Tutorials:

	Tutorials
	The difference between CMOS and CCD sensors: CMOS short for complementary metal oxide semiconductor and CCD short for charge-coupled device are image sensor chips that capture the image in digital cameras. CMOS semiconductors use both NMOS (negative polarity) and PMOS (positive polarity) circuits. Since only one of the circuit types is on at any given time, CMOS chips require less power than chips using just one type of transistor. This makes them particularly attractive for use in battery-powered devices, such as camera phones. The CCD chip is an instrument whose semiconductors are connected so that the output of one serves as the input of the next. The differences between the chips are the chip sensitivity and cost. CCD chips are more sensitive therefore the image quality is cleaner were the CMOS chip gets a hard time handling noise and produces small defects in the image. However we find that CMOS chips are more common in camera phones because they are less expensive to manufacture and operate at lower voltages, which means that less power is required. Another advantage for CMOS is that it can capture highlights such as the sparkle of jewelry or the glint of sunlight reflecting across a lake without creating halos around very bright objects. CCD Sensor CMOS Sensor Optical vs. digital zoom There are two ways to magnify an image: one way is by using a digital zoom which enlarge the image pixels by using the camera's hardware or software. The second way is by using an optical zoom that changes the physical length of the lens to draw the image closer. When we use a Digital zoom a portion is being cropped and then enlarged to the requested size. This can cause loss of information (pixelization). In an optical zoom the lens collects lights rays and projects them onto the sensor. By adjusting the glass elements inside the lens the projected image appears to be larger. Only after all these adjustments the image is being recorded as pixels. Unlike digital zoom this ensures a better image quality and does not lose information. Although every decent digital camera has an optical zoom, in camera phones we usually find only digital zoom due to the size factor. The few camera phones that do have an optical zoom option are much bigger and heavier. So until a smaller and lighter cheap lens will be invented we will have to relay on digital zoom because size does matter. Camera resolution - from pixels to mega pixels Pixel = the pixel is the smallest part of a digitized or Digital Image with a given color and brightness value. The complete image is a rectangular array of pixels, the more pixels the higher the resolution of the picture. The camera resolution helps us define the camera quality by the number of vertical and horizontal pixels. It has a direct effect on the quality of the photos the camera is able to output. Pictures with a higher resolution can be enlarged a lot without causing a blur and. The resolution range starts from 0.1 megapixels to above 10 megapixels. The common range in camera phones is between 0.3-3 megapixels. Obviously sky is the limit and today we can find a 10 MP camera phone that just entered the market. The megapixel battle is going to continue forever it seems. In order to understand camera phones resolution we need to learn a few common terms: Sub QCIF - a resolution of 128 x 96 pixels or 0.01 MP. QCIF - is a quarter of CIF. A resolution of 176 X 144 pixels or 0.02 MP. CIF - Common Intermediate Format. A resolution of 352 X 288 pixels or 0.1 MP. QVGA - is a quarter of VGA. A resolution of 320 x 240 pixels or 0.07MP. VGA - Video Graphics Array. A resolution of 640 x 480 pixels or 0.3MP. SVGA - Super VGA. A resolution of 800 x 600 pixels or 0.5MP. SXGA - Super Extended Graphics Array. A resolution of 1280 x 1024pixels or 1.3MP. Auto focus - how does it work? Auto-focus = Describes a lens which automatically focuses the image on the subject in front of the lens. It brings maximum clarity or distinctness of an image rendered by an optical system. Focus is established when the lens move in and out until the sharpest possible image is projected onto the sensor. There are two types of auto focus: active and passive focus. Active auto focus uses an infrared signal to estimate the distance between the object and the camera. It is called active because the infrared light is always measuring the distance. Passive auto focus estimate the distance by computer analysis. The camera moves the lens in and out until it reaches the optimal image. Out-of-Focus In-Focus