
Nokia Unveils Symbian 41 Megapixel Camera Phone - pbahra
http://blogs.wsj.com/tech-europe/2012/02/27/nokia-unveils-symbian-41-megapixel-camera-phone/
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Gravityloss
Hooray, in the end they can go to no pesky lens at all since image quality can
be improved infinitely by adding more pixels. Using a pinhole does away with
that focusing too. ;)

To be serious, I'm more of a physics guy. Photon "shot" (think shotgun with
fewer and fewer pellets) noise determines already the lower limit of noise and
(having a certain fixed shutter speed which is defined by avoiding movement)
the only way you get more photons from the same subject is more lens area.

Maybe you can filter a little better if you have more pixels. I'd imagine the
dynamic range sucks though if each pixel is so small that it saturates
quickly.

So, if you're shopping for a camera, what determines how your photos come out
in anything but the brightest sunlight is actually the lens. You should be
shopping primarily for a good (read large aperture) lens, with a decent camera
attached / bundled. Or if you want to go further, a system that is offering
good lenses.

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klodolph
> I'd imagine the dynamic range sucks though if each pixel is so small that it
> saturates quickly.

Well, if you replace a single sensor with four sensors that saturate more
easily, observe that the chance that all four sensors saturate may be less
than the chance that the original, larger sensor saturates. Answering the
question, "how much light actually fell on these four sensors" becomes a more
difficult problem and may yield greater error but is still tractable.

For you with a math background:

Let X_i be the amount of light that actually falls on sensor i, for i=1..4,
and let e_i be the amount of uncorrelated noise. The sensor readouts are Y_i,
where Y_i = min(X_i + e_i, sat) and sat is the saturation. Let X=sum(X_i). We
know that X and each X_i follow approximately a Poisson distribution and we
wish to know the parameter of the distribution for X.

Obviously, if Y_i = sat for all i then we are SOL. However, if not, then we
can always use some kind of reasonable estimator for the desired parameter.

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Gravityloss
Well, say you take a back-lighted image of a person against the sky.

Your camera software chooses the shutter speed, aperture and iso sensitivity
according to some formula like average lighting in the scene. But the real
world has such huge dynamics so that basically either the whole sky is washed
out or then you can't make out the person's face.

So basically _all_ the pixels where the sky light falls on, oversaturate. If
you lower the shutter speed, sensitivity and aperture so that the sky stays
just below saturation, then you conversely catch very very few photons from
the person. The person may appear pitch black or at best, really noisy, since
the photons are so few. With noise, you often actually get color noise since
because of the Bayer mask, the single photons hit random color pixels here and
there. It looks really bad and cheap. Actually, that's the tell tale sign of
low dynamic range and tiny pixels.

What do people do with even 12 megapixel 4000x3000 images? I'd settle with
2000x1500 - still greater than any resolution on any of the screens I own, and
the dynamic range could potentially be better. The full res images look really
bad and noisy anyway.

Actually, most of internet's picture content is just too large photos which
for the most part don't contain any useful information: below some resolution
you are just recording noise. I've set my compact to 5 megapixels.

Yet we haven't seen the end of wasted bit proportion. Phones recording full HD
video and later 4K and 8K will explode the data demands a thousand times.
Everybody will watch those resized to much smaller resolutions too.

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Juha
"The phone uses a technique that Nokia calls over-sampling, to produce crystal
clear, noiseless images with an effective resolution of 5 megapixels." At
first this sentence made me think it might be just a marketing trick, but
seeing the sensor size I see there might be something truly innovative here.

I first thought the sensor size must be a mistake, 1/1.2" huge, it is larger
than any point&shoot camera (biggest ones are 1/1.5" like Canon G1-X) and its
area is ~60% of normal DSLR sensor area. But still the 41MP sounds huge, it
remains to be seen how much that MP count affects the actual image resolution.
Maybe Nokia should just start making P&S cameras if it's really that good.

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nodata
It's that time again - anyone got good suggestions on how to represent photo
quality with a single number?

~~~
zokier
Resolving power. Take a photo of test pattern, and measure how many lines/mm
you can see.

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klodolph
Resolving power at various f-stops + noise at various gain settings (ISO
speeds) + available dynamic range + color gamut, although the color gamut
available is likely more than you need.

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krobertson
No picture of the phone? If they unveiled it, then you'd think there'd be a
picture of it.

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indy
The Verge has some photos of the phone:
[http://www.theverge.com/2012/2/27/2827158/nokia-808-pureview...](http://www.theverge.com/2012/2/27/2827158/nokia-808-pureview-
launch-pictures-video-preview)

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StavrosK
My phone can do infinite resolution, I just stick the image in the Gimp and
resize it to however large I want.

What the hell, sensationalist title?

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jhdevos
No, this phone will actually have a 41MP sensor. It will typically produce 5
or 8MP images, though, downsampling the original image, resulting in a lot
lower noise than with a normal 5 or 8MP camera-on-a-phone.

It really sounds pretty neat.

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StavrosK
Oh, sorry, I thought they were doing the opposite (upsampling to 41 MP from
5MP effective).

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klodolph
To be fair, that's what every webcam on the market does. (Logitech advertises
5 MP photos from a 1280x720 sensor on the C310. They're more than doubling the
resolution in software.)

