Digital Camera TAVITA SU’A

Overview ◦Digital Camera ◦Image Sensor ◦CMOS ◦CCD ◦Color ◦Aperture ◦Shutter Speed ◦ISO

Digital Camera Allows images to be captured and stored in a digital format

Image Sensor ◦A device that converts an optical image (incoming light) into an electronic signal. ◦Small silicon chip that contain photosensitive diodes called photosites ◦2 Types ◦CCD (Charge Coupled Device) ◦CMOS (Complimentary Metal Oxide Semiconductor) ◦Both perform similarly in absorbing light photons

Image Sensor - CCD ◦Advantages ◦More sensitive to light ◦Produces better images in low light ◦Produces images with less noise ◦Disadvantages ◦Requires more battery than CMOS ◦More expensive than CMOS ◦ May suffer vertical smearing on bright light sources

Image Sensor - CMOS ◦Advantages ◦Require less power than CCD ◦Cheaper to manufacture ◦Disadvantages ◦More susceptible to noise ◦Less sensitive to light than CCD

Color ◦Each photosite is colorblind ◦Most sensors use a filter to get a full color image ◦Light must be separated and recorded in its primary colors ◦Color is usually recorded using: ◦Beam Splitter ◦Spinning Disk ◦Bayer Filter

Bayer Filter ◦Pattern of alternating color filters ◦Blue and green, then green and red ◦50% green, 25% blue, 25% red ◦Only requires 1 sensor _pattern_on_sensor_profile.svg _pattern_on_sensor.svg

Bayer Filter

Aperture ◦hole or an opening through which light travels ◦Aperture size is referred to in f-stops ◦ It controls the depth of field aperture-f-stop.jpg

Aperture ◦The depth of field is the distance of sharp focus in an image ◦The wider the aperture, the shallower the depth of filed ◦The narrower the aperture, the deeper the depth of field

Shutter Speed ◦ length of time the digital sensor is exposed to light ◦A typical shutter speed for photographs taken in sunlight is 1/125th of a second. ◦Very short shutter speeds can be used to freeze fast-moving subjects ◦Long shutter speeds can be used to blur a moving object

Shutter Speed

ISO ◦ level of sensitivity of the camera to available light ◦the lower the ISO number, the less sensitive to light and vice-versa ◦Increasing sensitivity adds grain or noise to pictures ◦Best to use lower ISO when there is ample light ◦increase the ISO when there is not enough light for the camera to be able to quickly capture an image

ISO

ISO Low light environment with high ISO (1600)

Potential Exam Questions 1.Discuss the advantages and disadvantages of CMOS and CCD image sensors. 2.Explain how a bayer filter is used to filter light. 3.What is the function of the aperture? How can it be used to modify images? 4.Which camera function(s) should be adjusted to freeze an object moving at high speeds? 5.What are the effects of increasing camera ISO? 6.If the amount of light in an object scene is raised, how should the camera be adjusted to compensate for it?

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