Exporting an image as JPG at less than full size is very blurry

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Exporting an image as JPG at less than full size is very blurry

I use Photos app on Mac to crop and enhance HEIC files and export as JPEGs for social media scheduling tools which don't accept HEIC (mainly Facebook and Instagram Business Suite).

The goal is to have a JPG image, light in weight, to avoid FB/IG compression to kick-in and do even worse.

The problem is the following: If I export the files as Large or Medium, regardless of the quality settings, they look very blurry and are horrible.

Why?

Workarounds found so far:

Use Photo App and export the photo with the settings "Full size" and quality "Low". This is the only way to have a sharp image. The downside is that sometime is the image weight (big enough to trigger FB/Instagram compression).
Use an automator script which converts the HEIC to JPG (the JPG outcome is stunning), with the downside that I can't work on enhancing the photo

I really don't understand what's the problem and why Apple hasn't fixed it in years: there was another post for the same issue in Feb 2018 and the bug is still here.

MacBook Pro 14″, macOS 13.3

Posted on May 20, 2023 6:40 PM

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Answer 1

May 24, 2023 7:32 AM in response to pontix

"full size with low resolution" is not a choice.

Size, in this case, is equivalent to resolution. For the four pictures I used, the exported heights were 2032, 1280, 640, and 320 pixels. (The uploaded segments were smaller-- the first only 400 pixels.) If you compare them at the same physical height like an inch, as I did (depends on you monitor), then the first has a resolution of 400 dpi and the last is 60 dpi. Size is the same as resolution.

Quality is about jpeg compression-- the amount of loss of information allowed to make a smaller image but one that is similar to the eye. This depends on the sort of image you have. If its a picture of blue sky, the a great deal of compression will result in a picture that looks pretty much like the original. If the picture has lots of fine detail, then it will suffer more from compression.

The are two very different ways to make a smaller file. Sometimes lower resolution doesn't look so good; sometimes more compression doesn't look so good. Intuition may not be very reliable, here.

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Answer 2

May 21, 2023 8:18 AM in response to pontix

These are screenshots of sections of a picture that I exported at the four sizes, Full, Large, Medium, and Small:

The "small" image is obviously low resolution, but I don't think I'm getting the same results you are. Large and Medium both seem acceptable for viewing on a computer screen.

How are you doing the export? I used the menu selection "File>Export>Export 1 Photo." I had the dialog set like this