Photos for Mac removes wrong duplicates

I have just tested this in the current version of macOS Sonoma, with the same result.

For two JPEGs with the same pixel size but a different amount of JPEG compression, Photos is keeping frequently the higher compressed version with a smaller file size, usually a saved, adjusted version. In the case where I tested this, the keeper has been the newer version, so the adjusted version has been kept, not the original. And on all the keepers the exif tag "Lens ID" has been missing - very annoying to see "No Lens" in the info for a photo in Photos, also the "Keeper" had no caption and a different title. For example:

The info of the less compressed, removed version:

Have you filed a bug report? You could use the feedback link posted by Richard Feedback - Photos - Apple,

or, if you have a developer account or are participating in a beta software forum and have access to the Feedback Assistant, use the Feedback Assistant. The feedback Assistant will allow you to add screenshots and test data and logs.

It would already help a lot, if the Duplicates album would highlight the versions, that Photos has picked as keepers. so we can see, what will be kept, before we merge the photos.

I haven't found that to be true, but then I'm not sure you mean by resolution-- resolution is measured in pixels or pixels per cm, not megabytes or kilobytes. It's possible (though not likely in this extreme) that a 200 KB picture has a higher resolution than a 3 MB one. The size of a file in bytes reflects the level of compression. When a picture has lots of sky, for instance, where it all looks pretty much the same, then the file can be made to be much smaller with little or no loss of information. Are you sure that Photos is picking the one with fewer pixels?

I do wish that Photos separated Exact matches from Similar matches. In fact, I'm going here:

Feedback - Photos - Apple

right now and making that suggestion. I can't believe I haven't done it, before.

Oddly, I just tried this, and if one of the Exacts is a favorite and the other not, it marks them both favorite, and the deleted one may not be the one that was originally favorite. Hmm.

We are lucky that the eliminated duplicates go to Recently Deleted, so we have a month to check for mistakes.

Double check on the pixels thing and get back to us...

léonie wrote: It's true, ... Photos has been keeping the Jpeg with .... the higher lossy compression rate.

That's crazy-- I'm again off to the feedback site:

Feedback - Photos - Apple

In Merging two jpegs with the same resolution but differing in compression loss, the smaller, more lossy image is saved, and the better, less lossy image is discarded.

Jamie Crain wrote: Thanks. In my case the larger file would be the original so I’m fairly sure that would have the higher resolution.

Here are two pictures of a cow being bathed at the fair:

The left one is the original, and the right one is a duplicate.

The left, original picture has a file size of 1.5MB. The right one has a file size of 3.2MB. They both are 4032x3024 pixels. The difference is the compression, not the quality of the picture.

This one

is 3629x2722 and its file size is 6.5 MB.

Aristotle was "fairly sure" that heavy things fell faster than lighter ones-- but he didn't check.

Very Interesting dilemma I am wondering if Apple has replied to anyone on this topic on correcting or clarifying this situation. I am holding on deleting or merging any photos until I get a better picture. PTP.

It's true, I just tested again. For all JPEGs I merged (the same resolution), Photos has been keeping the Jpeg with the smaller file size - the one with the higher lossy compression rate. That is definitely not the photo with the higher quality.

I am finding the Duplicates album useful for detecting duplicates, but I am always selecting the "keeper" manually. I am mostly having similar duplicates, not identical files, and then I want to be the judge which of the similar photos is the artistically better version.

Richard, it might be that Photos is keeping the most recently imported version. In all cases, where Photos has chosen the file with the smaller file size, the date of import has been the most recent date.

And I wil also send my feedback again.

I am always picking the "keepers" manually. Even if the original files are identical, the metadata might differ - different titles or keywords. I am always looking at the photos enlarged to compare the adjustments, then compare the Info, and instead of clicking "merge" I am always deleting the file I want to be removed. Most o the exact duplicates are duplicates I created intentionally, because I need them twice in the same album for a slideshow or in different albums with different dates.

How are you importing your photos? Have you been importing photos by syncing your devices with iCloud or manually with iTunes or the Finder?

Are you importing from a digital camera or from an iPhone or iPad?

Most of the duplicates in my Library have been created along time ago by My Photo Stream.