Dark Flash Photography - PowerPoint PPT Presentation

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Dark Flash Photography

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First, we ll start with the eye. * We will look at the spectral sensitivities of 2 types of sensor: the human eye and DSLR camera. First, we ll start with the eye. – PowerPoint PPT presentation

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Learn more at: https://cs.nyu.edu
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Tags: dark | dslr | flash | photography

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Title: Dark Flash Photography


1
Dark Flash Photography
  • Dilip Krishnan
  • Rob Fergus
  • Dept. of Computer ScienceCourant Institute, New
    York University

2
(No Transcript)
3
Taking Photos in Low Light Levels
Taking Photos in Low Light Levels
4
Taking Photos in Low Light Levels
  • Want to avoid sensor noise camera shake
    Possible solutions

Drawbacks
Can be used in conjunctionwith our approach
Our paper addresses these issues
5
Dark Flash Photography
  • Dark flash is 200 times dimmer than conventional

Ground truth
Reconstruction
2. Ambient image
1. Dark Flash image
6
Key Challenges
  1. How to add light to the scene without it being
    perceived by people.
  2. How to obtain an image to true colors.

7
Two Sensors
The Human Retina
Digital Camera Sensor
8
Human Retina Spectral Sensitivity
9
Human Retina Sensitivity Log Scale
NoteSteep fall off outside400-700nmrange
10
Two Sensors
The Human Retina
Digital Camera Sensor
11
Camera Spectral Sensitivity
  • Spectral response curves for an unmodified DSLR

12
Camera Spectral Sensitivity
Modify camera by 1. Remove IR-blocksensor
filter 2. Adding lens filter to remove IR
gt800nm ? Some sensitivityin UV IR just
outside visible
13
Camera Spectral Sensitivity
  • Comparison with human sensitivity curve
  • Cameras response is significantly broader
  • Possible to addlight without being easy
    perceived

Human Response Curve (not to scale)
14
Dark Flash Emission Spectrum
  • CameraSpectralSensitivity
  • Dark FlashEmission

15
Demonstration of Dark Flash
  • Please look directly at the demonstration,NOT at
    the projection screens

16
Comparison to Visible Flash
  • Both flashes will fire simultaneously
  • Both give comparable camera exposure
  • Dark flash is 220x dimmer than visible flash

17
Flash Safety
  • Eye is most sensitive part of the body to UV
  • Government TLVtables specify Hazard Factor
    safe limits
  • ? Safety limit is 115,000 Flashesper day _at_ 1m
  • Equivalent to being outside for 1/100th second

Dark Flash
Hazard Factor
Dark Light _at_ 1m for 1 sec
18
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19
Human Spectral Sensitivity Function
Shuman(?)
Vos 1978
20
Log Human Spectral Sensitivity Function
log Shuman(?)
Vos 1978
21
Camera Spectral Sensitivity
  • Spectral response curves for DSLR with
    IR-blocksensor filter removed
  • Too much IRsensitivity forour application?
    add partialIR block filterto lens

22
Camera Spectral Sensitivity
  • Spectral response curves for DSLR with
    IR-blocksensor filter removed IR lens filter
  • Some sensitivityin UV IRjust outsidevisible

23
(No Transcript)
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