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What is PureView Pro Technology?

29 Feb , 2012  

 

On this 27th, Nokia announced its first device with PureView technology, Nokia 808 PureView, having 41 MegaPixel camera and everybody are just WOW! Well, that’s obvious. Even, how many would have expected this thing in a Mobile Phone? Surely very few, who are behind PureView Pro technology. But what is this PureView Pro technology? Many of you who may be unaware about this. Nokia have already released White Paper written by Juha Alakarhu, Damian Dinning, and Eero Salmeli for PureView Pro technology. Let’s try to understand it.

What is PureView Pro Technology?

Let me quote the white paper definition:

The Nokia PureView Pro imaging technology is the combination of a large, super high resolution
41Mpix with high performance Carl Zeiss optics.
PureView Pro imaging technology doesn’t represent a step change for camera smartphones performance, so much as a quantum leap forward. The first device to feature Nokia PureView Pro camera  technology is the Nokia 808 PureView, which gives people the means to take better images and video footage than ever before.

Camera Specs

Nokia 808 possess  a super high resolution sensor having active sensor area of 7728 x 5368 pixels, more than 41MPixels. For 16:9 aspect ratio, it uses 7728 x 4354 pixels and  7152 x 5368 pixels for 4:3 aspect ratio, that means about 38MP at 4:3 aspect ratio, 36MP at 16:9. It has 1/1.2″ sensor which is almost three times the size of the sensors in most compact cameras which will give you much better quality.

Nokia 808 PureView lens and sensor specifications

  • Carl Zeiss Optics
  • Focal length: 8.02mm
  • 35mm equivalent focal length: 26mm, 16:9 | 28mm, 4:3
  • F-number: f/2.4
  • Focus range: 15cm – Infinity (throughout the zoom range)
  • Construction:
    • 5 elements, 1 group. All lens surfaces are aspherical
    • One high-index, low-dispersion glass mould lens
    • Mechanical shutter with neutral density filter
  • Optical format: 1/1.2”
  • Total number of pixels: 7728 x 5368
  • Pixel Size: 1.4um

Why do we need 41 MP camera?

This question is obvious. 41 MP for a mobile phone camera will look an overkill. Well, surely, no one need 41 MP images. Then why 41MP? With 41 MP sensor, we have 41 million pixels of image. Greater data means we will have more details for processing. Ideally 5 MP images are enough for normal photography. With large 41 MP sensor, pixel oversampling is possible which enhance the details of images and creates 5MP image.

What is Pixel Oversampling?

It’s a geeky term, and you may be confused about it. Each image is made up of pixels and a pixel can have only single color. We assign a color to a pixel. For a true 5MP sensor, we will assign the color captured from the sensor’s pixel. Whole view is just in 5MP. But with 41 MP, we have more pixels. In oversampling, we uses neighbouring pixels to create a super pixel. Suppose with 41MP, we use 7 neighbour pixels and assign an average color to the super pixel. Thus, we get more accurate color for a pixel. Thus resulting 5MP image from a 41MP image is much more noise free and realistic than we may have got with a 5MP sensor.

Pixel oversampling combines many pixels to create a single (super) pixel. When this happens, you keep
virtually all the detail, but filter away visual noise from the image. The speckled, grainy look you tend to
get in low-lighting conditions is greatly reduced. And in good light, visual noise is virtually non-existent.
Which means the images you can take are more natural and beautiful than ever. They are purer, perhaps
a more accurate representation of the original subject than has ever been achieved before
oversampling eliminates Bayer pattern problems. For example, conventional 8MPix sensors include only
4Mpix green, 2Mpix red and 2Mpix blue pixels, which are interpolated to 8Mpix R, G, B image. With pixel
oversampling, all pixels become true R, G, and B pixels. What’s more, based on Nyqvist theorem, you
actually need oversampling for good performance. For example, audio needs to be sampled at 44 kHz
to get good 22 kHz quality


How does Zoom works?

As white paper says:

Nokia PureView Pro turns conventional thinking
on its head. It dispenses with the usual scaling/
interpolation model of digital zoom used in
virtually all smartphones, as well as optical zoom
used in most digital cameras, where a series of
lens elements moves back and forth to vary the
magnification and field of view. Instead, we’ve
taken a completely new road.
When you have Optical Zoom in a camera, camera module becomes bulky because it needs a mechanism to move camera lens relatively to get magnification. While in Digital Zoom, image is upscaled which will bring noise and low details. In PureView, we have different approach. So how does this zoom work? In PureView, we have 41MP sensor. With 5MP shooting mode, when you zoom, what actually happens is only relevant area of sensor is used. That means, we don’t use full 41MP sensor but some center part of sensor depending on zoom. We are actually cropping the sensor. But this will mean we will have less pixels for oversampling. Quality will reduces a little than we would have without zoom, however, achieved quality is without any loss of detail. Zoom limit comes when with 5MP shooting mode, selected sensor are becomes 5MP. In this case, we won’t have pixels for oversampling. However, remember, we are not losing details that we may have lost in Digital Zoom. Hence, we always have true image.
The size of the Nokia 808 PureView camera (including sensor and optics) is at least 50%-70% smaller
than a conventional optical zoom design.
This mechanism for zooming brings another advantage, silent and fast zoom. They don’t use optical elements’ movement for zoom, so it’s faster and silent.

Lesson Learnt From Nokia N8

With the 12Mpix Nokia N8, for example, we were more concerned with capturing photons of light than
ramping up the number of megapixels. We bucked the trend and went with a large sensor and 1.75
micron pixels — but the result was a new benchmark in image and video quality. This set the Nokia N8
apart at the time, and competitors are still trying to match it two years later. The Nokia PureView Pro
comes is equipped with an even larger sensor, 1/1.2” approximately 2.5 larger than the sensor used
in the Nokia N8. The result is an even larger area to collect photons of light. With PureView we’re
continuing to make choices focused on performance rather than pixels for pixels’ sake. Fewer but
better pixels can provide not just better image and video quality, but better overall user experience
and system capability


Wrap-up

I think, I have explained enough to clear what PureView Pro Technology is. I am not camera or computer graphics expert, but I tried to explain all the stuff accurately to my best knowledge. I will really love to read your thoughts on  this. Also, please share your knowledge in comment or on Twitter @NokiaTips

Reference

PureView Imaging Technology Whitepaper: http://europe.nokia.com/PRODUCT_METADATA_0/Products/Phones/8000-series/808/Nokia808PureView_Whitepaper.pdf.

You can also have a look at the whitepaper for more details or the sections I didn’t cover. :)

 

Kishan Gor is a Co-Founder of NokiaTips. He is Software Developer by profession and have a great passion for Programming and Gadgets.

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