One of the big improvements that comes with the iPhone 5S is a new camera system, with a faster aperture for more light throughput, bigger 8 MP sensor with correspondingly bigger pixels, dual LED color temperature matching flash, and improved ISP. I thought it worth going over some of the changes before we look at it in the review since there’s already honestly quite a lot that I’ve gathered about the 5S system just from examining EXIF on the images from Apple’s uploaded sample images gallery, what I saw in the demo room on a 5S, and what has been said publicly.

Camera has become one of the major axes of differentiation in the smartphone space. It doesn’t take much inspection to see that it has become an emphasis everywhere. Nokia has had halo devices for a long time now which establish its position with dominant smartphone camera leadership, HTC recently pushed its imaging emphasis very far with the One’s camera system and arguably the system before it for the One X and S, and even the recent Moto X made an attempt to do something fundamentally different with a color filter array including a clear pixel. Obviously the iPhone sits somewhere in that fray if nothing else since Apple really started demonstrating something above normal camera competency around the 3GS and 4 by shipping a system of its own design and specification. Since then, Apple has continued to push parts of its imaging chain further with a custom Sony CMOS starting with the 5 and custom ISP with the 4S. Obviously the statistic that Apple will cite is that the iPhone cameras take the top 3 spots on Flickr for camera popularity, making them arguably some of the most important cameras out there. Given my optical engineering background, watching smartphone cameras evolve and move in different directions is of course particularly interesting since it’s a place in the camera world with unusual constraints. As a photographer I’m also interested in finding ultimately what device has the best usability to camera tradeoff ratio, and Apple has historically made sound choices with its system.

iPhone 4, 4S, 5, 5S Cameras
Property iPhone 4 iPhone 4S iPhone 5 iPhone 5S
CMOS Sensor OV5650 IMX145 IMX145-Derivative ?
Sensor Format 1/3.2"
(4.54x3.42 mm)
1/3.2"
(4.54x3.42 mm)
1/3.2" ~1/3.0"
(4.89x3.67 mm)
Optical Elements 4 Plastic 5 Plastic 5 Plastic 5 Plastic
Pixel Size 1.75 µm 1.4 µm 1.4 µm 1.5 µm
Focal Length 3.85 mm 4.28 mm 4.10 mm 4.12 mm
Aperture F/2.8 F/2.4 F/2.4 F/2.2
Image Capture Size 2592 x 1936
(5 MP)
3264 x 2448
(8 MP)
3264 x 2448
(8 MP)
3264 x 2448
(8 MP)
Average File Size ~2.03 MB (AVG) ~2.77 MB (AVG) ~2.3 MB (AVG) 2.5 MB (AVG)

With the iPhone 5S camera, Apple makes a number of interesting changes that I already touched on. Rather than march down the pixel size roadmap to 1.1µm (and beyond that the upcoming 0.9µm step) to either increase pixel count with an equivalent sized sensor, or shrink the sensor and optical stack and maintain the same number of pixels, Apple has chosen a strategy like HTC’s and gone the other way. Apple has increased pixel size to 1.5µm (from 1.4µm), while keeping pixel count the same, thus creating a larger sensor. I remember telling Anand and a number of other people that if Apple even just stayed at 1.4µm for the 5S, it would mean validation of everything I ever said about the 1.1µm size and beyond in my prior smartphone imaging and optics presentation.

Obviously seeing Apple put up a "bigger pixels = better picture" slide during the keynote and move the opposite direction by bucking the trend just like HTC did makes me a lot more comfortable about the future of Apple’s smartphone imaging roadmap. Increasing pixel size is arguably the better but simultaneously harder direction for the industry to increase image quality, low light sensitivity, and SNR. Keep in mind that I’m talking about pixel pitch here, so Apple’s increase from 1.4µm to 1.5µm pixels really means a 14.8 percent increase in pixel area and thus integration area. If you do the math out, Apple moves from the relatively standard 1/3.2“ CMOS sensor size to around 1/3” in size, similar to the HTC One. Increasing sensor size and pixel size really will make a measurable difference in low light sensitivity, noise, and dynamic range. I don’t know any specifics but given Apple’s ability to get Sony to make a one-off custom CMOS for the iPhone 5, I wouldn’t be surprised to see Sony supply a sensor of Apple’s specification this time for the 5S, one of the nice things about having their kind of volume.

At the same time, the optical design has improved to increase the amount of light passed through the system. Apple’s 4S and 5 systems were F/2.4, the iPhone 5S system moves down a quarter stop to F/2.2. I was hoping for F/2.0 like we see a number of other OEMs shipping (HTC, Nokia) but F/2.2 might be a logical tradeoff to keep aberrations down and not run into some of the stray light issues that I’ve seen crop up in those other systems. The 5 had stray light issues that famously resulted in some purple fringing already at F/2.4, which people falsely attributed to the sapphire cover glass (which is actually colorless). It remains to be seen whether the lower F/# on the 5S increases them, though I wager the attention given to this issue probably resulted in some correspondingly better anti reflection coatings and stray light management.

Focal length changes slightly, from 4.10 mm in the 5 to 4.12 mm in the 5S. The difference in sensor size and thus crop factor gives a 35mm equivalent focal length of around 31mm in the 5 and 29.7mm in the 5S. Shorter focal length has generally been a tradeoff for a while to decrease the z-height of the module further, and you see a lot of smartphone vendors hovering around 28mm or slightly lower, which is relatively wide. Marketing will then turn around and market the wider angle like it’s some positive thing, which is hilarious. Apple has thus far been steadfast at staying around 30mm, but there’s no denying that the 5S will indeed be a bit wider angle than the 5 in practice. Ideally I’d love to have a smartphone module with around a 35mm focal length in 35mm equivalent numbers.

The most visible and talked about change for the 5S imaging system thus far is the dual LED “true tone” flash, which really is a system with two LEDs of different color temperature. Spectral output of LEDs tend to be a bunch of narrow bandwidth spikes, which results in weird color rendering (analogous to the sometimes poor color rendering index of LED lightbulbs or CCFLs). In addition, white LED flashes just end up having a blue tint compared to Xenon. The solution is to add another color temperature alongside, then mix the two LEDs to get the desired color temperature that matches the scene. I actually saw NVIDIA doing this dual color temperature LED flash mixing on their Tegra 4 reference tablet back before MWC, and this is something other OEMs have been talking about, Apple just has the first device to market with it.

I played around with the flash in the demo area, and the 5S system pre-flashes, computes the correct flash amplitude to match scene color temperature, and then fires a flash during capture with the right color temperature.

The result is a photo that does look better in terms of color rendering and temperature. Personally I still have a deep seated dislike of on-camera or direct flash, and only use it when natural light is absolutely insufficient to get a photo. I don’t think this will really change my feelings about on-camera flash, but if you do have to use flash to light a dark scene, this makes it a lot less terrible.

Finally there are improvements to ISP and video encode. The 5S includes a further improved ISP, though I have no way of knowing what’s new inside beyond what Apple stated during the keynote, and in general SoC ISP remains a closely guarded secret for all of the silicon players. Apple purports their new ISP has improved AWB, AE, new local tone mapping, new autofocus matrix metering with 15 focus zones, and automatic selection of the sharpest image in the capture buffer when you finally do press capture. Of course there’s also a new burst capture mode which activates when holding down the capture button and captures at 10 FPS. I held this down in the demo area and took around 500 images without the speed slowing down. Apple is probably buffering these in DRAM and writing them to NAND at the same time.

On the video side the 5S now includes a 120FPS capture mode. The camera UI has a “slow-mo” option beyond the video mode, which captures 720p120 video. The framerate in this mode in the camera preview is visibly faster, capture works like normal, but inside the playback UI are two scrubbers which let you play back that 120FPS video at 30 FPS, making it look 4x slower. I’m unclear whether the 5S makes the raw 720p120 video available, but I really hope that’s the case. I do wish that there was 1080p60 capture, but that might be exposed through the video capture APIs somewhere, again it’s still unclear.

What’s missing from the 5S is OIS. I didn’t ever think it was in the cards for the 5S, so its absence isn’t a surprise, but it’s a substantial improvement for video and longer exposures. The reality is that an increasing number of players are including it – Nokia, HTC, and LG, and that list will only continue getting larger. Its absence isn’t the end of the world, but the stronger OIS implementations make a substantial difference for both videos and still images. Apple’s going the electronic and computational route with further improvements to its EIS auto image stabilization, which combines the sharp parts of multiple images together to get a single sharp picture. Almost every smartphone camera system now has a back buffer of images coming from the sensor, Apple purports that it is able to do some computational analysis, grab sections of the last few images and combine them to produce a sharp result. This will help in good lighting where the system can grab a lot of images quickly with good exposure, but obviously doesn’t fundamentally solve the low light problem where the exposures themselves are still longer. Grabbing photographs without blur remains a challenging problem for everyone, obviously OIS doesn’t help with scenes where the subject is moving either.

I’ll add that I’m still unclear whether the 2x2 pixel binning remains in place with the 5S camera. I would be surprised if it wasn’t in place however, especially given the 720p120 recording mode which would require it to get the higher sensitivity required for higher framerate. Higher framerate video capture means less integration time per frame to gather light.

Selected EXIF from Apple's iPhone 5S Sample Photos:

Make                                         : Apple
Camera Model Name               : iPhone 5s
Exposure Time                   : 1/1866
F Number                        : 2.2
Exposure Program                : Program AE
ISO                             : 32
Metering Mode                   : Spot
Flash                           : Off, Did not fire
Focal Length                    : 4.1 mm
Focal Length In 35mm Format     : 30 mm
GPS Altitude                    : 15.8 m Above Sea Level
GPS Latitude                    : 38 deg 1' 22.22" N
GPS Longitude                   : 122 deg 31' 22.23" W
GPS Position                    : 38 deg 1' 22.22" N, 122 deg 31' 22.23" W
Image Size                      : 3264x2448

A few iPhones ago, Apple started posting sample images from their new iPhone camera in full resolution taken straight from the device on their own site right after the announcement. That has turned into common practice now, and the 5S is no exception. I’ve gone over the images each time and looked at EXIF for whatever info is available (and the GPS tags that generally were left on), and did the same for the 5S. Interestingly enough Apple only left location tagging on for one of the 6 images (the skateboard pic) this time around.

5S: 1/2740, ISO 32

The photo samples look very good. None of the photos go over ISO 100, in fact most of them are at a very low ISO 32 which keeps noise down. Exposure times are also very fast. Only image 3 is somewhat low light looking. I was hoping Apple would include a few samples showing low light performance indoors with and without flash, but I guess I’m not surprised Apple would pick scenarios that show off the best quality rather than situations that might strain it. For that we’ll have to wait.

  • Image number one which is a macro shot of a flower has a nice looking blurry background effect without distracting or artificial looking bokeh. For a smartphone camera this looks very good.

  • Image number two is a top down shot of some chilis on a wood table, relatively planar. What’s awesome here is it lets me see immediately that there’s good sharpness across the entire field of view – the edges don’t get soft like a number of other smartphones do. Maintaining good MTF across the entire field of view is difficult, especially at extreme field angles like the corners. While there’s definitely some falloff, it’s very controlled on this 5S sample photo. In addition there’s no weird distortion, the horizontal grains in the wood remain horizontal for example.

  • Image number three is of a jellyfish, and is the only somewhat lower light photo, though I’m not convinced this is what I’d consider low light. It looks good but moreover illustrates that the auto exposure algorithm in the 5S isn’t just blindly taking exposure over the whole scene (the black aquarium) – spot metering mode is noted in the EXIF indicating the user tapped the jellyfish.

  • Image four is an impressive sunset, although here the bokeh is a bit more distracting and weird looking in the background. Sharpness is retained however in the grass close to the sunset bloom, without washing out. I also don’t see any fringing.

  • Image five is of some kids in a pool, skin tones look great here against the water, sharpness is also great.

  • Image six has action nicely frozen and was probably captured using burst mode, if there’s any opportunistic image recombination here for the scene, I can’t detect it in the output result.

The camera UI in iOS 7 also gets a substantial overhaul. Gone is the still image capture preview which is fit to the long axis of the iPhone 5/5C/5S display, which crops off the top and bottom of the image. Thankfully, Apple has come to its senses and changed the UI so the full field of view of the image is visible, and what you see is now what you get. If only Google would now follow suit and do the same to the AOSP/stock Android UI.

The camera UI has completely different iconography and styling from the old one. Gone is the video toggle, and in its place is a mode ring which switches between slow-mo, videos, photo, square, and panorama. This eliminates some of the feature cruft that was piling up in the “options” button from the old UI. There’s also the filters option which shows a live preview grid of some filters on the image – think photo booth for iOS. My only complaint is that whereas the previous iOS camera UI had more visual cues that made it easy to confirm the camera detected proper portrait or landscape orientation, the iOS 7 camera really doesn’t. Only the thumbnail and flash/HDR/front camera icons rotate. Further, the text ring switcher doesn’t rotate, which adds some mental processing when you’re shooting in landscape (which you should, especially for video).

I explored the iOS 7 camera UI and slow motion features on the iPhone 5S a lot in our hands on video which I’d encourage you to check out.

Overall the improvements to the 5S camera system are very positive and I’m very happy to see Apple going the direction of bigger pixels rather than marching down the pitch size roadmap and trading off sensitivity. Larger pixels and bucking that trend is absolutely positively the right direction to go. If Apple went the other way I’d start getting concerned about the camera team over there. Obviously the choices made in the 5S do a lot to put me at ease and reassure that there’s still some sanity in the smartphone imaging space. Likewise the dual color temperature LED flash system is another low light improvement, even if I still dislike on-camera flash in general and will probably never use it – every iPhone I’ve ever owned has had flash set to off rather than auto. Faster F/# is a big improvement along that same axis as well, letting in more light and possibly giving more shallow depth of field at some focus positions. High framerate video coming to the 5S was a no brainer given the new APIs and features added to iOS 7, I just assumed it’d be 1080p60 rather than 720p120, although there’s still a chance that 1080p60 is an option through the capture API rather than the camera UI. Finally I’m very happy that Apple has sorted out the aspect ratio cropping issues in the camera UI that really frustrated me with the iPhone 5’s display ratio change. The end takeaway is better low light performance compared to the 5 at the same resolution, substantially better LED flashes when native light doesn't get you far enough, and of course those extra added features like burst mode and 120FPS video record.

Most of my time getting hands on with the iPhone 5S in the town hall demo room was spent playing with the camera UI, but there’s only so much you can really tell given a few minutes. Either way the iPhone 5S looks to be another big improvement to Apple’s very popular camera system.

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  • akdj - Friday, September 13, 2013 - link

    You don't have to shoot in burst mode. You still have a single shot option. It's definitely not 'stupid' (the burst mode---it's actually extremely intelligent). In fact...it's extremely ignorant for you to consider this type of engineering 'stupid' in any sort of discussion. It's by far and away one of the hardest and challenging types of engineering considering the spatial limitations inside of a 'phone'. Reply
  • Impulses - Friday, September 13, 2013 - link

    Shooting a quick burst and picking the best one is pretty logical, other phones have been doing it for quite a while (HTC's been doing it since last gen) and even pros with real cameras will fire quick bursts during a shoot to then pick the best one... How's it a battery drain if you can turn it off and the stream is probably going thru the processor at all times anyway... Now, automatically combining them in a pseudo always on HDR mode would be a different story and that would probably take a bit of a battery penalty as it's processed. Reply
  • Krysto - Friday, September 13, 2013 - link

    I'm very skeptical about the 2-led flash - at least Apple's implementation of it. To me some of those demo pictures looked like they had the colors very off. They might've been "richer" or whatever, compared to normal flash, but still looked very off to me. We'll see

    But yeah the 120fps is something other phones can do too. G2 could've done that too, but for whatever reason they picked 1080p@60fps instead - only.
    Reply
  • akdj - Friday, September 13, 2013 - link

    Are you an actual photographer? After now my third response to your comments, I'm beginning to A) Doubt the condition of your display/monitor on your computer...>B) Doubting your understanding of photography, period...and C) why in the WORLD you're injecting doubt into an extremely well written review by an ACTUAL photographer???
    Do you have some sort of objective here or a goal of some type?
    The iPhones have traditionally had excellent cameras for some time now---and continuous updates, upgrades to their subsystems, sensors, and the processing have been welcome. Hard to read your silly comments that completely go against what a professional photographer has concluded.
    Don't worry---if you bought an S4, you've got a decent camera. It's OK for others to have good ones too! In fact---as far as online posting of pics; Facebook, Twitter, Flikr----they're all dominated by iPhones as the #1, 2 and 3 'most used' cameras for shots taken. Hard to argue with that...not to mention the now iPhone-ography events, studios and....well, you get the point. They've taken on a life of their own and absolutely devastating the sales of compact point and shoot cams.
    Reply
  • nerd1 - Friday, September 13, 2013 - link

    Let me know when iPhone allows me to do exposure compensation, let alone setting ISO and color temperature. Lomo is also popular and may take impressive pictures but it never makes a good camera. Reply
  • heishin - Monday, September 23, 2013 - link

    camera+? EV compensation. WB could be locked, but not set, yet you could use that option to achieve the desired effect if you know how. Won't let you set ISO though. Again not see it as a problem as camera will always try to use the lowest ISO for given conditions. IMO your point is moot, not everyone need these options on point and shoot camera, they slow you down. And if you are really need and use them then most likely you shooting in RAW, and that's a whole other territory. Reply
  • The Saint - Friday, September 13, 2013 - link

    "Shorter focal length has generally been a tradeoff for a while to decrease the z-height of the module further, and you see a lot of smartphone vendors hovering around 28mm or slightly lower, which is relatively wide. Marketing will then turn around and market the wider angle like it’s some positive thing, which is hilarious. Apple has thus far been steadfast at staying around 30mm, but there’s no denying that the 5S will indeed be a bit wider angle than the 5 in practice. Ideally I’d love to have a smartphone module with around a 35mm focal length in 35mm equivalent numbers."

    35mm is a very narrow field of view for a modern point-and-shoot, particularly on a smartphone. A substantial portion of the pictures taken with smartphones are going to be of people indoors in close quarters, where a wider angle is immensely helpful. If a smartphone I was interested in had a 35mm equivalent, I'd actually be very disappointed.
    Reply
  • trane - Friday, September 13, 2013 - link

    Absolutely agree. 35mm is far too limiting. This is where Nokia got it spot on with the Lumia 1020 - 25mm is the sweet spot for detailed wide shots. Of course, you can zoom in to cut down the field of view, but there's no way you can get a wider image on a longer lens like 35mm.

    Also, the important thing about the "bigger pixel size = better picture" spiel is that it comes with a huge caveat - only if the sensor technology is identical. The best example in the professional world is Arri Alexa versus Sony F65. Despite 3x smaller pixels, the F65 produces usable pictures at ISO 6400 with 14 stops of dynamic range while the Alexa struggles at ISO 1600. The other thing is with higher resolution, the relative noise is much more organic. Which is why the Lumia 1020's 5MP oversampled pictures look stunning at high ISO, despite a lower pixel pitch. In short, bigger pixels is not always better. The important thing is to hit the sweet spot between sensor size, pixel pitch and sensor tech.
    Reply
  • trane - Friday, September 13, 2013 - link

    Having said all of that, at the ~1/3" sensor size, 1.5um and 8 MP is quite possibly the sweet spot given today's tech. Reply
  • Krysto - Friday, September 13, 2013 - link

    I disagree. Lower resolution gives brighter photos in low-light, but 13MP gives significantly more details, from what I've noticed, and I think 13MP with OIS > 8MP with no OIS for low-light, while being much better in good lighting conditions in terms of image quality.

    So it may have been the "right trade-off" for Apple this time around, since 13MP without OIS would've been too bad in low-light for them, but overall it's not the best choice. 13MP with good OIS is the sweet spot between image quality and good low-light performance.
    Reply

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