This information is based on a leak courtesy of ShrimpApplePro, which was subsequently covered by Apple Insider in a dedicated article. According to the source, the iPhone 15 Pro Max could feature a panel with a peak brightness level of 2500 nits, which is being developed by Samsung.
The improvement could be limited to the high-end iPhone 15 Ultra, as Apple is reportedly working on ways of further differentiating iPhone models and widening the gap between the 6.1” and 6.7” high-end variants.
Nevertheless, this information should be taken with a grain of salt, given the mixed track record of the source. Additionally, there is still quite a lot of time until September 2023 when the iPhone 15 will likely debut.
For reference, the current max 2000 nits of the iPhone 14 Pro and iPhone 14 Pro Max remain mostly unchallenged, as even this year’s Samsung Galaxy S23 Ultra has a dimmer display.
It should be noted, however, that under normal circumstances the displays of the 14 Pro models seldom reach the peak level of brightness. It takes exposure to direct light and particularly sunny weather conditions in order for that to happen.
