Title: Dark Flash Photography
1Dark Flash Photography
- Dilip Krishnan
- Rob Fergus
- Dept. of Computer ScienceCourant Institute, New
York University
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3Taking Photos in Low Light Levels
Taking Photos in Low Light Levels
4Taking 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
5Dark Flash Photography
- Dark flash is 200 times dimmer than conventional
Ground truth
Reconstruction
2. Ambient image
1. Dark Flash image
6Key Challenges
- How to add light to the scene without it being
perceived by people. - How to obtain an image to true colors.
7Two Sensors
The Human Retina
Digital Camera Sensor
8Human Retina Spectral Sensitivity
9Human Retina Sensitivity Log Scale
NoteSteep fall off outside400-700nmrange
10Two Sensors
The Human Retina
Digital Camera Sensor
11Camera Spectral Sensitivity
- Spectral response curves for an unmodified DSLR
12Camera 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
13Camera 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)
14Dark Flash Emission Spectrum
- CameraSpectralSensitivity
- Dark FlashEmission
15Demonstration of Dark Flash
- Please look directly at the demonstration,NOT at
the projection screens
16Comparison to Visible Flash
- Both flashes will fire simultaneously
- Both give comparable camera exposure
- Dark flash is 220x dimmer than visible flash
17Flash 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
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19Human Spectral Sensitivity Function
Shuman(?)
Vos 1978
20Log Human Spectral Sensitivity Function
log Shuman(?)
Vos 1978
21Camera Spectral Sensitivity
- Spectral response curves for DSLR with
IR-blocksensor filter removed - Too much IRsensitivity forour application?
add partialIR block filterto lens
22Camera Spectral Sensitivity
- Spectral response curves for DSLR with
IR-blocksensor filter removed IR lens filter - Some sensitivityin UV IRjust outsidevisible
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