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Secret behind the Nokia 808 PureView camera

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Nokia 808 PureView Smartphone became one of the main attraction in MWC 2012. This is not surprising – we’re used to seeing in mobile devices 5, 8 or 12 megapixel camera. Therefore, the output of smartphone with 41 megapixel camera breaks down stereotypes.

Anyone familiar with digital photography knows that in itself is a resolution of 41 MP is overkill. Even print A3 photo-quality image is sufficient made with a resolution of 5 megapixels. But in the solution from Nokia is not about capturing images of high resolution. Debuted in the Nokia 808 Technology and received the name PureView Pro – is an attempt to improve the image quality is at the expense of an edge over competitors.

Nokia 808 PureView

Regardless of the technology used the basic principle remains the same photograph – the light passes through the lens and falls on the sensor. In the case of digital photos – a sensor matrix. The number of captured light is determined by the size of the sensor and lens. To capture a larger number of photons needed a bigger sensor and a greater distance between the sensor and lens by lens.
Because of the limitations of dimensions in mobile phones are usually used compact camera module equipped with a small sensor with a small distance to the lens. By increasing the size of the sensor, respectively, need to increase in proportion to the distance between him and the optics. The size of the sensor Nokia 808 – 1/1.2 inch, which is less than that of compact cameras, but more than most smartphones. Moreover, the desire to compact device makes it impossible to use in mobile devices, complex optical circuits. And this is the fundamental difference between smartphones from compact cameras.

The maximum effective resolution camera module Nokia 808 is 38 megapixel photography with a 4:3 aspect ratio and 34 megapixel shooting in 16:9 format. Moreover, it is a crazy number of megapixels has a relatively compact sensor. However, Nokia does not go by simply increasing the resolution of pictures, and find other uses for these pixels, reducing the picture resolution in the settings “default” to 5 megapixels and using pixel oversampling (resampling points). Thus, by its resolution of photographs made by Nokia 808 PureView does not differ from the images made by other smartphones, but at the expense of “oversampling” of the company failed to effectively suppress the noise, while maintaining “virtually all the details” and not making a shot in the extra distortion.

Zoom

A further advantage of oversampling – the possibility of implementing digital zoom in photo without making the interpolation distortion. As we mentioned, the use of classical optical zoom increases the overall dimensions of the lens. Therefore, for mobile devices is the support of a traditional digital zoom. But, when the classical scheme of the digital zoom is used a smaller piece of the camera sensor, and the desired resolution images obtained by interpolation. The result – the deterioration of the quality and increase noise in the picture. The decision by Nokia more elegant – using just a digital zoom decreases the number of points averaged for oversampling. When maximizing the oversampling is not used at all, but from the resulting images with the camera’s sensor just cut out the fragment permission.

Thus, excluded the use of interpolation, and image quality made by Nokia 808, even with the maximum increase would be no worse than what other phones equipped with camera module of a similar resolution. Of course, when using digital zoom, the Nokia 808, respectively, reduced the physical area of ​​the site sensor, which produces a picture, but still the image is “real.”

Nokia is absolutely justified claims about the benefits of the camera Nokia 808 with respect to compact digital cameras, is to prevent vignetting (darkening at the edges of the image frame) and the distortion caused by the glass lens and a digital correction. In addition, the Finns say that even at the highest magnification remains aperture F/2.4, because the way the world does not introduce additional obstacles. However, the fact that Nokia extols the presence of a constant F/2.4 and “authenticity” of the image is not surprising. While varying the aperture and shutter speed, using a digital camera to make high-quality images even in low light conditions and quite realistic.

Another thing is how the technology PureView Pro copes well with the needs of mobile photography? As far as Nokia is well managed to avoid problems when shooting in low light conditions? How effective is using a flash? Does oversampling sufficiently “clean” result? Does the cut portion of the image obtained using the maximum increases, high-quality picture? Of course, Nokia cited examples of images look good. Will everything just as well when the Nokia 808 will fall into the hands of reviewers and users? Of course, now phone camera with 41 megapixel is pretty unusual. But in the marketing of Nokia 808 does not permit a manufacturer promotes as such, but rather how it is used.

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