photon rate
DESCRIPTION
Reality Rate of incoming light is fluctuating. Ideal Rate of incoming light is constant. End of exposure. End of exposure. Photon rate. Photon rate. Time. Time. How much fluctuation?. √ n. Dictated by Poisson ( pwasõ ) Distribution For n total photons in exposure, - PowerPoint PPT PresentationTRANSCRIPT
Photonrate
Time
End of exposure End of exposure
IdealRate of incoming light is constant
RealityRate of incoming light is fluctuating
Photonrate
Time
How much fluctuation?
√nDictated by Poisson (pwasõ) Distribution
For n total photons in exposure,
standard deviation =
Photons collected = n + √n
If n = 10,000 photons,Photons collected = 10,000 + √10,000 = 10,000 + 100 photons
10,000 photon
s
9,900photon
s
10,100photon
s
9,950photon
s
√n, so what?Variable brightness = noise!
Noise monsterOne of the photographer’s worst enemies
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000%
2%
4%
6%
8%
10%
12%Proportion of fluctuation
sqrt(n)/n
Pro
porti
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Fluc
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(√(n
)/n)
Photons
0 500 1000 1500 2000 2500 3000 35000%
1%
2%
3%
4%
5%
6%
7%
8%
Canon A570ISCanon A570IS
ISO100
ISO200
ISO400
ISO800
ISO1600
Pro
porti
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f Pho
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Fluc
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(√(n
)/n)
Photons
Canon A570IS7.1 Megapixels1/2.5” sensor5.76 x 4.29mm (24.7mm2)Density: 3.48 μm2/pixel
0 500 1000 1500 2000 2500 3000 35000%
2%
4%
6%
8%
10%
12%
Canon 5DNikon D300Sony H9
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Fluc
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(√(n
)/n)
Photons
90 900 90000%
2%
4%
6%
8%
10%
12%
Canon 5DNikon D300Sony H9
Pro
porti
on o
f Pho
ton
Fluc
tuat
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(√(n
)/n)
Photons
ISO100 ISO200 ISO400
ISO800 ISO1600
Canon A570IS7.1 Megapixels1/2.5” sensor5.74 x 4.3mm (24.7mm2)Area: 3.48 μm2/pixel
0 500 1000 1500 2000 2500 3000 35000%1%2%3%4%5%6%7%8%
100200400
800
1600
images: dcresource.com
0 10002000300040005000600070008000-2%
0%
2%
4%
6%
8%
ISO100 ISO200 ISO400
ISO800 ISO1600
Fuji F306.1 Megapixels1/1.7” sensor7.7 x 5.77mm (44.4mm2)Area: 7.27 μm2/pixel
100200400800
1600
images: dcresource.com
0 100002000030000400005000060000-2%
0%
2%
4%
6%
8%
ISO100 ISO200 ISO400
ISO800 ISO1600
Canon 30D8.2 MegapixelsAPS-C sensor22.5 x 15mm (337.5mm2)Area: 41.16 μm2/pixel
1002004008001600
images: dcresource.com
30D
30D
F30
F30
A570IS
A570IS
8.2 Megapixels22.5 x 15mm (337.5mm2)Density: 41.16 μm2/pixel
6.1 Megapixels7.7 x 5.77mm (44.4mm2)Density: 7.27 μm2/pixel
7.1 Megapixels5.76 x 4.29mm (24.7mm2)Density: 3.48 μm2/pixel
ISO100 ISO200 ISO400 ISO800 ISO16000%
1%
2%
3%
4%
5%
6%
7%
8%Canon A570IS
Fuji F30
Canon 30D
Canon 5D
Pro
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(√(n
)/n)
ISO
More photowells mean less photons per pixel
Making matters worse, circuitry must occupy some space between each photowell – the more photowells, the more space circuitry takes up.
SummaryMore pixels, smaller sensor => less light per pixel => more noiseLess pixels, bigger sensor => more light per pixels => less noise
In theory, the biggest sensor with the least pixels will give us the best image, in terms of noise.
A 1-pixel sensor would be ideal.
With 1 pixel, we’d have low noise but no detail.
Many pixels => High detail, high noiseFew pixels => Low detail, low noise
The “Megapixel Myth”: Detail vs. Noise
Megapixels: Detail vs. Noise
Facebook profile picture: 4x6 studio print at 300dpi:
5x7 studio print at 300dpiStandard VGA TV:
1080p HDTV: Projector Screen:
8.5x11in, 300dpi magazine spread:10x14in, 150dpi full-page spread in Daily Cal:
Giant 20x30in poster print at 150dpi:
0.03 MP2.16 MP3.15 MP0.35 MP2.07 MP1.92 MP8.42 MP3.15 MP13.5 MP
How many pixels do we need?:
If you only look at pictures on the computer, 2-3MPIf you make non-poster-size prints (4x6, 5x7, 8x10), 3-4MP
More pixels beyond this don’t add detail, but contribute to greater noise
Caveat: assuming same sensor technology
Chrominance NoiseVariation in color
Luminance NoiseVariation in brightness
Random NoiseFluctuation in light input (random distribution of photons)
Fixed Pattern Noise-Consistently reproducible noise-Caused by electronics, sensor defects, heat-Manifested as “hot pixels” or luminance anomalies-Since noise is reproducible (non-random), easily fixed by dark frame subtraction