Quality Difference in HDR AVIF Exports between iPadOS & iOS seen in Apple Photos

Report · Feb 07, 2024

Expected behavior:

Whether exported from Lightroom on iPhone/iOS or iPadOS: Images in Lightroom mobile enabled for HDR editing exported as HDR AVIFs should display the same when viewed in HDR in other software. HDR AVIFs exported on one device type should not have artifacts or issues that AVIFs from the other do not.

Observed behavior:

HDR AVIF files exported from Lightroom on iPad—using "Save Copy to Device," “Export," or “Share” to nearly any destination—can have noticeable issues compared to those exported from Lightroom on iPhone when both are viewed in HDR in Apple Photos on iPhone 12.

When viewed in Photos on iPhone, both devices’ Lightroom AVIF exports do render in HDR—this is not an issue with “does it show up in HDR.”

However, when displaying in HDR on the iPhone, the iPad-exported photos show luminance/color banding (I believe that's the right term)—ie, boundary lines between various luminance/color areas. This can be very subtle or extremely obvious, depending on the image, and obviously affects quality overall. These issues do not occur in the same photo exported from Lightroom on iPhone. There also seems to be some difference in overall color between the AVIFs Lightroom produces on the two devices.

When viewed on iPad, Photos does not display either AVIF in HDR. That’s expected behavior—the iPad screen is not XDR. The SDR fallback is identical between the two AVIFs, and does not have banding issues or quality differences. Also expected, and good.

However, different unexpected display behavior does occur in one place when using iPad: The thumbnails of iPad-produced AVIFs in the Photos grid view are overly bright/blown out compared to the iPhone-produced AVIFs. When looking at the Photos grid view on iPhone, you do not see this issue.

Steps taken to reproduce (details on hardware/software, screenshots further below):

- On both iPad and iPhone, take exact same Lightroom version of same photo with HDR edit mode enabled, and export from Lightroom using "Save copy to device." Settings: AVIF, largest available dimensions, quality 100% (also tested at 90%, same issue), no watermark, HDR Output turned on; all metadata included; file naming original; no output sharpening; color space Rec. 2020.

- Allow Photos in iCloud to sync iPad-exported photo to cloud library. View both images on HDR-capable iPhone in Apple Photos, opening the photo and giving time to let screen adjust to display full HDR. Color/luminance banding appears on the iPad-generated AVIF, but not the iPhone-generated AVIF.

- Separately, go to Apple Photos on iPad and view both thumbnails to see noted distortion/difference in brightness there between the iPhone and iPad-produced AVIFs.

Visibility of issues in Photos on iPad exports varies widely depending on the photo, but something is noticeable on every image I've tested. Sometimes it's obvious, sometimes I have to really look for it. The distortion does not always occur in actual brighter-than-normal “HDR areas” within the image.

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This is not just an issue with the specific steps noted above. Nearly any other Lightroom export path on iPad produces an AVIF with the same issues compared to export on iPhone. For example:

- I have tried to isolate if AVIF transfer over iCloud Photos itself is the issue. I used a MBP to get both AVIFs out of iCloud Photos, and put copies back into Photos on the MBP before then viewing on iPhone. So, both AVIFs are coming to the iPhone over iCloud Photos in this scenario. The iPad-exported image issues/difference persisted, and the iPhone-exported image was fine.

- A few other Apple apps beyond Photos will display an AVIF in HDR on the iPhone (e.g. Files and Mail). I tested those, too: I tried exporting to Files from Lightroom on iPad, syncing via iCloud Drive, and then viewing directly in Files on iPhone. I have also tried exporting and sharing as an email attachment (making sure it stays as AVIF) and viewed on iPhone.

All of these tests still showed the Lightroom on iPad-produced AVIF displaying in HDR in Photos/the Apple software with issues that the Lightroom on iPhone-produced image did not show.

Notably: If I reimport the two devices' HDR AVIF exports back into Lightroom, Lightroom will display them the same/without issue. But it seems like something's off with Lightroom's export if other software is displaying the two differently.

Screenshots

Especially since the issues crop up outside of HDR brightness areas, I’ve been able to produce a couple. After taking the screenshots, I dialed the brightness down and messed with the contrast to help show the banding issue and color differences, which is why they look so dark/awful. Brightness/contrast adjustments were exactly the same in Photoshop for the comparative screenshots. The first two were both taken on iPhone; the second on iPad. These are crops, obviously.

Lightroom on iPhone AVIF export, viewed in Photos on iPhone (good/expected):

Lightroom on iPad AVIF export, viewed in Photos on iPhone (artifacts/banding/altered color):

Same two AVIFs viewed on iPad in Photos in grid/thumbnail view. iPad AVIF export on right. No brightness or contrast adjustment, just the (overly tight) crop:

Known Workarounds:

1) "Save copy to device" on iPhone is the obvious and easiest, and what I'm doing for now!

2) I have found that two very specific routes on iPad that result in an apparently issue-free HDR AVIF that originated with Lightroom on the iPad. Other permutations of these haven't worked, just this exactly:

- Either Export the AVIF to the MBP via direct Lightroom Export > AirDrop AVIF to MBP. Or Lightroom Export > email attachment as AVIF > save attachment out of Mail direct to disk on MBP via right-clicking on image in Mail.app and choosing "save attachment."

- Then, import that resulting file directly into Photos on the MBP. Sync via iCloud Photos to view on iPhone in Photos.

- The banding issues will have disappeared.

3) Weird: Rotate the iPad-generated image 90 degrees in Photos’ native editor on iPhone, save changes, and then edit and rotate again the remaining 270 to get back to normal orientation. This... weirdly, works, even after the first 90 degrees. (if you choose to revert the edits, it goes back to the problematic version.)

After you do #3, Photos spits out both an HEIC and AVIF when you export the image out of Photos in a certain way. So, I suspect Apple is automatically creating an HEIC for display purposes when the AVIF is edited (Apple AVIF support is read-only), and something about that conversion fixes the issue. I thus also suspect they're doing some sort of similar unbidden conversion on the back end somewhere in route #2, though do not have specific evidence for this. Obviously, uncontrolled conversion to HEIC isn't a great thing—it's lossy, you can't control quality, etc.

Apple's problem, not Lightroom?

I realize that Apple AVIF support in Photos/other iOS apps, particularly HDR, is imperfect. At minimum, I have seen that Photos doesn't necessarily handle color-specific tone curves exactly as Lightroom does. But it's not nonexistent—it does support HDR AVIF display on the right screens. And even if what's displayed is imperfect/doesn't quite match what we see in Lightroom, AVIFs coming from Lightroom on iPad shouldn’t display markedly worse than those coming from Lightroom on iPhone.

Based on my testing, I believe this is a Lightroom/Adobe bug with how it is exporting HDR AVIFs on iPad. Something in the Lightroom iPad HDR AVIFs that Adobe's implementation doesn't have a problem with—since it can re-import into Lightroom without seeing issues—but Apple's software trips up on.

But, fully a possibility there's an issue on Apple’s end that I am not pinpointing! Or, possibly incomplete Apple's implementation of AVIF rendering. Still notable that it only happens from the Lightroom iPad export, though, so, that's why I'm posting this as a bug here to start.

Hardware/software:

- iPhone 12 running iOS v17.3, Lightroom v9.1.1; iPad Pro 11" (second generation), running iPadOS v17.3, Lightroom v9.1.1. Also using 13" M1 2020 MacBook Pro running MacOS v14.3, Lightroom v7.1.2, for some file transfer and comparison.

- The iPhone 12 will display AVIFs in HDR in Apple Photos, select other Apple software like Files and Mail, and Lightroom (up to 3 stops in Lightroom). iPad and MBP will revert to SDR in Photos, but will display up to 1 stop of HDR in Lightroom.

- True Tone, Night Shift, and auto-adjusted brightness all turned off for testing. Brightness set around halfway on all devices, and at exactly the same brightness level when making comparisons on same device. I am always working with original images, not smart previews.

- Tested exports from images taken from multiple iPhone generations. Tested on photos explicitly restricted to 1 stop of HDR in Lightroom and photos without HDR stop restriction with HDR content into 2 or 3 stops. Tested with originals in HEIC, DNG, and enhanced (denoise) DNG formats.

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Finally, there is no corresponding "save copy to device" on MacOS. That is the export feature where I first noticed this, and my preferred export method on mobile, so I did not test much with Lightroom-produced HDR AVIFs from desktop Lightroom. I also didn't test JXL extensively, as Apple JXL support is terrible, but one Lightroom export in JXL confirmed the same basic issue when viewed in Photos.

I also haven't dug for other software that will properly render HDR AVIFs on iOS to compare, at this point.

Not comfortable posting originals or the full AVIF exports for privacy reasons on here, but happy to share directly with Adobe reps if desired.

Report · Jun 17, 2024

Thank you for your bug report, I've been suffering from the same bug.

On my side, it's not really relevant if it's exported from iPad (iPad Pro M4 -- with HDR display) or iPhone (iPhone 14 Pro).

It displays initially good in the Photos app when exported with color space Rec. 2020.

Then just kill the Photos app and restart it, or see the photo on a sync'd device, and it's washed out.

Workaround #3 mentioned by you fixes it temporarily, which definitely reinforces the feeling it's a Photos app.

Apple is supposed to support ISO HDR, are Lightroom exported photos following this norm?

Could somebody try with iOS 18 Beta if it fixes it?

Report · Jun 17, 2024

I've upgraded to iPadOS 18 DP1; everything else is just the latest full release of the OS and Lightroom. That doesn't seem to have made a difference in my flow issues described above. But re iOS/iPadOS 18... honestly, it's a developer preview—I'm not expecting it to have every fix or change in it by any means! (I'm not going to stick it on my iPhone; too unstable.)

Interestingly, I have not had the issue with iPhone-exported images looking good—and then "breaking" and looking washed out, that you describe.

One new data point: I have found that an AVIF exported from LrC or LrD and then imported into Photos on MacOS will display even worse (color shifted, a mess) on the iPhone HDR screen. Photos does still think it's an AVIF and displays it "in HDR" (brightens the screen) on the iPhone. It just looks terrible—color shift, etc. So, is Apple treating the AVIFs differently depending on where they come into Photos? I'm not sure it's that simple.

My initial testing in my first post indicated that a LrM iPhone-produced AVIF could import fine into Photos on MacOS, but the iPad-produced one would still look worse. That kind of points at Adobe producing slightly different AVIFs.

But, as I just noted, LrD/LrC-produced AVIFs "break" if they go into Photos on the Mac. Weirdly... they are fine if I AirDrop them to the iPhone, and they go into Photos that way! That kind of points at Apple handling AVIFs differently in Photos depending on the file + import device/OS.

Here's my new trick, based on the newest testing: Export on desktop (LrC or LrD); then, AirDrop the AVIFs to my iPhone and get it into Photos that way. Then, I'm fine. It also solves the issue of sometimes having only a smart preview in the cloud. I would be curious if this fixes your issue of Photos displaying it properly once but then not a second time.

Basically, for me, as long as it is exported from Lightroom on the iPhone LrM, or LrD/LrC, and enters Photos on the iPhone, I'm definitely good. Otherwise, likely trouble.

It's just really hard to sort out whether the AVIFs are getting produced to a slightly different standard on the different Lightroom platforms, if Apple's support is spotty, or... both. Based on my testing, it seems like both, to some extent, but... I don't know who's really breaking whatever standard. I think the conclusion remains "it's a messy landscape right now" more than anything, unfortunately.

My hope is honestly that Apple starts playing nice with Adobe's JPG+gain map export format in the final iOS 18 release. It takes tone curve remapping to make HDR AVIFs (HDR-only, no gain map) look OK on non-HDR screens. Chrome on MacOS does actually seem to do it, but, I don't know if there's even a standard at this point for handling it. The JPG+gain map system is much more backwards compatible, and it'd be nice to have that in place while AVIF gets figured out...