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
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  • Formul - Monday, October 31, 2011 - link

    There is about a dozen fairly similar android phones every month. As iPhone gets refreshed just once every year (this time year and a half) and has bigger market than any single android phone out there it makes sense to make the review thorough. I guess Nexus Prime and even Razer will get similar lengthy reviewsa ... as did many other android phones before that (galaxy s2 for example had about the same as this one).

    You are the one biased here. Counting the number of android articles on any gadget blog will seriously outpace the iPhone by far. You should shut up and read what you want, no one is forcing you to read this blog or any particular article on it. I dont read android articles, i dont care about android all that much. Why do you have to troll here if it does not interest you after all?
    Reply
  • Anand Lal Shimpi - Monday, October 31, 2011 - link

    I believe we did just that for the Galaxy S 2 review:

    http://www.anandtech.com/show/4686/samsung-galaxy-...

    We don't have the RAZR, Galaxy Nexus or S2 Skyrocket, but we typically do a deep dive whenever there's a new platform transition or something truly unique to look at.

    Take care,
    Anand
    Reply
  • LordSojar - Tuesday, November 1, 2011 - link

    Hmm, touche Anand, I had forgotten about how detailed the S2 review was.

    The RAZR doesn't warrant a particularly detailed review I suppose, but I think the S2 Skyrocket might warrant a detailed antenna review etc considering the transition to LTE along with, what should be a major change to the antenna and should (I think) have QC's MDM9615 or MDM8215 chips in it... which is a big deal considering those could yield not only significant speed gains along with an antenna update, but some major throughput.

    Cheers
    Reply
  • doobydoo - Tuesday, November 1, 2011 - link

    'Samsung releases a new phone that has overall better features, faster CPU, faster NAND, a different and arguably better (or at least equal) screen'

    I hope you are comparing to the OLD Samsung, in this sentence, rather than comparing to the iPhone 4S.

    The CPU/GPU performance of the iPhone 4S is not comparable to the Galaxy S2, and I would argue the features are very much superior too.

    Which, incidentally, along with the dual-antenna design, Siri, brand new camera, makes the iPhone 4S much more of a step up than the Samsung Galaxy to Samsung Galaxy S2. (The Galaxy S was about the same performance as the iPhone 4. The Galaxy S2 is slower than the iPhone 4S, therefore iPhone 4S is a bigger upgrade).

    And of course, as Anand said, they thoroughly review most phones, and as the other poster says, the Android phones come out way more often so over the same length of time they get at least as much if not more coverage.
    Reply
  • Tetracycloide - Tuesday, November 1, 2011 - link

    The Galaxy S2 released in May. The 4S released in October. The next Galaxy phone, the generation the 4S is actually going to compete with, is the Galaxy Nexus. What I'm saying is your point would hold more water (or any at all) if Samsung didn't make 2 upgrades in the space of time it took Apple to do 1 so the differential between generations is hardly an apples to apples comparison (pun intended). Reply
  • thunng8 - Tuesday, November 1, 2011 - link

    But the Galaxy Nexus isn't any faster than the S2. The main benefit is the new operating system and higher resolution screen.

    The Nexus is actually a significant step backwards from the S2 in terms of camera (likely from the samples on the prototype) and GPU (definitely since it is using the SGX540) performance
    Reply
  • doobydoo - Wednesday, November 2, 2011 - link

    Release dates will not stop phone users comparing the iPhone 4S to the Androids released in March 2012, just like they compared all the Androids over the last 17 months to the iPhone 4.

    The iPhone 4S, right now, is competing with the Galaxy S2 directly.

    The Nexus Prime, as the other comment alluded to, is a significant downgrade from the Samsung Galaxy S2. Indeed, it uses the same GPU as used in the much older Samsung Galaxy S (albeit clocked higher).

    The Galaxy S to S2 took approximately a year inbetween generations (June 2010 to May 2011), which is very much in line with the typical Apple release cycle of annually (this year was the exception). Even this year, with the extended timeline between iPhone 4 and 4S, Samsung didn't make 2 upgrades during that time. Your point would hold more water (or any at all) if it had.
    Reply
  • Tetracycloide - Wednesday, November 2, 2011 - link

    It's obvious you're not making a real comparison between current products but instead of admitting that you pretend it's a non-issue and then strangely fought that issue anyway by suggesting I'm not actually right to call you out on these shenanigans. So thanks for being obtuse about this, it makes it much easier to dismiss your position as that of an irrational fan-boy (at least it does when combined with the condescension in some of the other threads you've commented on here). Reply
  • doobydoo - Friday, December 2, 2011 - link

    'It's obvious you're not making a real comparison between current products'

    Erm, huh?

    That's EXACTLY what I'm doing.

    What YOU'RE doing is asking is to compare a phone which isn't even out yet with a phone which is. You're trying to 'pretend it's a non-issue' that the phone you say the iPhone 4S should be compared with wasn't even out when this discussion started. THAT is the definition of fanboy-ism. It's like the constant like of Android fans 'x WILL be better when it eventually comes out' - and THAT is obtuse.

    So, the only comments which can be dismissed are YOUR fanboy comments about 'x phone released in x months will be better'. Turns out you were wrong anyway, but that's irrelevant - the bottom line is you don't want iPhone to be compared to CURRENT Android phones, but instead compared to FUTURE ones.

    Rational, much?

    As it happens, it's out now, and isn't even much of an improvement on the Samsung Galaxy S2
    Reply
  • Lucian Armasu - Wednesday, November 2, 2011 - link

    The cameras seem to be about the same, according to Anand. I've actually found the SGS II camera to be a bit better in photo comparisons. Siri? I still think it's more of a gimmick for now. Maybe in 5-10 years it will be actually useful. Once the novelty expires, people will barely even use it in a few months. The same happened with FaceTime which everyone went crazy about at launch, and then they stopped using it completely.

    The CPU of the SGS2 IS faster than iPhone 4S CPU. There's no way Apple managed to get a 50% performance improvement for the same Cortex A9 chip that Samsung is using.

    I think Anand can confirm this. He wasn't very clear in the review. He was only talking about the improvements it gets over the old Cortex A8.
    Reply

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