Digital camera - part 3

Lens and Focal length

Most important diff b/n digicam and a 35mm camera is the focal length which is the distance b/n the lens and the surface of the sensor.The surface of a film sensor is larger than a CCD sensor. These are the four different types of lenses on the digicam:

• fixed-focus, fixed-zoom lenses: found on disposable and inexpensive film camera
• optical zoom lenses with autofocus: you'll have 'wide', 'telephoto' options and automatic focus (similar to lens on video camcorder).
• Digital-zoom lenses: camera takes pixels from center of image and "interpolates" them to make a full-size image.May produce grainy pictures- same effect if u use software to edit
• Replaceable lens system: High-end digicam can use this system and can even use lenses from 35mm cameras in some cases.

Some important information here:

Focal length 35mm film cam equivalent view typical uses
5.4mm 35mm Things look smaller wide-angle shots, lands
farther away apes, large buildings
grps of ppl
7.7mm 50mm abt same as wat eye "normal" shots of ppl
sees and objects
16.2mm 105mm things are magnified Telephoto shots, close
and appear closer ups
i try editing table but looks like the whole table shifts down a lot sorry for the inconvenience caused just read chronologically... should be able to get it.

Optical zoom vs Digital zoom

An optical zoom actually changes the focal length of the lensand thus image is magnified by the lens sometimes called optics, hence the name optical zoom.Light is spread across the entire CCD sensorand all pixels can be used.

Digital zoom magnifies a portion of image that hits sensor. If ur shooting image with 2x digital zoom, camera will use half of the pixels at the center of CCD, ignore other pixels and use interpolation techniques to add detail to photo.Basically same as magnifying on computer software...

Summary

You aim at subject with camera and adjust optical zoom to get closer of further away. You press the shutter release lightly. The camera automatically focuses on subject and take a reading of the avail light. It sets the aperture and shutter speed for optimal exposure. You press the shutter release all the way and CCD is reset and then exposed to light building up electrical charge until shutter closes. The ADC measures the charge and creates digital signal that represent the calues of the charges at each pixel. A processor interpolates the data from diff pixels to create natural colour. The processor may perform a preset lvl of compression on the data. The info is then stored in some memory device like flashcard.

What i Think
If ur looking for quality then look out for optical zoom and digicam with CCD sensor. Digital zoom is not that important if ur looking at magnifying images, this can easily be done with computer software. Of course, if ur looking at cheap cameras and just want to have fun with photos but don't really matter abt quality go for cameras with CMOS... If u only want images to post on website or email to frens 640x 480 resolution is enough (307200 pixels)To enlarge photo prints 2 or 3 megapixels but i guess most cameras are ard there...

Digital camera - part 2

Digitizing information
Light is converted to electrical charge. However, electrical charges are not in digital signal. Thus, the signal must be passed through analog-to-digital converter(ADC). Photons of light hit the photosites, thus accumulating electrical charges. Then the ADC measures the amt which is considered analog info. It then converts to the binary info.

Photosites and Pixels
"A camera claims to be a 2.1-megapixel camera and it is capable of producing images with a resolution of 1600x1200. Let's do the math: a 1600x1200 image contains 1,920,000 pixels."
Well, this is the camera indeed has 2.1 million photosites on the CCD, just that some of the photosites aren't used for imaging. Since CCD is an analog device, some sort of circuitry(dyed black so doesn't absorb light) is needed to connect to the ADC so that it can measure the amt of charges.

These are egs of storage systems used in digital cameras:

• Built-in memory- built-in flash memory
• SmartMedia card
• CompactFlash
• Memory Stick
• Floppy disk
• Hard disk
• Writeable CD and DVD

The two main file formats used by digital cameras are TIFF and JPEG. TIFF is an uncompressed format and JPEG is a compressed format. Most cameras use the JPEG file format for storing pictures, and they sometimes offer quality settings (such as medium or high).

Compression

Some of the patterns repeat over again in a picture, like the blue sky... thus digicam makes use of repeated pattern to create exactly the same effect and this is known as repetition.

Some compression throw away certain meaningless data. Thus lower the resolution, more data is thrown out. This is known as irrelevancy.

Controlling Light

The word camera comes from the term camera obscura. Camera meaning room or chamber and obscura meaning dark. Thus camera means dark room. It is crucial to control the amt of light entering because if too much light enters, some info would be lostbecasue the sensor cannot hold any more of the light.

Aperture is the small opening found in the camera and is located at the back of the lens. On a very bright day, the light reflected off your image may be very intense, thus a small aperture is needed. Likewise, if it is a cloudy day, aperture should be enlarged to produce a brighter image. Interestingly, this works out to be the same as the pupil of our eye. Our pupil tends to dilate when we are in a dark room and shrink when we are under the sun.

Shutter speed

Basically, it means the amt of time light is allowed to enter the aperture. Film-based camera has mechanical shutter. So if u expose ur film, it can't be wiped clean again. However, the sensor in a digital camera can be easily resetted every time and it is called digital shutter.