sitting beside your raw files? See Catalog Settings > Metadata. Unless you are sharing raw with someone else who needs to access your edits, I recommend turning that off.

However, have you checked the modification date of some of the files? Do they show changes after accessing with LR? I don't on my system (mac).

[jcdoss]

However, have you checked the modification date of some of the files? Do they show changes after accessing with LR?

Good one. The answer is yes. This means since I'm using Amazon to store a second set of backups in the cloud, and since Amazon won't let me sync my photos to the cloud from a NAS where I store most of my stuff locally, then it will continuously upload new copies every time the raw file changes. This might not be a big deal, since I don't go around modifying exif data all the time (usually once on import) but I do sometimes add new keywords from time to time as they occur to me. I'll have to check/see if its the keywording that is changing the mod date.

[Glen]

This would be pretty important for forensic work where there cannot be any change to the file what-so-ever. This wasn't my question but I was just thinking on my keypad and seem to recall hearing this somewhere.

[West Penn]

If you are using DNG raw files, you're likely getting two copies stored because Lightroom adds/stores whatever modifications you've made to the image back into the DNG file. You still have the original DNG and a second DNG with the modifications (exposure, highlights, shadows, vibrance, etc) that you've made in post processing. At least this is what happens to me when using a portable hard drive that automatically adds new files to the hard drive. I guess this is how the cloud works as well. If you're using sidecar files, you should have just the original raw file, together with a sidecar file containing the modifications made in post processing.

[lsimpkins]

A quick question... I know that Lightroom edits never change the raw file, but does LR ever make any kind of changes to the raw file at all? exif? keywording? all that extra stuff is stored in the catalog and not in the file, right? I'm just trying to figure out why my cloud backup system has decided to continuously upload stuff two and three times.

I believe that the answer to this question depends upon whether you are using PEF or DNG raw formats for your images and how you have set the LR option "Automatically write changes into XMP".

In the case of using PEF, changes are written to the catalog or both the Catalog and the XMP file if you have that option selected. I do not believe that the original PEF file is altered.

In the case of DNG files (with which I am more familiar) changes are similarly written to the Catalog if the XMP option is not selected. When it is selected, the changes are written to the Catalog and the XMP portion of the DNG file (which acts somewhat like a container for various information in addition to the raw data). The raw image data is not altered in either case, but the file size and file date may change.

As far as dates are concerned, I see at least three dates in my Library Module for each image: Date Time Original, Date Time Digitized, and simply Date Time (which I believe is when you last changed anything on the image). So, unless you can pin down the Date Time info used by the cloud storage system, you may not be able to control it in the manner you wish.

[jcdoss]

In the case of DNG files (with which I am more familiar) changes are similarly written to the Catalog if the XMP option is not selected. When it is selected, the changes are written to the Catalog and the XMP portion of the DNG file (which acts somewhat like a container for various information in addition to the raw data). The raw image data is not altered in either case, but the file size and file date may change.

I am using DNGs and my "Automatically write changes into XMP" box is checked.
I don't recall checking the box, was it checked by default?
Other than causing hassles with my cloud storage system, what advantages/disadvantages are there for having the XMP box checked?

Thanks for your input!

[Gimbal]

Some argue that any writing to a raw file is a bad idea so therefore you should use a sidecar file. If the computer crashes while writing it’s better to get a corrupt xmp file instead of a corrupt raw file.

Also a sidecar file might help if you decide to use something else then Lightroom in the future.

Or so I’ve heard…

[stevebrot]

Some argue that any writing to a raw file is a bad idea so therefore you should use a sidecar file. If the computer crashes while writing it’s better to get a corrupt xmp file instead of a corrupt raw file.

Also a sidecar file might help if you decide to use something else then Lightroom in the future.

Or so I’ve heard…

Unfortunately, most of the XMP (sidecar file or not) is Adobe-specific and chances are poor that future tools will properly replicate the effect of those settings.


Steve

[stevebrot]

but will be back in a bit with more info.

...at least that was my intent. I had a nice write-up composed, but the PF firewall locked me out for a day when I tried to post it. In the mean time, the gist was contributed by other users. The subject ends up being fairly complex when considered in depth such that Martin Evening, in my copy of his Lightroom book, devotes a full eight pages of detailed text to the matter. It is probably enough to simply disable the setting and remember that one never "saves" a file in Lightroom and that there is no need to write or sync-up metadata with the feature turned off.


Steve

[jcdoss]

It is probably enough to simply disable the setting and remember that one never "saves" a file in Lightroom and that there is no need to write or sync-up metadata with the feature turned off.

This was what I learned after reading for a while. It is a more of a complex problem than I or many of the people responding to posts/articles online had expected, which makes me feel a bit less like a moron. I've opted to UNcheck that box, save all DNG file edits and keywords in the catalog and not with the individual files, and keep them as raw as they can be from now on so no more churning and re-uploading to the cloud.

Thanks for your help everybody!

[lsimpkins]

I am using DNGs and my "Automatically write changes into XMP" box is checked.
I don't recall checking the box, was it checked by default?

I really don't recall if that is the default or not.

Other than causing hassles with my cloud storage system, what advantages/disadvantages are there for having the XMP box checked?

Thanks for your input!

I like to have everything related to an image contained in the DNG file itself as well as the Catalog, just as a sort of belt and suspenders approach. I do create XMP files whenever I am working with native raw files from my wife's Panasonic camera and my cell phone.

In addition, I have found that on my Win 10 installation, Windows Photo Viewer (NOT Photos) does display my DNG images as adjusted in LR. I don't think WPV is using the LR Catalog, but reading at least some of the XMP-like information embedded in the DNG. This may be a minor convenience, but occasionally helpful, at least to me.

As far as software migrations are concerned, On1 Photo Raw uses your catalog data to make the same adjustments to your images if you migrate to that program. So in this case, too, writing XMP-like data to the actual DNG file has no real advantage.

I feel it really comes down to your own workflow preferences and in your case the option probably creates more hassle than you need.

[stevebrot]

In addition, I have found that on my Win 10 installation, Windows Photo Viewer (NOT Photos) does display my DNG images as adjusted in LR.

Well, this is interesting! Apparently LR inserts new preview JPEGs as well as the XMP. (WPV does not do RAW processing, but is capable of extracting preview JPEGs from EXIF.)


Steve

[stevebrot]

As far as software migrations are concerned, On1 Photo Raw uses your catalog data to make the same adjustments to your images if you migrate to that program.

Has anyone here on PF actually done a comparison of results post-migration? I am not saying it isn't so, only that the XMP changes a lot, version to version for LR and ACR and that there are a lot of develop settings and interactions to replicate.


Steve