In terms of mobile imaging, the
Nokia 808 is a revolutionary device. Not only is it capable of taking images of
up to 38MP, but it can also make use of a technology called oversampling, which
means that out of several pixels of information it captures, it outputs to
memory a single resulting pixel, which hopefully, is picture perfect.
There are three direct advantages to
this oversampling technology: amazing image quality, lossless zoom, and
superior low light performance.
Maximum
resolution matters
The Nokia 808 can capture 4:3 images
at up to 38MP and 16:9 images at up to 34MP. The sensor size at 1/1.2″ is
impressive, and is more than double the one found on the N8. And if you gotta
know, that means an estimated pixel size of 1.26 microns, as opposed to the
1.75 micron sized pixels on the N8.
Yes, the 41MP sensor of the Nokia
808 is impressive, but as evident from the above, you won’t be able to take
41MP photos. Here you can see all the different image aspects and their
respective resolution. The sensor has a total active surface of 7728 x 5368
pixels, which does amounts to 41MP, but depending on the aspect ratio you
choose, it will use either 7728 x 4354 pixels for 16:9 images or 7152 x 5368
pixels for 4:3 images/videos.
Actually, the default shooting mode
for the camera is 5Mp in 16:9 aspect ratio. But you also get other options as
well, including a full-res mode.
Pixel
oversampling is like miniaturization but prettier
But enough about maximum resolution,
let’s get back to image quality. The Nokia Team have spent a lot of thinking on
how to improve the image quality on size-constrained mobiles. With pixel sizes
ever decreasing, the challenge for engineers is quite clearly to overcome the
negative effects of this, which are high digital noise levels and the resulting
poor low light performance. Enter pixel oversampling.
Oversampling is different from mere
cropping as it doesn’t simply use part of the sensor to produce a lower
resolution image. Instead, it still uses the full sensor, but downsizes the
resulting image to say, 5MP on the Nokia 808. The benefit of this is that this
process of downsizing removes digital noise, while preserving the same level of
detail you might get by shooting with the best 5 megapixel camera.
But there’s more to having such a
huge sensor.
And
it goes all zoom-zoom
Since the Nokia 808 captures so many
pixels and is able to produce lower res photos, it’s only natural that it tries
to tackle one of the other most wanted features in cameraphones – the lossless
zoom. Instead of focusing on the traditional ways of delivering image zooming
such as digital interpolation or optical magnification, the Nokia team has
embarked on incorporating the highest resolution sensor ever found on a mobile.
Everybody has tried regular digital
zoom, it’s no good. Some have even attempted optical zooming, but it’s way too
bulky, noisy and even slow and introduces geometrical distortion. The only
viable solution was the 2x digital zoom that was offered by the N8 in video
mode (via pixel binning) but even that had some sort of an interpolation. But
to be able to offer any zoom levels in still images, you need to have a solid
sensor with a huge amount of extra pixels compared to the nominal output
resolution. And lots of processing power.
To cater for the immense processing
requirements (over 1 billion pixels per second and 16x oversampling), the Nokia
team has developed a special companion processor to the sensor that handles
pixel scaling before sending the required number to the main image processor.
Once that’s out of the way, you get
lossless zooming with the same effective viewing angle – in 35mm equivalents,
it’s 28mm in 4:3 aspect ratio and 26mm in 16:9. And depending on the
resolution, you get varied amounts of zoom levels. In 5MP stills, for instance,
you get around a 3x zoom.
I’ll let the Nokia team deliver
their explanation of this new zoom method, they simply nail it in rather simple
words:
With the Nokia 808 PureView, zoom is
handled completely differently — like nothing that has gone before. We’ve taken
the radical decision not to use any upscaling whatsoever. There isn’t even a
setting for it.
When you zoom with the Nokia 808
PureView, in effect you are just selecting the relevant area of the sensor. So
with no zoom, the full area of the sensor corresponding to the aspect ratio is
used. The limit of the zoom (regardless of the resolution setting for stills or
video) is reached when the selected output resolution becomes the same as the input resolution.
For example, with the default
setting of 5Mpix (307 2 x 1728), once the area of the sensor reaches 3072 x
1728, you’ve hit the zoom limit. This means the zoom is always true to the
image you want.
The level of pixel oversampling is
highest when you’re not using the zoom. It gradually decreases until you hit
maximum zoom, where there is no oversampling.
Here’s an example of the amazing
level of detail the Nokia 808 allows with its high-res shots.
In video, at FullHD 1080p resolution
you get a 4x lossless zoom, at 720p HD video you’ve got a 6x lossless zoom, and
for nHD (640×360) video there’s the option for some serious12x zoom. And you
can bet video quality will be great, since the 808 encodes the video in up to
25Mbps worth of bitrate.
The
Nokia 808 camera has some other impressive specs too
Even without these amazing,
never-before-seen-in-a-mobile features, the Nokia 808 has some serious imaging
potential. You’ve got a Carl Zeiss certified lens, a relatively large F2.4
aperture, and a Neutral Density filter for those high-intensity lighting
situations.
The added mechanical shutter
minimizes the disadvantages of the implementation of a rolling shutter such as
the vertical stripes that appear in the highlights of high-contrast images also
known as smear, as well as the wavy “Jell-O” distortion that sometimes appears
if you move the camera while shooting.
Also, the large sensor size and the
longer focal range of 8.02mm in combination with the large aperture delivers
more blurry background in closeup shots as opposed to most regular
cameraphones, which is exciting on its own.
Wrapping
it up
As Nokia puts it, the Nokia 808
presents a “quantum leap forward in cameraphone performance”. Indeed, it
introduces concepts we’ve never thought possible on a mobile phone. It’s not
about the piles of megapixels but rather what you can do with them, such as
producing picture perfect low-res images or lossless zooming in both stills and
videos (including after-the-fact zooming and cropping). It’s one helluva camera
and we bet it will be able to challenge most point-and-shoots on their own
turf.
