I think Photos may reprocess JPG files to a certain quality (85?). The originals are buried in there I think, But Photos does it’s own interpretation for it’s use. So if you drag a file out of Photos, You may be dragging the reprocessed version out of the program. That is my working theory. You can try exporting the “original” out and see if it is bigger, or go through the back door with the “Show Package Contents” command on the library and then dig the original out of the Masters folder for comparison. It could also be the Block size issue that Karen mentioned, but only if you are using two different drives that have different block sizes when comparing.
I am downloading my conference photos from my iPhone to my desktop. I use "Image Capture" with a hardwire USB cable. About half way through the 600 photos, it froze.
After four tech support folks, trying to get the rest to download, the final tech person suggested I turn OFF iCloud syncing, and pull them to my computer from Photos application. all the photos were there, and I clicked and dragged the half that I was missing.
Apparently they were already uploaded to Photos application on my desktop computer because ICloud was turned on on both my iPhone and the desktop. Now, I've been told that Photos reduces the sizes of all images to small JPEGS. That would be horrible because I want the highest resolution that the photos were originally taken. So, that's why I use Image Capture. I want them on my computer, not the Photos, nor the Cloud, or anywhere else but my computer in a designated file.
Now I CAN upload the photos from my iPhone to Image Capture, because it is not incumbered by ICloud. NOW I notice that the images for both JPEGS and .MOV, are smaller once they were dragged and dropped to my computer from Photos application. The tech folks said they would not be reduced, that Apple had fixed that, or changed that, etc. I had something clicked with a blue check mark to "keep originals" the same size.
Now a 30.5MB .MOV file from Image Capture is shown as a 18.3MB .mov file when I drag it from Photos.
A JPEG file at 9.3MB from Image Capture is shown as a 6.2MB file when dragged from Photos. Photoshop says they are the same size and ppi.
So any other ideas on why they are reduced coming through Photos? What gives?
Many thanks in advance.