Home Microsoft "PureView" The Second Phase – In Lumia, It’s not what you have thought but it’s still amazing.

"PureView" The Second Phase – In Lumia, It’s not what you have thought but it’s still amazing.

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Putting simply to the context we have seen in recent days, Nokia’s PureView technology was not about a hard and fast rule to apply with giant sensor to achieve loss-less zoom, greater detail in image quality and reduced digital noise in low-light conditions. Instead with Windows Phone 8, Nokia brought the PureView with another perspective which is not the same as we have seen on Symbian powered Nokia 808 PureView.

What we should call the “PureView” thing? If I remember, It was the technology or a technique of using huge sensor with a lot pixels for oversampling and making a one pure pixel? May be it was like that at some earlier stage but now. No! it’s not. Now it’s a set of different technologies that actually are meant to bring quality photographs by “whatever” mean and not only by pixels “oversampling”. That’s the concept, Nokia has built up for consumers to accept the Windows Phone 8 devices when they come with a label “PureView”. That could be, in someway, a good idea to define “PureView” to build up for later devices (for marketing) because, first; an already understood factor is that the consumer preferable slimmer device could not have that much space to accommodate huge sensors. Second; The Windows Phone 8 is not “yet” capable of processing those much megapixels on a huge sensor that a Symbian smartphone has done. No doubt that Nokia 808 PureView has set up completely a unique benchmark for smartphone devices, however Nokia did really a good job to figure all the things for its new dedicated Windows Phone 8 platform and has managed to bring the things right on the consumers’ demands. Last but not the least, it still stands out of the crowd for its own “PureView” capability.

Whilst some may associate the PureView moniker with specific features, specifications or functionality introduced along with the 808 PureView, Nokia’s ultimate intent for PureView is to be synonymous with high performance imaging. We deliver our flagship imaging technology through a set of industry leading imaging technologies, rather than a single element, feature or specification. As time goes by, this will be especially important as PureView becomes greater than the sum of its parts.

Disclaimer: This article is completely based on the official whitepaper released by Nokia to explain the things working behind Nokia Lumia 920’s PureView powered camera. In the following text I’ll be picking up the major points from the whitepaper and telling my opinion on them. This must not be considered as an advertisement attempt or a promotional editorial(advertorial) for Nokia from me or from Tech Prolonged at all. We are not promoting the product in subject, however trying to understand and give a wider idea what the company has brought in their flagship product and has described in an official document. – our final verdict is added in final paragraphs –

Let’s start with a photo taken with Nokia Lumia 920, as said responsibly by Nokia. Well that’s really a impressive night shot.

lumia-920-proto-shot-1

Now what the Phase Two of “PureView” (PV2 or PureView 2 will be used from now on) technology has brought to the Nokia Lumia 920? On what photography factors PureView 2 is focusing if that’s not the loss-less zooming and detailed image quality? The answer is the huge improvement in “low-light” conditions which at some extent was also present in Nokia 808 PureView.

If revising a bit, Nokia 808 PureView actually used a “solution” of oversampling along with a bigger sensor to improve image quality and added features like loss-less zooming in most of the aspects also including in “low-light” conditions. With PureView 2, Nokia adopted another direction – “a different solution” – to bring that quality (not that much quality what 808 PureView did and no loss-less zooming, mind it.) with smaller sensor as per the requirements in a slimmer device but sure it did bring brilliant night-shots even more impressive than 808 PureView has done.

Depending and restricting by the requirements, instead of the large sensor Nokia worked with the combination of “large aperture”, BSI (Back-Side Illuminated) sensor, OIS (Optical Image Stabilizer) and new image processing algorithms.

What is it about 8.7MP camera?

The 8.7MP specified in Nokia Lumia 920’s specifications is actually the camera sensor resolution but that’s not what you get from the camera. The maximum effective resolution is 8MP when shooting at standard 4:3 aspect ratio or 7.1MP when shooting at wider 16:9 aspect ratio. These are the standard aspect ratios but Nokia used an oversized sensor to give you the most of the effective resolution at either of the aspect ratios.

For instance, just like in Nokia 808 PureView, the sensor in Lumia 920 is quite larger than the image projected on it through the lens. And the reason is again same why Nokia has chosen a custom oversized sensor instead of what’s used by other manufacturers. That’s to achieve true 16:9 aspect ratio which snaps the picture at the bigger 7.1MP resolution when cropping from an oversized sensor of 8.7MP instead of the ordinary exact 8MP sensor that gives only 6MP shot at the 16:9 aspect ratio. The following figure illustrates the sensor in Nokia Lumia 920.

nokia-lumia-920-8-7MP-camera-sensor-diagram

In simple words the 16:9 aspect ratio achieved by this method gives you larger resolution than the one that’s cropped from ordinary 4:3 sized sensor of 8MP. What that means is you get wider field-of-view in horizontal as around 26mm equivalent unlike the 28mm via the 8MP sensor.

What’s the buzz about OIS in Lumia 920?

If you are not familiar with enhanced and pro photography features which are the key elements in compact digital cameras if available and in most of the DSLRs. What it does is specially to avoid camera-shake issues mostly when shooting handheld for better pictures without blurry movements in main subject in both either stills or videos. In a process of optical stabilisation the lens element moves in the opposite direction to what the device moves to. It’s all performed to compensate for unintentional movement caused by camera shake which effectively at most extent does the job.

lumia-920-proto-shot-2

Just like, it was the “monster 41 megapixels sensor” in Nokia 808 PureView, the “Optical Image Stabilisation” is now the biggest element in Nokia Lumia 920 to be appreciated. And that’s also the first time ever, the optical stabilisation is being equipped into smartphones. But Nokia has something to be proud of, mentioning that they have been successful in outperforming the typical OIS in most digital cameras, with the Carl-Zeiss featured “floating lens” technology for image stabilisation.

Rather than a single lens element being shifted to compensate for camera shake, Nokia’s OIS system moves the entire optical assembly in perfect synchronisation with the camera movement, or to be more precise, unintended camera shake. The benefit of this approach is that the amount and form of camera movement that can be compensated for is much greater.

Nokia has also claimed in the whitepaper, that the new OIS system can cater 50% more movements per second than the conventional OIS systems in most digital cameras – that’s up to around 500 movements per second- by monitoring the position of the lens assembly in real time no mater at what rate/interval the camera is moved.

This process of checking operates at a rate of up to 5x more frequently than typical OIS systems, approximately 300 times faster than that of the average human reaction time to an expected event.

Claiming that Nokia’s OIS system can compensate with camera shake in low-light conditions to even lower lightening levels than conventional OIS systems. Nokia also puts a reference point from photography basic facts about how much ability, at average, a user does have to hold the camera still. That is, the shutter speed slower than 1/30th second can result in a camera-shake when hand-holding the camera. Nokia claims that in their OIS as long shutter speed can be used as 1/4th second. That’s around 8 times longer shutter speed or exposure compensation improved by 3EV. – Well if that’s true, I believe it’s a tremendous achievement in smartphone photography –

nokia-lumia-920-ois-lab-test-chart

Not only still photography is helped by the optical stabilisation, the video recording also uses the feature for smooth movements avoiding the unintentional camera-shake.

Following official sample is showing the OIS engagement while recording the video on Nokia Lumia 920 along side the clip record with a non-OIS featured device.

BSI Sensor & Larger/Brighter Lens Aperture

As already pointed out about the replacement of the huge 41 megapixels sensor and using the smaller 8.7MP sensor instead in Lumia 920, as said by Nokia, was the most challenging opto-mechanical design to date for the company. Those challenges of course made Nokia to work with all those elements including the OIS to improve image quality for consumers in the smartphone.

BSI (Back-Side Illuminated) sensor is the part which has also played its role in this new phase of PureView. The main purpose of BSI sensors is to deliver more light helping increase image quality in low-light conditions and have been widely used in smartphones including from Samsung, HTC and Apple as well as digital cameras have been using BSI CIS for quite a long time now. But Nokia, in the PureView 2 whitepaper, has mentioned about the issues found in early BSI sensors, hence using the latest generation of BSI sensors where those issues have been overcome.

Nokia Lumia 920 is equipped with the 1/3” type sensor with the pixel size of 1.4µm, that is around 4.8×3.6mm in dimensions and again is a little bit larger than the standard 1/3.2” type sensor commonly used in most of the mobile phones. Plus the f/2.0 lens aperture is much larger than found in any other high-end smartphone. Nokia 808 PureView was also lacking on this part while having only f/2.4. However HTC in the those days brought the f/2.0 lens aperture in the HTC One S and HTC One X. Those smartphones by HTC were also in the league of photography having dedicated on-board imaging chip. Well practically those smartphones couldn’t come closer to Nokia’s monster 808 PureView, frankly. We’ll really want to see if Nokia Lumia 920 will surpass 808 PureView’s low-light performance when it will come into the consumers’ hands. No doubt the official samples of Lumia 920 provided by Nokia were really superb in the respective low-light conditions, I believe those must have been in high-resolution (on flickr perhaps like they did with Nokia 808 PureView?) Take two more samples from Nokia Lumia 920’s prototype device below.

ApolloPureView-image-1 ApolloPureView-image7

Photography Device from Nokia but no Xenon Flash?

It’s one of the questions one most probably will ask about Nokia Lumia 920. Nokia has always shipped its camera centric devices with sexy Xenon flash units that never failed in any of those devices when shooting with flash. While Nokia has also shipped devices with LED flashes which, truly speaking, I never liked the result they delivered specially the latest ones e.g. Nokia Lumia smartphones and Nokia N9 also. However due to Carl Zeiss optics they always worked awesomely but without flash. In fact, LED or Dual LED flashes in smartphones from Nokia’s competitors were more brighter as far as I have experienced – never surpassed the excellence of Nokia’s Xenon flashes though.

But “same” Nokia, now when they have to work with slimmer devices along with Microsoft’s Windows Phone, just like taking another direction for “PureView” has decided to take the route of LED flashes. In fact explaining about the performance of next-gen LED flash that’s now increasing over the xenon. Just like introducing latest generation BSI sensor above, again Nokia used just two words “Next Generation” to introduce another element that is the LED flash.

To bolster the low light performance, we’re introducing a new generation LED. It provides the benefit of being able to be used as a continuous light source e.g. for video or as a highly popular secondary function; a torch and now for the first time – a pulse flash burst.

Nokia, however, accepting the power of xenon flash being short burst lighting source in the same document is mentioning that their new generation LED flash although is not as short as xenon flash but is enough better than conventional LED flashes to provide sharper picture of moving subjects.

Nokia’s Imaging Algorithms and the part of Microsoft in PureView

At the time of launch, where Nokia was explaining most of the bits about the new Nokia Lumia 920 and the “PureView” technology it’s built with, Joe Belfiore a key executive in Windows Phone design team from Microsoft gave the demo of a new imaging framework and apps introduced in Windows Phone 8 that work in very unique and distinctive way with Nokia Lumia 920’s camera capabilities. Nokia’s proprietary image processing algorithms are integrated into the Windows Phone 8 imaging framework. Nokia’s whitepaper also has disclosed the “denoise algorithm” for reducing visual noise.

Windows Phone 8 introduces a new imaging framework which allows the heavy integration of Nokia’s wide range of image processing algorithms including autofocus, auto exposure and auto white balance, to name just a few. But these don’t even scratch the surface of what’s new in Windows Phone 8 from Nokia.

One of the most important new algorithms is our new denoise algorithm for reducing visual noise, which helps to further improve low light performance while keeping the image very natural.

Lens and Sensor Specifications

  • Sensor: 8.7Mpix BSI – 1/3″ type sensor – pixel size 1.4µm (1.4 microns)
  • Carl Zeiss Optics with Barrel Shift Type Optical Image Stabiliser
  • Stabiliser Performance up to 3EV (8x longer shutter speeds)
  • Focal Length is 3.73mm
  • 35mm equivalent focal length is 26mm at 16:9 and 28mm at 4:3 modes.
  • Aperture f/number: f/2.0
  • Focus Range: 8cm to Infinity
  • Construction: 5 elements, 1 group, All lens surfaces are aspherical.

What to expect from this phase of PureView?

I already have said in many of my tweets (@khurramar) as well as have mentioned in various posts that what people had been anticipated to have that “PureView” in Windows Phone devices or Lumia devices from Nokia can never (or at least till today) be like the one they have seen in Symbian powered Nokia 808 PureView. There were many reasons for that but the major one was the accommodation of optical elements. It’s human nature that they want everything at everywhere. We need that impressive 41 megapixels camera with all those awesome features of “PureView” but we don’t want the bulkier device. We like what the device does, but we don’t like the operating system in it who actually does that.

It’s a really appreciable job Nokia has done to fulfill consumer’s demand no matter at what extent but they did it the other way if not evenly with previous “PureView”. In fact introducing the optical image stabilisation first time ever in a smartphone is a big achievement that even was not present in the previous “PureView” smartphone. As per the specifications detail above and the video sample the OIS seems to perform well in Nokia Lumia 920.

With all that, This smartphone couldn’t make that big impression to me which 41 megapixels 808 PureView did at the first time, however I am evenly anticipated to try the new “PureView” capability in Windows Phone 8 powered Nokia Lumia 920.

What do you think of all that Nokia has tried to explain? Do give your comments below and show the interest if you have.

[source PureView, Whitepape [PDF] ]

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