Help- Artifacts/Corruption in several Photos

That is a very convincing test result!

So it is not the HEIC format per se, and not the transfer to the Mac, but the processing of HEIC images on the Mac in normal boot mode. None of my three Macs is showing such periodic artifacts on the HEIC images in Photos.

So I have few Macs too, but too old to run Mojave, a 27"iMac mid 2010 with 10.13 (High Siera) does NOT exhibit this issue.

Maybe it points to HW, but I am tempted to run one last arduous test where I restore High Siera on my current iMac... (unsure if I can go back from Mojave from a High Siera time machine backup!)

The good thing, for those of us with that issue, we can switch to JPG on iPhone and all is well at the expense of more storage consumption on the iPhone. I've update the bug report, maybe one day Apple will respond.

we can switch to JPG on iPhone and all is well at the expense of more storage consumption on the iPhon

And at the expense of more storage consumption on the Mac. I have converted most of my image files on my Mac to HEIC and are storing the originals on external drives. This way I can keep 50000 photos in my iCloud Photo Library without having to revert to Optimize Storage on the iPhone. I like HEIC. It does not only save storage, it also saves bandwidth when transferring the files between devices.

We have very close hardware, interesting. As per your previous post, I also would like to believe it’s related to Mojave, doesn’t explain why @leonie doesn’t have the Issue and many other iMac users. Maybe tomorrow, I’ll revert back to HighSiera and check!

Oh! I was under the impression you were using Mojave, so that’s two differences with our setup, different graphic card and OS. I think now I will revert my iMac to High Sierra.

IF the artifacts do NOT appear with 10.13 I am inclined to deduce that it’s a software implementation issue, maybe driver issue that could implement hardware based acceleration or optimizing for HEIF core encoding/decoding functions... and not a hardware graphics card issue.

I think at this stage it’s fair to say that there is an issue with displaying/previewing/editing HEIC photos on certain subset of iMac GPU on Mojave. (GeForce GT family?)

Those of us on Mojave/GPU “bad combination” can fall back to JPG until hopefully Apple investigates further and hopefully fixes something.

I do not think it’s a widespread issue across all iMac GPUs because there would have been much more roar!

But I'm not sure what's the best solution for the many hundreds of heic images accumulated on Photos before my recent upgrade to Mojave, and before I realized the issue.

The alternative would be to keep the iPhone shooting HEIC/HEVC, but to download the photos using a USB connection and have them converted to JPEG during the transfer to the Mac.

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.

You can change this import behavior in iOS 11. Go to Settings > Photos. In the "Transfer to Mac or PC" section, tap Keep Originals to prevent the media from being converted when importing.

As to your existing photos, you can use the online converter to convert HEIC to JPG. The online conversion will hopefully not be showing the same glitches as the local conversion on your iMac: https://heictojpg.com

Thanks for posting. Actually all we did is find root cause and a workaround, the fix is what is key. It would be great if more would open a bug report with Apple or at least through their feedback site.

I have opened a bug report a week ago and it has not been reviewed.

Thanks. My workflow is to gather images from my iPhone into Photos via iCloud. This works best right now for a variety of reasons. If I then try to plug in my iPhone to download images (even if I take the iMac offline), Photos gets confused and I end up with duplicates when the cloud gathered images subsequently make their way into Photos. So it's simplest not to connect -- at least until Photos/iCloud prove to me that they can handle both approaches. Much easier to give up on HEIC at the moment. My big problem is the 1000 or so HEIC images currently in Photos that I cannot edit and disperse as I normally do. I can export them as HEIC files and convert them to jpg in Preview without a problem, but this doesn't allow any editing in Photos. I haven't discovered an efficient workaround for this yet. I opened a report with Apple.

Really?

In a previous post you wrote

3- Boom, very good suggestion, I converted the clean JPG w Preview to HEIC and voila artifact ! Please see attached screenshot.

That made me very suspicious of using Preview to convert the HEICs to JPEG.

I can likewise confirm that I have no problem exporting HEIC images from Photos and converting them to JPG in Preview. This is not a very satisfactory workaround, however, because it precludes using any of the editing features of Photos. When I export edited HEIC images, Photos returns JPGs with artifacts. This issue arose after I upgraded to Mojave. Prior to that, I could export HEIC images edited in Photos as easily as JPGs.

And pulled my comment quoting yours 😁 at least you have a bug report that is active. Unsure why mine never got reviewed yet or even tagged as duplicate. Let’s hope it gets fixed sometime soon.

Update: it’s like they heard my thoughts, it is tagged as duplicate now!