Two versions of SAME PHOTO have DIFFERENT SIZE

Question

Level 1

12 points

Two versions of SAME PHOTO have DIFFERENT SIZE

I am going through my Photos library with PhotoSweeper, looking for duplicates (using the "Similar Photos" feature), and have come across a real head-scratcher. In particular, I find many duplicates that are pretty much identical but for one detail: one is a few times bigger (size in MB-wise) than the other.

Some context: My Photos library is a bit of a mongrel, concatenated over years by (a) migrating from iPhoto, (b) manually importing pictures, (c) direct saves from iPhone etc. Now, I am trying to consolidate all pictures in the single library (thank you, "store on iCloud"), and as I do that I am trying to (a) delete duplicates while (b) making sure I retain meaningfully different photos.

Issue: Here's the issue - I have identified many pictures that appear pretty much identical, but have different sizes. Identical how? Here are the attributes I have verified are the same:

visually (same moment)
time taken
dimensions
file type (JPEG image)
color space
...and many, many more pieces of meta data

However, when I look at the pictures' Info in Photos I find that one is, for example, 1.5MB, while the other version is 5.0MB (see screenshot below)

It gets weirder (hint at the cause of the problem?) One of the first things I did is tried to go beyond Photos and look at the files themselves. I did this in two ways, and got different results, which may hint at what's going on:

If I export the two photos using Photos' File > Export feature, the resulting two files have the same (larger) size
BUT, if I just drag the two images out of Photos and into a folder, the resulting tow files have different sizes, with the smaller one having a .jpg extension, while the larger one has a .jpeg extension (see screenshot below)

Does anyone have any idea what may be going on? Does my library have some sort of issue that Photos 7.0 (my version) somehow does not recognize/compensate for? Does Mac OS X somehow underestimate the size of .jpg files, and this issues feeds into Photos? Or am I misunderstanding some fundamental difference between the otherwise identical photos?

Happy to share more info, even the files themselves - this is driving me nuts!

MacBook Pro 13″, macOS 10.12

Posted on Mar 28, 2022 4:49 PM

Reply

Answer 1

Top-ranking reply

Yer_Man

Level 10

164,016 points

Mar 28, 2022 11:28 PM in response to kwozniak

If I export the two photos using Photos' File > Export feature, the resulting two files have the same (larger) size

The resulting file size if you use the Export feature depends entirely on the export settings used. In particular the Quality settings, which determines the amount of compression used

BUT, if I just drag the two images out of Photos and into a folder, the resulting tow files have different sizes, with the smaller one having a .jpg extension, while the larger one has a .jpeg extension (see screenshot below)

Drag and drop simply gets the Preview of the image. When you edit an image Photos makes a preview of it for sharing to emilas etc, which saves you the chore of exporting. The preview is simply a *good-enough-for-most-things* version of the image.

So, want to do a quick version for emailing to grandma, that's the preview. Want a high quality version for subsequent re-editing? That's exporting.

In other words, this is all normal.

Reply

Answer 2

léonie

Level 10

197,655 points

Mar 29, 2022 1:29 AM in response to kwozniak

Photos that have adjustments applied or are coming from different sources may have different preview image sizes. When you migrate an iPhoto Library to Photos, the adjustments will be migrated burned i in as a Jpeg. Edited versions created by Photos may have a different quality, particularly, if you are using optimise storage with iCloud. When in doubt, revert the photo to the original to compare the original quality.

Reply

Answer 3

kwozniak Author

Level 1

12 points

Mar 29, 2022 6:53 AM in response to Yer_Man

Yer_Man, this is EXTREMELY helpful. I am a long-time and reasonably informed Mac user, and the fact that dragging pictures out of Photos results in lower size/quality is something I did not know. I will now, thanks! (FWIW, there Apple should really put a quick message every time you do this, something like "exported a preview version of the photo", or something like that; it's not like you expect quality loss when you drag files around between folders in Finder!)

I have one follow-up question - in my case, do you think it's reasonable to assume that my mongrel Photos library somehow contains both full-quality photos as well as these preview versions, side-by-side? Based on what I learned from you, my principle for eliminating duplicates will be to make every effort to eliminate the preview photos (otherwise identical, including resolution, but smaller size in MB) and keep the full-quality ones.

Reply

Answer 4

Yer_Man

Level 10

164,016 points

Mar 29, 2022 10:33 AM in response to kwozniak

You should not be seeing previews of the same photo alongside the original in the library Window. This suggests to em that at some point in the past an iPhoto Library was imported into another one, or something similar. And yes, keep the largest file size always.

Reply

Two versions of SAME PHOTO have DIFFERENT SIZE

Similar questions