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There is a setting in the "Photos" menu of the settings app that allows you to change the way that photos are transferred from iOS devices.

The setting described above

When you choose "Automatic" then plug your phone into a Windows PC, all of your photos show up as .jpg files in Windows Explorer. They can then be copy/pasted to any other folder. When you choose "Keep Originals", all your photos show up as .HEIC files, and they are significantly smaller.

Comparison of how the files show up in Windows Explorer, demonstrating what is described above.

My question is, what's happening here? It can't possibly be the case that iOS is transcoding every single piece of media on your iPhone the second you plug it into a PC. Does iOS store two different versions of every single photo? Or does it transcode them during the transfer process, and somehow estimate what the file size will be in order to show them properly in an alias sort of way in Windows explorer as JPGs?

And furthermore, as far as quality loss is concerned in terms of compression, which file format is higher quality? Are they both "first generation"?

Thanks in advance.

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  • This help? support.apple.com/en-us/HT207022 Nov 30, 2021 at 21:06
  • "When you import HEIF or HEVC media from an attached iOS device to Photos, Image Capture, or a PC, the media might be converted to JPEG or H.264." Yes, that does help! Seems to suggest Apple converts the media, rather than capturing it both ways, meaning JPG is second-generation. Nov 30, 2021 at 22:34

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When you import these photos over USB as JPEGs they will be transcoded as they're transferred. This means that photos are not stored twice on the phone in two different formats, and they're also not all batch-converted as soon as you plug in the device.

In this particular case, you definitely want to download the .HEIC file. Even though it is smaller, it is actually the file format that the photo is stored in on the phone. If you choose to download as .JPEG then the quality is most probably worse (and never better) - even though the file size might be larger. Every transcode of a file to a lossy format (such as JPEG) comes with a loss of quality - therefore you want to avoid such transcodes for getting the best possible quality.

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  • This might depend on what you consider to be your ‘original’. If, for example, you take a portrait photo with fake bokeh, the bokeh is only in the jpg, not the HEIC
    – Tetsujin
    Dec 1, 2021 at 0:23
  • Original refers to the setting in the question, so if the original is in fact in JPEG it is transferred as such, and not in HEIC.
    – jksoegaard
    Dec 1, 2021 at 0:34
  • @Tetsujin That...is not accurate? If you take a photo with fake bokeh it would appear as such in both the JPG and the HEIC. The JPG is converted from the HEIC, so it cannot be the case that the JPG contains aspects not found in the HEIC.
    – Ezekiel
    Dec 1, 2021 at 4:46
  • Just tested, with both Auto & Keep Originals. In both cases the jpg has the 'portrait fake bokeh' & the HEIC doesn't. [Both formats show in the phone's list in Image Capture, & both appear instantly if I take a picture with the phone already conected.] Auto perhaps makes different decisions depending on whether it knows your OS is capable of using HEIC or not. I don't think it's built-into Windows, you have to install support separately. I found this, can't test - howtogeek.com/345504/…
    – Tetsujin
    Dec 1, 2021 at 14:08

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