Hello,
With the update from iOS 26 to iOS 27 I have noticed significant regressions and degraded performance when using the Vision Framework for OCR via 'VNRecognizeTextRequest'.
The degraded performance is only applicable to the .accurate model, the .fast model is identical between iOS 26 and iOS 27.
I have an app that uses this framework extensively for extracting information from the video feed of professional cinema cameras. This runs using en-US, language correction off with a specific region of interest.
On iOS 26 everything works reliably as it has for the past few years, with the exact same codebase on iOS 27 many strings that were previously detected are no longer detected, some strings return as if they've been read upside down (ISO1280 is returned as 08ZLOSI) and there are a lot of Cyrillic look alikes mixed into Latin text, there also appears to be a lot more junk characters tacked onto the end of numbers ('12ł' is returned when previously it was just '12'). You often see whole line duplicates too where the same text is recognised twice, once as a single line with all strings combined and once as individual strings.
The iOS 27 Simulator doesn't show any of this. I only saw it on real iPads, if you only test in the Simulator you'll miss it.
To put numbers on it, I built a test set of about 26,500 frame grabs and ran them through 'VNRecognizeTextRequest' on iPadOS 18, 26 and 27. With the version of my app that's on the App Store today, iOS 26 reads 99.7% of values correctly. On iOS 27 that drops to 65%.
I've resolved this issue now and have been able to retain the level of performance that existed on iOS 26, this involves various preprocessing steps to the images as well as a significant amount of validation after the Vision Framework returns its results.
These fixes took around 3.5 Days of work which is incredibly frustrating. I would much rather use my time building new features instead of fixing regressions introduced by poorly validated new models that have been shipped in iOS 27.
What frustrates me most is this change wasn't announced anywhere and there's no way to opt out. The revision number didn't change so there's no way to keep using the model that worked. If this had shipped as VNRecognizeTextRequestRevision4 apps could have stayed on VNRecognizeTextRequestRevision3 until they'd had a chance to test. Or permanently stayed on 'VNRecognizeTextRequestRevision3' as obviously the new version performs significantly worse.
Instead an app that worked fine on iOS 26 now gets wrong text back on iOS 27 with no error, no warning and nothing in the release notes. For a framework people rely on for real work that's a significant regression.
It seems that other developers have also come across this issue: https://developer.apple.com/forums/thread/845452
For technical reference, if you diff System/Library/PrivateFrameworks/TextRecognition.framework between iOS 26.5 (23F77) and iOS 27.0 (24A434) you uncover a number of changes.
New models on iOS 27 seem to use an '_e5' variant. The text detector in iOS 26 references training run 'yyzn76u6fs' with 88560 iterations, iOS 27 references training run 'hvcthxumvz' with only 10116 iterations. Perhaps an 8x reduction in iterations has something to do with the poor performance in iOS 27?
Further, the orientation model changes from iOS 26 'cr_orientation_model_v1' with 1858472 iterations vs. iOS 27 'cr_orientation_model_v1_e5' with 671065 iterations.
The Latin and Cyrillic Recogniser changed model entirely from 'cr_tr_model_latincyrillic_v3' on iOS 26 to 'cr_tr_model_latincyrillic_v3_e5' on iOS 27. It seems these 'e5' models are optimised for the neural engine.
- Is there any way to get the iOS 26 models/behaviour back or plans to back deploy the old model in iOS 27.1 or iOS 27.2?
- Can future model changes like this come with a new revision number?
- What testing process does the Vision Team use to validate models as clearly something was missed here?
Thanks!