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Commit e05a05b6 authored by Quentin Bolsee's avatar Quentin Bolsee
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title: Note
color: purple
url: https://quentinbolsee.pages.cba.mit.edu
baseurl: mas865.24_computer-vision
# url: https://quentinbolsee.pages.cba.mit.edu
# baseurl: mas865.24_computer-vision
topics/01_cameras/img/aperture.png

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topics/01_cameras/img/bayer.png

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topics/01_cameras/img/lens_distortion.png

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topics/01_cameras/img/shutter.gif

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......@@ -127,11 +127,27 @@ The image plane is an imaginary construct sitting in front of the sensor, at one
It is common to choose the $z$ axis to point **toward** the scene, and the $y$ axis to point downward. This matches the conventional downward-pointing vertical coordinates in pixel coordinates, with $(u,v)=(0,0)$ in the top-left corner.
## CCD
## Technologies
## CMOS
We'll focus on the two main families of digital sensors: CCD and CMOS.
## Bayer pattern
In both families, the actual light sensing is based on the electron-hole pair generation in MOS devices.
### CCD
In CCD sensors, the generated charges in the photodiodes are accumulated under a potential well, controlled by a voltage on the gate.
Charges can be moved to a neighboring pixel by performing a specific sequence on the gates. By shifting the charges all the way to the edge of the sensor, individual pixel values can be readout sequentially.
Advantage of CCD sensors include the simplicity of their design, and the large surface dedicated to sensing light. One disadvantage is the readout speed bottleneck caused by using a single decoding unit.
### CMOS
## Bayer filter
![](img/bayer.png)
<!-- source:https://en.wikipedia.org/wiki/Bayer_filter -->
# Lens
......@@ -139,14 +155,30 @@ It is common to choose the $z$ axis to point **toward** the scene, and the $y$ a
## Distortion
![](img/lens_distortion.png)
# Aperture
![](img/aperture.png)
<!-- source:https://www.adorama.com/alc/camera-basics-aperture/ -->
# Shutter
## Mechanical shutter
![](img/shutter.gif)
<!-- source:https://www.youtube.com/watch?v=CmjeCchGRQo -->
## Electronic shutter
# Photography basics
## The 3 parameters: shutter speed, aperture, ISO
## The 3 parameters
- Aperture
- Shutter speed
- ISO
Each parameter can be converted to a $\log_2$ scale. A common name for a unit on that scale is a **stop**. For example, increasing exposure by one stop can be achieved by doubling the shutter speed, doubling the ISO or increasing the aperture by $\sqrt{2}$.
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