seminar.pptx
- 1. Rough History of Photography Digital Sensors and Lenses Zoom, Stabilization, Compression Smartphone Camera Technology Pelican Imaging's 16-lens camera module is designed for next-gen mobile devices coming in 2014.
- 2. Rough History of Photography ? Mid 1800s Silver nitrate glass plates ? Early 1900s B&W silent “movies” Colour “talkies” ? Mid 1900s B&W TVs ? Late 1900s LCD TV’s Digital photography Cellular phones Internet ? Early 2000s Digital movie making Smartphone cameras
- 3. About Photographic Film ? ? Plastic coated with photosensitive emulsion. When light strikes the chemical it causes a reaction. Different formulas have different sensitivities to light. Film has a resolution of ~20 Megapixels. Film speed is a measure of how much light is required to cause the photochemical reaction. Slower, less reactive, film has finer grain (resolution) and better color fidelity. The camera shutter speed and aperture needs to be set within narrow range for successful photography.
- 4. Digital Sensors ? ? ? ? Electronics control exposure time (shutter sound is artificial) Photons (light) energize electrons in CMOS (Complementary Metal Oxide Semiconductor) which can be collected by picture elements (pixels). There are colour filters on each pixel to allow only Red, Blue, or Green (RGB) light to pass to the semiconductor element. Smaller sensor chips have physically smaller pixels = more light is required to form an image.
- 5. CMOS Sensor Chip Sony Image Sensor
- 6. Apertures and Pixels Small aperture/lens = limited light, large depth of field Large aperture/lens = large amount light, small depth of field Small Sensor (slow film) needs more light Many pixels on small sensor = light spillage
- 7. Basic Optics Object, aperture, Lens, shutter, sensor/film Small aperture gives greater depth of field
- 8. Format Sensor size Pixel Pitch Camera 1/2.5” 5.76x4.29mm <1 micron Camera Phone 1/1.7” 7.6x5.7mm 1.7 microns Compact camera 5.7 microns Consumer DSLR APS-C22.2x14.8- 23.6x15.7mm Full Frame 36x24mm 8.4 microns Pro DSLR Basic Optics
- 9. Lenses
- 10. Lenses Five element “Optical glass” lenses (with scratch resistant sapphire lens cover) Limited (no) anti-reflective coatings Purple haze on iPhone Digital (not optical) zoom
- 11. Noise Sensors are made up of many tiny receptors, pixels, which record light. ?Large pixels are more sensitive to light. – Camera makers boost the gain in small sensors to capture a usable image. ?On large sensors, each pixel is walled off to prevent light from spilling over to adjacent pixels. – Small chips with high megapixel counts have light spillage (flares). – Transistors under each CMOS pixel generate noise.
- 12. Digital Zoom ? Smartphone cameras do not have optical zoom - digital zoom crops a region and expands the pixel size. No increase in resolution or number of pixels.
- 13. Compression ? Image is compressed to reduce storage requirements. ? 8x8 blocks are averaged ? Static areas (from frame to frame) copied. – Moving objects produce ghosts and blurring – Samsung allows editing of unwanted moving objects ? Dedicated microprocessors in cameras can compress on-the-fly
- 14. Infrared Sensitivity ? Camera sensors “see” a broader spectrum of light than the human eye. (Shine a TV remote control into your camera). The sensitivity to infrared may cause some color distortion.
- 15. Image Stabilization ? Larger cameras may have “optical” stabilization where the sensor is mechanically moved to compensate for camera shake. Smaller cameras typically do not have mechanical stabilization and use “digital” stabilization that takes multiple shots and averages the pixels. ? Digital stabilization does NOT work for video
- 16. Thank You .