Mojave Preview Export HEIC Lossless Slider

Question

Mojave Preview Export HEIC Lossless Slider

I have searched high and low to find an explanation of the Preview > Export slider shown below.

If I open a HEIC picture from a iPhone (no conversion) the slider is positioned as shown below and the file size is ~1>2 MB.

If I save the picture still as HEIC but pull the slider full right the file size goes to ~6>7 MB but does not appear to be any different.

With JPG the difference in the lossless slider was evident.

But what does the slider do with the HEIC format?

Posted on Dec 27, 2018 6:01 PM

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Answer 1

Dec 28, 2018 5:53 AM in response to VikingOSX

Thanks for the link. It does get very complicated.

https://developer.apple.com/documentation/photokit

Just in case anyone else is looking at quickly cropping / cutting a bunch of HEIC pics and wondering about the "Quality Setting", I ran a few more tests and the default (shown above) seems to approximately maintain the original capture file size (slightly larger).

Having said that, adjusting it a notch or two either way seems to have little discernible effect to my eye on print/screen/video. Perhaps in extreme zoom situations with high detail some artifacts show but in everyday rush work the default is fast, small and close to original.

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Answer 2

VikingOSX

Level 10

123,374 points

Dec 27, 2018 6:08 PM in response to SirLoungeAlot

Aside from a bunch of people guessing, the real reason/benefit may remain a secret with the Apple Preview development team. They by the way, and other Apple product teams do not participate here, and as fellow users, we simply may not know the precise benefit of this slider beyond its scale.

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Answer 3

VikingOSX

Level 10

123,374 points

Dec 27, 2018 6:25 PM in response to VikingOSX

Here is a Dec. 27, 2018 Lifewire article on HEIC/HEIF formats.

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Mojave Preview Export HEIC Lossless Slider

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