![Page 1: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/1.jpg)
When Does a Camera See Rain?
Kshitiz Garg, Shree K. Nayar
ICCV’ 05
![Page 2: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/2.jpg)
Outline
Abstract Dynamic Weather And Vision Visibility of Rain Camera Parameters for Rain Removal Camera Based Rain Gauge Conclusion
![Page 3: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/3.jpg)
Abstract
The Intensity fluctuations depend on the camera parameters, the properties of rain, and the brightness of the scene.
We use the camera parameters to remove rain in images and videos.
![Page 4: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/4.jpg)
Dynamic Weather And Vision
Dynamic weather (rain and snow) introduces sharp intensity fluctuation in images and videos.
![Page 5: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/5.jpg)
Dynamic Weather And Vision (Cont’d) Analysis of Visibility of Rain
The square of the raindrop size The brightness of the background scene Exposure time The depth of field
![Page 6: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/6.jpg)
Dynamic Weather And Vision (Cont’d) Camera Parameters for Removal of Rain
Exposure time F-number Focus setting
![Page 7: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/7.jpg)
Dynamic Weather And Vision (Cont’d) Camera Based Rain Gauge
Camera parameters can be set to enhance the visual effects of rain.
We can build a camera-based rain gauge to measure rain rate.
![Page 8: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/8.jpg)
Visibility of Rain
Variance at a pixel over time can be used to measure the visibility of rain and can be used as a quantitative measure of it.
![Page 9: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/9.jpg)
Visibility of Rain (Cont’d)
Camera and Intensity of a Raindrop
LkIN
Tkk
N
kTLTL
NkI
0
20
22
4
1
4
Ref:
B.K.P. Horn. Robot Vision. The MIT Press, 1986.
radiance the
time exposure the
number-F the
gain camera the
intensity the
L:
T:
N:
k:
I:
![Page 10: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/10.jpg)
Visibility of Rain (Cont’d)
Raindrops and Exposure Time
fazm 2
Rain visible region: mRzz 0
Rain visible region drop the ofradius the
pixels in length focal the
a:
f:
![Page 11: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/11.jpg)
Visibility of Rain (Cont’d)
Raindrops and Exposure Time When :
When :
mzz
mzz
T
LLT
kIII brbr
10
zT
LLTzv
fakI br
114 2
0
Ref: K. Garg and S.K. Nayar. Detection and removal of rain in videos. In CVPR04,2004.
view. of field the within
stays drop a that time the
intensity. background the
intensity. blurred-motion the
τ:
: I
: I
b
r
![Page 12: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/12.jpg)
Visibility of Rain (Cont’d)
Rain and Depth of Field
Since raindrops fall at high velocity, we assume
I
bTvb
TvI
A
AI
cic
idd
ci bTv
Ib
Ic
d
Ref: K. Garg and S.K. Nayar. Detection and removal of rain in videos. In CVPR04,2004.
kernel.defocus the of diameter the
drop. focused the of width the
streak. rain defocused the ofareas the
streak. rain focused the ofareas the
: b
ω:
: A
A:
c
d
![Page 13: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/13.jpg)
Visibility of Rain (Cont’d)
Rain and Depth of Field When :
When :
mzz
mzz
brc
d LLTb
I
brc
d LLTzv
fa
bI
1
1
1 2
Ref: K. Garg and S.K. Nayar. Detection and removal of rain in videos. In CVPR04,2004.
![Page 14: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/14.jpg)
Visibility of Rain (Cont’d)
Camera Parameters and Volume of Rain We partition the volume into thin layers of rain of
thickness .
The variance due to a variance of rain is then the sum of the variances due to the different layers.
z
![Page 15: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/15.jpg)
Visibility of Rain (Cont’d)
Camera Parameters and Volume of Rain The variance due to a single layer of rain:
zIzznzI dd
r22 ,
z. depth at raindrop a to due streak defocused the of width the
view of fields pixel' a throughpass that layer the indrops of number mean the
(z): ω
.(z): nd
zbzz
fdz
vT
LLakdzzI
c
brr
2420
2 4,
,1)max(
density. size drop the
drop. the of size the
a
fzω(z):
ρ:
a:
![Page 16: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/16.jpg)
Visibility of Rain (Cont’d)
Camera Parameters and Volume of Rain The standard deviation due to a volume of rain:
02
0 f,N,zGLLav
ρa
T
kIσ brr
.): G(f,N,z
(z)bω(z)z
fdz)G(f,N,z
c
planefocus the ofz0 distance the and N, number-F length, focal of function a0
0
![Page 17: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/17.jpg)
Visibility of Rain (Cont’d)
Camera Parameters and Volume of Rain The visibility of rain decreases as with
exposure time of the camera.T
1
![Page 18: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/18.jpg)
Visibility of Rain (Cont’d)
Camera Parameters and Volume of Rain initially increases rapidly with F-number and
then reaches saturation for higher F-number. r N
![Page 19: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/19.jpg)
Visibility of Rain (Cont’d)
Camera Parameters and Volume of Rain dependence with respect to distance of the f
ocal plane.r 0z
![Page 20: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/20.jpg)
Camera Parameters for Rain Removal Reducing Rain using Depth of Field
As decreases, decreases.N I
![Page 21: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/21.jpg)
Camera Parameters for Rain Removal (Cont’d) Reducing Rain using Exposure Time
As increases, decreases. IT
![Page 22: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/22.jpg)
Camera Parameters for Rain Removal (Cont’d) Reducing Rain using Multiple Parameters
![Page 23: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/23.jpg)
Camera Parameters for Rain Removal (Cont’d) Reducing Heavy Rain
![Page 24: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/24.jpg)
Camera Parameters for Rain Removal (Cont’d) This method will not be able to reduce rain in
scenes with very fast motion and when objects are very close to the camera.
![Page 25: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/25.jpg)
Camera Based Rain Gauge
A camera-based rain gauge - a device that measures rain rate.
daavaadaahh
aav
36
3
410*6.3
200
Ref: R. Gunn and G.D. Kinzer. Terminal velocity for water droplet in stagnant air. J. Metero., 6:243–248, 1949.T. Wang and R.S Clifford. Use of rainfall-induced optical scintillations to measure path-averaged rain parameters. JOSA, 8:927–937, 1975.
rain. of density the
rain. ofradius the
:)(
:
a
a
![Page 26: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/26.jpg)
Camera Based Rain Gauge (Cont’d)
![Page 27: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/27.jpg)
Conclusion
The visibility of rain is affected by factors such as camera parameters, properties of rain, and the brightness of scene.
This method is not as effective in reducing rain from scenes with very heavy rain or scenes with fast-moving objects that are close to the camera.
![Page 28: When Does a Camera See Rain? Kshitiz Garg, Shree K. Nayar ICCV’ 05](https://reader038.vdocument.in/reader038/viewer/2022103023/56649e5c5503460f94b54bee/html5/thumbnails/28.jpg)
Conclusion (Cont’d)
The visibility of rain can be enhanced to build an inexpensive and portable camera-based rain gauge that provides instantaneous rain rate.