Behind SGS2's Camera - Still Quality

Now the next subject is still image capture on SGS2. Before I go any further, I think now is as good at time as any to talk about what sensors are in the device. Getting to the bottom of this took some poking around, and where I started was the camera firmware. Usually getting what sensors are used in a given device is pretty straightforward - look for driver messages in dmesg when the kernel boots, and then see which ones correspond to cameras. However, on SGS2 the thing is hidden behind a custom ISP that talks over I2C to Exynos, which didn’t lead me much further than just finding out what particular ISP is onboard.

I opened the camera firmware (from /system/etc/firmware ) in a hex editor and fired away. There are number of interesting things which pop up. First up is this:

Softune REALOS/FR is Realtime OS for FR Family, based on micro-ITRON
COPYRIGHT(C) FUJITSU LIMITED 1994-1999

So we know that the ISP is Fujitsu. Then there’s a line like this:

Copyright (c) 2005-2008 by FotoNation. All rights reserved.
Face Detection Library v.1.2.58.7

and finally:

OBED04 Fujitsu M5MOLS

all strewn among a bunch of padded bits and compiled code incorporated into the SGS2’s “camera” firmware. So what’s the real story? Well, SGS2 uses a Fujitsu Milbeaut M–5MO ISP paired with one of two cameras. To find out which camera SGS2 uses, I took a look in Francois’ SGS2 kernel repo under the actual M5MO C driver file. Inside, there’s a line like this inside a function named “m5mo_camera_type_show”:

    if (state->exif.unique_id[1] == 'B') {
    strcpy(type, "SONY_IMX105PQ_M5MOLS");
} else if (state->exif.unique_id[1] == 'C') {
    strcpy(type, "SLSI_S5K3H2YX_M5MOLS");
} else {
    cam_warn("cannot find the matched camera type\n");
    strcpy(type, "SONY_IMX105PQ_M5MOLS");
}

So we now know that inside SGS2 is either a Sony IMX105, or Samsung S5K3H2YX sensor. This is basically the same exact camera lottery situation that the MyTouch 4G Slide is in, as it in fact has the same two exact sensors listed, though F/2.2 optics. Both are basically the same on paper and should offer similar performance - 1/3.2“ size, 1.4µm backside illuminated pixels, and 8.13 MP (3264 x 2448). The front-facing camera uses a Samsung S5K5BAF 2 MP sensor sized 1/5” and with 1.75µm square pixels.

Interestingly enough, I believe I was able to find the actual module which Samsung uses inside the SGS2 on a Samsung fiber optics website, using the Sony IMX105 module. Take note of the appearance of this module, as it’s virtually identical to what I saw inside the device as I’ll show in a moment.

Having two sensor suppliers isn’t anything new, Apple has done it (and will continue to do so), HTC is doing it, and now Samsung is doing it too. With the same on-paper sensor performance and the same autofocus + optical system module, things should all work out and photos should look the same no matter what sensor is inside.

Other specs about the camera module are that EXIF reports an F/2.7 aperture and 4.0 mm focal length. This is a bit odd to me since F/2.8 is on the typical full-stop scale (2*sqrt(2)), and then F/2.4 is a next half-stop, and I’m only aware of IMX105 coming in F/2.4 and 2.8 modules. Just goes to show that sometimes EXIF data is weird. The module is most definitely the F/2.8, f=4.15 mm variant with a 28.1 degree horizontal field of view and 4 plastic aspheric lenses.

As an aside, if this whole system sounds familiar, it’s because the Sony IMX105 module with F/2.4 optics is the oft-rumored camera going into the next iPhone.

So that brings me to the infamous magenta circle issue which numerous people have reported seeing on their SGS2s. The last time we saw this was with the iPhone 4, where a green circle is readily apparent under certain light conditions or when photographing a homogenous color or texture. Some users have reported seeing a similar magenta circle on the SGS2 camera when photographing under similar conditions, so I set out to replicate it.

The closest I can get to the magenta circle

For better or worse, I can’t see the magenta circle on the SGS2 we were given, though I don’t doubt that some devices do show it. It doesn’t take much to extrapolate and come to the conclusion that is in part due to what’s becoming a CMOS lottery - now not only is there a display lottery (like what notebook buyers have been dealing with for a long time), but a CMOS lottery for sensors.

The magenta circle I see on this SGS2 is faint and nowhere near as pronounced as the green iPhone 4 circle, nor the SGS2-captured images I’ve seen online. Further, I haven’t been able to devise a method to tell which of the two possible sensors are inside this particular SGS2. I’ve taken some photos of completely white objects at a variety of focus positions and under different lighting conditions for your own perusal.

We’ve done the usual thing too and taken photos with the SGS2 inside our lightbox test scene, with the lights on and lights off. With the lights on, the SGS2 has a hard time nailing white balance with the test illuminated in auto mode, and in manual mode (set appropriately) it still has the wrong color temperature. This is just a bit unfortunate since otherwise sharpness is excellent, there’s little noise, and little to no chromatic fringing at the edges. I’m very impressed with camera performance here and would encourage viewing those images 1:1.

On the front facing camera, we get performance that looks actually surprisingly good. So good that it could actually pass for rear facing camera quality (resolution notwithstanding) of some previous generation devices.

With the lights out, the SGS2’s single LED flash illuminates the test scene nicely and gives good color temperature. SGS2 also does the right thing and fires up the LED for autofocus in the dark.

Next, we took photos with the SGS2 at the usual test locations, and it’s here that SGS2’s camera really shines. As a reminder, test locations 3, 4, 6, and 7 are the only ones remaining that I can visit, so skip 1, 2, and 5. SGS2 just really has great well-corrected sharpness and performance even out at the edges where aberrations take off, good colors without insane saturation, and great dynamic range.

Finally, I captured a large number of miscellaneous photos with the SGS2’s rear facing camera as well. I think in these real-world scenarios we get to see a better example of the SGS2’s camera performance, which is extremely good among the smartphones we’ve seen so far. Samsung also doesn’t make the mistake of putting the last vertex of the camera system behind a piece of plastic integrated into the battery cover. Instead, the module juts out through the battery cover in a way that doesn’t allow dirt and dust to collect.

Camera UI and Video Quality Inside the SGS2
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  • dagamer34 - Sunday, September 11, 2011 - link

    On pg 15, Galaxy S uses a SGX 540 GPU, not 530. Other than that, great review! Reply
  • Synaesthesia - Sunday, September 11, 2011 - link

    Staggering review, you really are the most comprehensive and scientific reviewer around, bravo!

    Samsung have really impressed with this phone, in terms of how much effort they have invested in the hardware and software. One thing still stands out for me, the battery life. While good, it still doesn't hold a candle to the iPhone 4, as shown on the charts.
    Reply
  • LostViking - Saturday, September 17, 2011 - link

    What do you mean?
    Its about 30% worse when web browsing (mostly because of the much larger screen I reckon), but better in the other tests.

    If you are one of those old timers who actually use the phone for talking the SGSII is about 30 better ;)
    When I am low on battery, and don't have access to a charger, that's usually what I would prioritize.
    Reply
  • xdrol - Sunday, September 11, 2011 - link

    For me the mentioned Cat 5 limit looks reasonable - you don't get user-level 2.0 Mbps because of the overhead of the PDCP/RLC/MACd protocols (about 15% -> 2.0 Mbps is 1.7 Mbps for IP). Reply
  • wilky76 - Sunday, September 11, 2011 - link

    Alot of people that have the Samsung Galaxy S2 are suffering from framerate problems when using either 720p or 1080p in low light including myself.

    What basically happens is when the camera tries to focus in lowlight the framerates drop to around 13fps, then jump back upto around 30fps again, basically making any HD video recording useless in low light because of the stuttering, the only fix that is known is to drop the exposure to -2 as this stop the stuttering, or use 480p when indoors or poor light.

    Some folks have returned their SGS2 because of this problem, only to receive another with the same problem.

    There has been a couple of camera firmware updates on Samung own app site, which to this date still hasn't sorted the problem out & in some cases people that weren't suffering from this problem, now have it after updating the camera firmware.

    Can any of you guys at Anandtech test your SGS2 in low light with either 720p or 1080p to see if the mobile you received for reviewing also suffer from this problem.

    But what is strange is that not everbody has the framerate problem, so it could be due to which sensor you get with your SGS2, and could proberly be sorted with a firmware update eventually.

    Anyways people with this problem and there is a few can be found in this post over at XDA

    http://forum.xda-developers.com/showthread.php?t=1...
    Reply
  • DrSlump - Monday, September 12, 2011 - link

    Hi, i have exactly the same problem with my samsung galaxy s2.
    I got casual stuttering (a frame loss) during normal light conditions and severe stuttering under low light conditions.
    As soon as the firmware raises the sensor gain to match the detected light, the framerate goes down to 25fps and when autofocus occours the framerate goes down to 13fps, and then returns back to 25fps when the autofocus is finished.
    I olso noticed that when i try to frame a tv or a monitor, severe banding occours. Even taking a video when the light source is a tv or a monitor, banding occours. Seems like the isp isn't able to compensate the frequency of the light source.
    In a lot of situations it's impossible to take a video due to the severe stuttering :(
    Any one of you has these problems? How to solve it?

    I would like to ask to the autor:
    did you notice some problem with the display? There is a thread in the xda-developers forum that speaks about the yellow tinting or faded out left side of the screen. Please can you report about this problem?
    Reply
  • B3an - Sunday, September 11, 2011 - link

    Why dont you just admit it's the best phone around hands down? :) Not just the best Android phone. It's clearly miles superior to the outdated iPhone 4.

    Shame you yanks have had to wait forever to get it, only to get 3 different versions that dont even look as good and have ridiculous names. I've been using a GSII since April and it's just unmatched.
    Reply
  • ph00ny - Sunday, September 11, 2011 - link

    This yank got it on the UK launch day and i've been enjoying it since Reply
  • steven75 - Sunday, September 11, 2011 - link

    It's not better in battery life, audio quality, display resolution and sharpness, or the many ways that iOS is better (AirPlay, app selection AND quality), immediate OS updates, etc).

    Gread Android phone though for those interested in 4.3" displays, which definitely isn't everyone. Personally, I'd wait for the Prime.
    Reply
  • steven75 - Sunday, September 11, 2011 - link

    Oh and outdoor display brightness, which even at 100% isn't a match for iPhone, but then it's even capped at 75% for temp reasons. Reply

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