Post on 20-Jan-2016
Digital CameraTAVITA 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
http://www.1derful.info/Words/DSLRoptics.gif
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
http://static.canalblog.com/storagev1/volker.canalblog.com/images/E_330_LiveView_A_mode_1.JPG
Image Sensor - CMOS◦ Advantages
◦ Require less power than CCD◦ Cheaper to manufacture
◦ Disadvantages◦ More susceptible to noise◦ Less sensitive to light than CCD
http://pentaxph.com/wp-content/uploads/2013/08/CMOS-Image-Sensor.jpg
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
https://upload.wikimedia.org/wikipedia/commons/1/1c/Bayer_pattern_on_sensor_profile.svg
https://upload.wikimedia.org/wikipedia/commons/3/37/Bayer_pattern_on_sensor.svg
Bayer Filter
https://upload.wikimedia.org/wikipedia/commons/f/f2/Colorful_spring_garden_Bayer.png
Aperture◦ hole or an opening through which light
travels◦ Aperture size is referred to in f-stops◦ It controls the depth of field
http://pixelarge.com/wp-content/uploads/2014/09/lens-aperture-f-stop.jpg
Aperture
http://www.teabreaktog.com/photography-for-beginners/all-about-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
http://4.bp.blogspot.com/-3vGCiFeJ80w/Va0t6I0okwI/AAAAAAAAC64/iVJ-leh6Vzo/s1600/8.png
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
http://slrreviewguide.biz/canon-eos-1200d-with-18-55mm-55-250mm-lens/
ISO
Low light environment with high ISO (1600)http://www.slrphotographyguide.com/images/high-iso.jpg
Potential Exam Questions1. 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?
References◦ http://www.teabreaktog.com/photography-for-beginners/all-about-aperture/◦ http://www.slrphotographyguide.com/camera/settings/iso.shtml◦ https://www.teledynedalsa.com/imaging/knowledge-center/appnotes/ccd-vs-cmos/◦ http://electronics.howstuffworks.com/cameras-photography/digital/question362.htm◦ https://en.wikipedia.org/wiki/Image_sensor◦ https://en.wikipedia.org/wiki/Shutter_speed◦ https://photographylife.com/what-is-shutter-speed-in-photography◦ https://en.wikipedia.org/wiki/Digital_camera◦ http://petapixel.com/2015/05/26/film-vs-digital-a-comparison-of-the-advantages-and-disadvantages/◦ https://www.youtube.com/watch?v=F8T94sdiNjc