Is A Slimmer PureView Possible? I Look Into Some Of Those Ways


We still don’t know what Nokia has in surprise for us when it launches its new Windows Phone 8 running Lumia smartphones in less than 24 hours from now.  Nokia is known for superb cameras in its smartphones. With 808 PureView Nokia made sure that no one questions their authority when it comes to camera performance. However the 808’s camera module is too bulky and Nokia may be forced to look out for other options so that they can deliver a sleek and slim device without deviating much from the camera standards set by 808. Rumors are that Nokia Lumia 920 will have an 8MP camera and a different form of PureView than in the 808. Some people think it is impossible to achieve 808 like quality without a huge sensor, this isn’t completely true. We discuss some ways in which similar image quality can be attained by using different “design friendly” techniques:

PureView Lite

The 808 comes with the PureView Pro technology. Nokia used a large 1/1.2 inch sensor along with a large lens and xenon flash. The 808 camera no doubt gives extraordinary results but it comes at a price. The 808’s camera bulge is 18mm thick which may look awkward to some people. Although I am not a fan of anorexic phones but devices like HTC One X, Nokia N9, Xperia Arc, Nokia C7 and iPhone do catch one’s attention.
So instead of a 41 MP sensor Nokia may go with a smaller (say 1/1.7”) sensor with 20-25 megapixels. The sensor size is approximately the same as in N8 and some high end point and shoots cameras like Canon S100. The 808 combines signal from 8 pixels to produce a 5MP image. A 20MP sensor would have only 4 pixels to do so. So image quality (and noise) of a 5MP picture from this theoretical camera would be similar to an 8MP image from 808 (remember I am talking about image quality and not details. )
The interesting part about this PureView Lite theory is that the leaked Lumia 920 was supposedly codenamed Nokia phi. Someone pointed out that phi is the 21st Greek letter so it may have a 21MP camera (although it sounds silly)

Going the N8 way

The N8 is still the second best cameraphone. Nokia’s strategy with N8 was pretty simple. Large sensor = better image quality. Nokia might stick with the same 1/1.8 inch 12MP sensor or an 8 MP sensor of same size which would further improve the low light abilities of the already good camera.

Software Solution

Nokia’s camera guru has emphasized on the fact that PureView is a combination of hardware and software. The software part in 808 does the work of combining 41 million pixels to make a 5MP image. However what if Nokia sticks with the conventional 8MP 1/3.2 inch sensor used in most smartphones? If we look beyond Nokia, Samsung galaxy S3, iphone4S and Xperia S have pretty good image quality in day light. These tiny sensors however fail to impress in low light/high ISO conditions. One way to come up with low light is to use a reasonably long exposure. However this could be an issue with smartphone snappers who don’t use a tripod. Another intelligent way to do this is to take 4-6 high ISO images in quick succession and then combine them to form a high ISO image with considerably less noise. Sounds similar to PureView? Well we are combining processed images this time. This technique is used in Sony’s alpha-Nex series, Canon Powershot cameras and Some Panasonic Lumix cameras. Mind you the results are pretty good.

Graphene based Sensor

A patent suggests that Nokia is experimenting with Graphene based sensors. This tech is probably in early development phase so I wont go into details. Basically the sensor can capture twice the amount of light than conventional CMOS sensors and is also thinner and smaller allowing large megapixel small sized sensors without loss in quality expected in a similar conventional CMOS or CCD model.

Using non-Bayer sensors

Most people think that 808 produces great images because of interpolation. This is however partially true. During oversampling 808 eliminates Bayer interpolation. It packs (theoretically) thrice the detail that cam be captured by a conventional 5MP sensor of similar size. The PureView Pro whitepaper says

oversampling eliminates Bayer pattern problems. For example, conventional (Bayer)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

Hence Bayer matrix results in loss of 30-50% of the real resolving power of the sensor.  This can be overcome by using a non-Bayer sensor. While these aren’t very popular (maybe due to cost) the results are very promising. For example a Leica M Monochrome has an 18MP non-Bayer sensor but it resolves slightly more detail than the Nikon D800E which has a 36MP Bayer sensor. Note that both sensors are full frame so sensor size is not an issue here.

Better conventional technologies

One doesn’t need rocket science to produce great images. Nokia can use popular new techniques like Backlit sensors rather than conventional CMOS to enhance low light capabilities coupled with a large f/1.8 aperture for better light capture. These things can also be coupled with other models we have discussed above. Like using a BSI CMOS 21MP sensor can probably provide the same low light performance like the 41MP sensor from 808.

Looking at the negative size a smaller sensor would mean less depth of field and lesser dynamic range irrespective of whatever technology Nokia uses. There are many arguments that can be put. However as of today there is no point in discussing over things that don’t exist. :) We’ll wait and see what Nokia has to reveal tomorrow!