Apple on Tuesday unveiled its next generation of iPhones — a line-up that will boast better cameras, faster processors, a new charging system and a price hike for the fanciest model.

The showcase at Apple's headquarters in Cupertino, California, comes as the company tries to reverse a mild slump that has seen its sales drop from last year in three consecutive quarters.

The malaise is a key reason Apple's stock price has dipped by nearly 10 per cent since mid-July, dropping the company's market value below the USD 3 trillion threshold it reached for the first time earlier this summer.

Investors apparently were not impressed with what Apple rolled out Tuesday. The company's shares were down by nearly 2 per cent during afternoon trading.

As has been case with Apple and other smartphone makers, the four types of iPhone 15 models aren't making any major leaps in technology.

But Apple added enough new bells and whistles to the top-of-the line model — the iPhone 15 Pro Max — to boost its price by USD 100, or 9 per cent, from last year's version to USD 1,200.

Apple is holding the line on prices for rest of the line-up, with the basic iPhone 15 selling for USD 800, the iPhone 15 Plus for USD 900 and the iPhone 15 Pro for USD 1,000.

All the new models will be available in stores September 22, with pre-orders beginning this Friday.

One of the biggest changes that Apple is announced is a new way to charge the iPhone 15 models and future generations. The company is switching over to the USB-C standard that is already widely used on many devices, including its Mac computers and many of its iPads.

Apple is being forced to phase out the Lightning port cables it rolled out in 2012 because of a mandate that European regulators plan to impose in 2024.

Although consumers often don't like change, the transition to USB-C ports may not be that inconvenient. That's because the standard is already widely used on a range of computers, smartphones and other devices people already own. The shift to USB-C may even be a popular move since that standard typically charges devices more quickly and also offers faster data transfer speeds.

The basic iPhone 15 models have been redesigned to include a shape-shifting cutout on the display screen that Apple calls its “Dynamic Island” for app notifications — a look that was introduced with last year's Pro and Pro Max devices. The basic models are also getting a faster chip used in last year's Pro and Pro Max models, while the next generation of the premium iPhone 15s will run on an even more advanced processor.

The iPhone 15 Pro and Pro Max also will be equipped with what Apple maintains is the equivalent of seven camera lens. They will include periscope-style telephoto lens that will improve the quality of photos taken from far distances.

The telephoto lens boasts a 5x optical zoom, which lags the 10x optical zoom on Samsung's premium Galaxy S22 Ultra, but represents an upgrade from the 3x optical zoom on the iPhone 14 Pro and Pro Max.

Apple is encasing the premium models in titanium that the company says is the same alloy used on some space ships.

Besides its new iPhones, Apple also announced its next generation of smartwatches — a product that made its debut nearly a decade ago. The Series 9 Apple Watch, available in stores September 22, will include a new gesture control that will enable users to control alarms and answer phone calls by double snapping their thumbs with a finger