Improved ISP in A5

So we’ve been over the optical system and the sensor, but there’s another factor as well - image signal processing (ISP). It surprised me to see Apple bring this up on stage, but it’s a hugely important point to make, that the quality of images captured on a given platform depends on everything in the image processing chain. The A5 SoC includes an improved ISP over what was in the A4, and is referred to as the H4. You can watch the OS power gate the ISP and activate it when you launch the camera on console as well:

Oct 18 16:35:02 unknown kernel[0] : AppleH4CamIn::ISP_LoadFirmware_gated: fw len=1171480 Oct 18 16:35:02 unknown kernel[0] : AppleH4CamIn::ISP_LoadFirmware_gated - firmware checksum: 0x0545E78A Oct 18 16:35:02 unknown kernel[0] : AppleH4CamIn::power_on_hardware

The changes include faster processing to accommodate an 8 MP sensor, and vastly improved white balance (which we will show later), and finally some face detection algorithms that work in conjunction with autofocus and autoexposure. I’ve also noticed that the A5’s ISP seems to have improved AF speed (it’s hard to measure, but it just seems much faster) and more importantly the framerate of the capture preview is much higher. I’ve included a small video showing just how much smoother the 4S looks than the 4, even on my 1080p60 camera (which YouTube then reduces to 30fps) the difference is noticeable.

When the ISP detects a face, it’ll paint a green rectangle over the region and run the AF/AE routine just like it would if you tapped to focus. Like all face detection algorithms, it’s decent but not perfect, and I saw the face detection rectangle come up while shooting pictures of pumpkins at a pumpkin patch (which was fairly repeatable on one pumpkin), and a few other random occasions. Apple claims their ISP will run face detection on up to 10 faces and balance AF/AE accordingly for the best exposure.

I mentioned that the camera application preview framerate is improved - which it is - but the camera application is also speedier. Word on the street is that camera application launch time was a significant focus for the 4S, and I set out to measure the difference over the predecessors cameras. Camera launch time is one thing that was singled out during the presentation, but another that can be measured is HDR processing time. I quit all tasks and launched the camera application fresh five times (from tapping camera to seeing the iris fully open), then averaged.

Camera Performance Comparison
Property iPhone 3GS iPhone 4 iPhone 4S
Camera Launch Time (seconds) 2.8 2.3 1.4
HDR Capture Time (seconds) - 4.9 3.2
Working Distance (cm) ~7.0 7.0 6.5

The result on the 4S is a bit behind Apple’s quoted 1.1 seconds, though it’s possible they were measuring after an initial launch, whereas I’m starting with the camera completely closed each time. Still, 0.3 seconds isn’t that far away from their own measurements. The 4S is almost an entire second faster at launching the camera app than the 4, and 1.5x faster at merging three images to HDR than the 4. I also decided to get a rough measure of working distance on the three cameras, or the closest an object can be to the camera and still be focused on.

Camera Improvements Still Image Capture Quality
POST A COMMENT

199 Comments

View All Comments

  • doobydoo - Friday, December 2, 2011 - link

    Hardware wise, the difference between the iPhone 4S CPU/GPU combination and Android competitors, is huge.

    If you want the best performance, I don't see any other way to turn.

    As for the software, I like most users would happily use Android or iOS - they've largely converged anyway.
    Reply
  • name99 - Friday, November 4, 2011 - link

    "If you had a 4 already your just a "moop" if you upgraded to one of these!"

    OK, so most US customers on on a 2yr plan. Upgrading for them is impractical, if for no other reason then for carrier reasons. And then you are COMPLAINING that Apple produced an upgrade that (in your eyes) gives them no reason to upgrade???

    What exactly is your problem? You're like someone who goes to a restaurant and complains "the food sucks --- and the portions are too small".
    Reply
  • dennykins - Tuesday, November 1, 2011 - link

    Hey! I have that "Introduction to Modern Optics" book too! Pretty old, but still relevant Reply
  • name99 - Tuesday, November 1, 2011 - link

    "It is admittedly curious that Apple hasn’t decided to make some other larger change to distinguish the 4S from the other two"

    There was, of course, also precious little visual change between iPhone, iPhone3G and iPhone 3GS. Likewise for plenty of other upgrades across the Apple line in the last ten years. I don't know why Anand thinks it's strange. For YEARS Apple has made the point that you buy an iMac --- and you get the what Apple thinks an iMac should be today. You don't buy an iMac XV371. You don't buy an iMac 7. You don't buy an iMac 20011. You buy an iMac --- which may or may not look like its predecessor, which may or may not have last been updated three, six or
    nine months ago.

    It's obvious that Apple wants to bring that same mindset to phones (and iPads). Screwing with people's expectations of an update in July was simply the first step in breaking the mindset of a particular schedule for upgrades. Of course there are issues that make it more difficult to do this cleanly, for example carrier involvement and the ridiculous subsidized pricing model --- which means that Apple has reason, at least for now, to keep older models around. But there are obvious advantages to Apple in switching to this model, including
    - not being forced to release SW too soon. I think we'd all agree iOS5 was released under pressure, and that iOS 5.1 will be the release 5.0 should have been.
    - Apple's been able to ignore pressure from a stream of constant Android updates for the past two years, but at some point annual upgrades may just be too slow. At that point it would be nice to have the option of minor upgrades (cf the recent PowerBook Pro upgrades), say boosting the CPU from 800 MHz to 1GHz, without it being a big deal --- something to shut up the crowd that looks at specs, while being ignored by the mass audience that does not care about specs and doesn't want Apple talking about them.

    Not that this will stop haters from claiming that "people buy iPhones for fashion"....
    Reply
  • KPOM - Tuesday, November 1, 2011 - link

    Good observation about the upgrades. Yes, it's entirely possible we'll see minor spec bumps as the iPhone has become a staple of Apple's product line. We don't notice all the the upgrades in the Android world (how many people know or even care about the differences between the Galaxy S, Galaxy S II, and Galaxy S II Skyrocket ?), partly because they happen all the time.

    Also, Apple has never been a company to change the design simply for the sake of change. They tweak a design until they "get it right," but then stick with it a while. This year's MacBook Air, for instance, is a big update from last year's (Core i5/i7, backlit keyboard, 4GB RAM standard on most models), but they didn't change the external design. It's still selling extremely well and received good reviews. I think it's the same with the iPhone. The 4S has some significant improvements, from the faster processor, better camera, and better antenna.
    Reply
  • name99 - Tuesday, November 1, 2011 - link

    I'm glad you guys adopted my suggestion to report how snappy a phone feels, based not only on CPU benchmarks but also on the speed of flash, and things like the launch time of apps.

    In the spirit of constant complaint that is the web, can I now ask that you continue to do this for all future phones, not just iOS devices.
    Yes, you have fanboi readers who care only about how wonderful their platform is; but you do also have a number of honest readers who are genuinely interested in things like how the speed of flash (including the speed of SD flash) varies across devices, and how launch times (for comparable apps) vary --- which, of course, depends on both HW and also SW/OS decisions.
    Reply
  • Drasca - Tuesday, November 1, 2011 - link

    There's a small typo that I'm surprised no one else has caught. Perhaps I am the only one that cares enough about this particular subject enough to. On the last page, 4th to last paragraph, we see:

    "we’ll hopefully see the technology mature into something more like what years of science fiction moves have promised us."

    I believe you mean movies here.

    I caught it in particular because I've been discussing amongst my friends how modern technology is the future promise of older science fiction. Oh gosh gee wiz, we have instant mobile communication across the globe, including video! We talk into our portable devices and they think for us. These devices are an extension of ourselves. In a way, we've become like the borg in that we're connected to community at large. Facebook is a form of hive mind group consciousness. Heck, we can track each other near-instantaneously and some folk are vividly aware of each other's locations.

    These are interesting times, and what has only previously been explored as supposition has become reality.

    I still want my flying cars and teleporters. Also, Holodecks and the AI behind it. Plus, the bridge of the starship enterprise D with its big comfy captain's chair and massive screen.
    Reply
  • anishannayya - Wednesday, November 2, 2011 - link

    If you want an iPhone, you really don't have a choice. Either you get the 4S or go find an Android phone. Reply
  • shashank7040 - Wednesday, November 2, 2011 - link

    Asus Eee Pad being the first tablet With Slide out QWERTY........http://goo.gl/B4rJU Reply
  • thevibenow - Wednesday, November 2, 2011 - link

    Check out our review of the Iphone 4s

    http://www.youtube.com/watch?v=35v1kkaPM9s
    Reply

Log in

Don't have an account? Sign up now