Nokia 808 PureView

The Nokia 808 has a 41.3 megapixel 1/1.2 in CMOS FSI image sensor with 7728×5368 pixels, built by Toshiba and branded HES9.[21] Pixel size is 1.4 µm;[21] sensor size is 10.67 × 8.00 mm.

Depending on the aspect ratio chosen by the user, the sensor will use a maximum of either 7728×4354 pixels (33.6 MP; full sensor width) for 16:9 images, or 7152×5368 pixels (38.4 MP; full sensor height) for 4:3 images[21] when using the default camera software, although third-party apps exist that can capture the full resolution of the sensor. The output from the sensor is processed using the on-chip image processor, resulting in a lower-resolution final image with a default resolution of 5 MP through pixel binning (oversampling) from the full 34/38 MP image. The image processor highly reduces external processing needs and data rates as well as image noise (see noise shaping). The pixel binning was non-destructive, meaning the user could reframe the image or zoom in after the shot was taken.[21]

Zoom is digital, meaning the image is cropped from a smaller portion of the image sensor, with a corresponding reduction in the level of pixel binning as the zoom is increased. In general, the camera of the 808 retains a high resolution even when zoomed in, due to the 41 MP sensor. The limit of the zoom is reached when the selected output resolution becomes the same as the input resolution. That means once the area of the sensor reaches 3072×1728 (5 MP for the 16:9 aspect ratio), the zoom limit is reached. At default settings, maximum zoom is 3× for stills and 4× for video (1080p).[21]

The zoom always provides the true image resolution the user wants. The amount of pixel oversampling is highest when zoom is not used. It gradually decreases until the maximum zoom level is reached, where there is no oversampling. At this stage, PureView Pro optics and pixels start behaving in a more conventional way. But because only the centre of the optics is used, the best optical performance is achieved – including low distortion, no vignetting and highest levels of resolved detail. This also means that at full digital zoom, the noise reduction achieved by oversampling (pixel binning) is lost as no oversampling happens at full zoom.

The 808 PureView compared to its successor, Lumia 1020

PureView Pro features continuous autofocus in all shooting modes, close-up (Macro) focus, face detection, touch focus with easy manually selected focus point and hyperfocal distance focus for defined depth of field, for extreme focus speed or when reliably achieving focus is not possible.

The on-chip oversampling image processor of the 808 enables oversampling of all 38 megapixels even at the high video data rates of 1080p with 30 fps. Maximum possible zoom is 4× for 1080p, 6× for 720p HD and 12× for nHD (640×360) video. In addition, encoding is up to 25 Mbps in 1080p H.264/MPEG-4 HD video format. The PureView Pro sensor integrates a special video processor that handles pixel scaling at up to 1 billion pixels per second[22] before sending the required number to the main image processor.

The camera of the 808 has a very large and noticeable hump

The 808 has Carl Zeiss 5-element lens with f/2.4 aperture and 8.02 mm focal length (35 mm equivalent focal length is 26 mm in 16:9 and 28 mm in 4:3 aspect ratio). Focus range is from 15 cm to infinity (throughout the zoom range).

The optics are based on a shiftable fixed-focus lens; similar to the prime lenses in most Zeiss Planar or Tessar optics, focus is achieved by varying the distance to the image sensor (unit focusing lens). This construction has the advantage that no movable focus group is needed. Considerable movable (focus-range) lens groups need a minimum of one additional adaptive lens element in both the moved group and the stationary group, increasing the number of elements by at least two. This increases unwanted reflections as well as overall tolerances and therefore decreases sharpness.

The lens consists of only 1 group with molded elements, which gives a highly stable, precise mechanical alignment. The lenses are partly made of plastic, which provides sufficient stability at this size and as a 1-group lens and has the significant advantage of making it possible to use extreme aspheric shaped lens elements.[23]

5 all-aspherical lens elements are used, making it possible to increase border-sharpness and lower distortion and astigmatism. The high–refractive index, low-dispersion glass additionally helps reduce chromatic aberrations. A neutral density filter with approximately ND8 (3 f-stops) is employed for shooting in high light levels where normally a smaller aperture would be set. Although the lens is named a Tessar, it has almost nothing in common with the 4 element in 3 group, non-aspherical original Tessar.

Due to the comparatively large 1/1.2 in sensor and the comparatively fast lens with f/2.4 aperture, the camera has a quite shallow depth of field, equivalent to approximately f/7.8 at 26 mm[24] on 35 mm full-frame.

The 808 has a mechanical shutter with short shutter lag[22] and ND8 (3 f-stops) neutral density filter.

The 808 PureView employs Dolby Headphone software to transform stereo content to surround via a 3.5 mm A/V jack. It also includes Dolby Digital Plus software to provide 5.1 surround sound via HDMI or DLNA. The dual software elements from Dolby are embedded into the Nokia Belle feature pack 1 OS.[25]

The 808 PureView is the first device to include the Nokia Rich Recording technology and has a frequency range between 25 Hz to around 19 kHz. The 808 PureView can capture sounds at the loudness level of up to 145 decibels without distortion. The two microphones, located at the top and the bottom enable ambient stereo recording. The audio encoding is done in AAC high profile, 256 kbit/s, 48000 Hz.[26]