As many of you likely already realize, Apple announced two new camera-inclusive handhelds on Wednesday, the iPhone 5 smartphone (shown above, and also available in black) and the fifth-generation iPod touch. Both represent notable upgrades from their predecessors, both in terms of their image sensors and the image processing hardware connected to them. However, a cursory perusal of the iPhone 5's high-level specifications might incorrectly lead you to a different conclusion.
It's true that the iPhone 5's backside camera has conceptually similar specifications to the one in the iPhone 4S: an 8-megapixel resolution, and a five-element lens with f/2.4 aperture. However, it's been redesigned to be thinner before, in line with the overall iPhone 5 spec improvements; 18 percent thinner and 20 percent lighter than the iPhone 4S. This time around, the lens is also protected by a durable sapphire crystal cover.
If the iPhone 4 backside camera is conceptually similar to (albeit 25% more svelte than, and otherwise slightly altered from) the one in the iPhone 4S, how can the overall imaging subsystem feature set additions and enhancements be explained?
- Improved noise reduction
- 40 percent faster claimed capture speed
- Improved low-light performance through "dynamic low light mode" (likely a multi-shot noise reduction mode)
- built-in real-time panorama mode multi-image 'stitching' (also supported on the fifth-generation iPod touch and iPhone 4S, albeit at slower performance and potentially lower quality)
That's where Apple's new A6 ARM-based SoC, which according to the company also embeds an improved image signal processor, factors into the equation. Apple claims that the A6 delivers up to 2x the CPU and 2X the GPU performance of the A5 SoC in the iPhone 4S, but hasn't provided any CPU or GPU core specifics. As review, here are the high-level specifications on the A5 and A5X, the latter found in the "Retina" display-inclusive "new iPad" (i.e. iPad 3), therefore explaining the GPU upgrade.
A5
- 45 nm fabrication process (later lithography-shrunk to 32 nm)
- Dual-core 1 Ghz (iPad 2) or 800 MHz (iPhone 4S) ARM Cortex-A9 CPU
- -Dual-core Imagination Technologies PowerVR SGX543MP2 GPU
A5X
- 45 nm fabrication process
- Dual-core 1 Ghz ARM Cortex-A9 CPU
- Quad-core PowerVR SGX543MP4 GPU
When previously announcing the A5X, Apple claimed that its GPU was twice as powerful as the one in the A5, so it's seemingly unchanged on the A6 successor. But what about the CPU? Apple has at least three different means of accomplishing the claimed 2x improvement versus the A5 and A5X's dual-core ARM Cortex-A9:
- Per-core clock speed improvements (note that the "base case" is the 800 Mhz CPU speed bin in the iPhone 4S, not the 1 Ghz variant in the iPad)
- Additional CPU cores (it's not absolutely necessary for Apple to further double the A5 core count to four…Marvell makes at least one tri-core ARM SoC, for example)
- A newer per-core CPU generation…from the Cortex-A9 to the Cortex-A15, or maybe even a big.LITTLE arrangement
AnandTech believes that Apple's new A6 has the Cortex-A15 inside, and the stance is reasonable, particularly considering that Apple's foundry, Samsung, is also sampling a Cortex-A15-based SoC, the Exynos 5250. Others, however, aren't so sure. Regardless of how (and if, for that matter) Apple accomplished its CPU performance improvements, they're also available for use by the front-side image sensor, which has been even more dramatically improved in the iPhone 4S-to-5 transition. The iPhone 4S front-side camera, unchanged from that in the iPhone 4 (and for that matter the second- and third-generation iPads) is VGA (0.3 Mpixel) in resolution and captures 480p video. Its successor in the iPhone 4 captures 1.2 Mpixel still images and 720p video.
The fifth-generation iPod touch has also received notable improvements from its predecessor. The CPU is now the A5, versus the A4. The rear-view camera increases in resolution from 0.7 Mpixels to 5 Mpixels, with a corresponding video frame size increase from 720p to 1080p (both at 30 fps). And the front-side camera similarly increases from VGA to 1.2 Mpixel still resolution, and from VGA to 720p video capabilities.
Followup: credible evidence suggests that Apple has secured an ARM instruction set (i.e. architecture) license and has used it to design a custom ARM CPU core for the A6, akin to Qualcomm's Snapdragon and Krait SoCs, and to Marvell's Armada product line.
