It seems as though the whole world is going digital. In music world Black Vinyl LP was first replaced by cassettes and then CD/DVD has completely replaced them. Digital TV is already in market and several channels are already broadcasting in digital format. And now you see that photography has also become. Digital. It is clear that future technology is digital so if you do not want to be left behind you will have to convert from conventional to digital. According to PSA journal today 60% prize winning photographs in annual competition are digital, which shows how quickly digital photography is replacing the conventional photography.
Photography is now so simple and immediately gratifying that is has become the most popular means of self expression. With digital camera you can now immediately see your results on LCD screens. More and more people are using camera in place of their notebooks.
Unlike any other creative medium photography relies more on technology and the technology of future is digital so in future you will be seeing the advancement in camera in digital line. Digital photography has also closed the darkroom and opened up an entirely new way to edit and present images. These advance digital camera are so easy to use but their technology is so advance and complex. In Digital photography we can see new developments daily. Familiarity and proficiency with camera technology are essential so that you can avoid getting trapped into using technology for its own sake.
What’s the most obvious difference between a digital and a conventional camera? That’s easy: no film. Instead of film, digital cameras use tiny memory cards to store images. A picture taken on film is composed of numerous, tiny, light-sensitive silver-halide crystals that are chemically-processed in order for the image to be made, whereas a picture recorded digitally is made up of numerous, tiny, light-sensitive pixels (Picture Elements) that form an image that can be viewed on a computer monitor or the viewing screen of some digital cameras.
The ability to edit images without the need for a darkroom or without having to send them to a professional lab is also a big attraction. Almost anyone with the right combination of hardware and software can scan images, then crop them for better composition, lighten or darken them, adjust the colors and even alter them so drastically that often they bore minimal resemblance to the original image. Not only could images be improved, but it is fun too. Text could be added to images, either inside the image itself or as captions placed beneath or beside them. And improvements in color printers and papers made printing pictures relatively simple and cheap.
How digital camera works:
The differences between digital and traditional photography happen to be after the light enters the camera. A traditional camera captures the images on film, while a digital camera captures the image on an image sensor. Image sensors are electronic devices made up of an array of electrodes (or photosites) which calculate light intensity. The most universally recognized type of image sensor for digital cameras is the CCD (Charge-Coupled Device) although others such as CMOS and Foveon are sometimes used. The number of photosites in the image sensor gives the digital camera its megapixel (millions of pixels) rating. Each photosite corresponds to a pixel in the final image, so a camera which is rated at six megapixels, for example, has an image sensor which is 3008 pixels wide by 2000 pixels high.
When light hits the image sensor it is converted into electrical signals which are built-up and fed to an analog-to-digital (A/D) converter. The A/D converter changes the electrical signal into binary numbers which are processed by a computer housed in the camera body. Once the numbers have been harvested the resulting image is stored on a memory card.
How the Camera Captures Color
Photosites can only measure intensity of light—not color. In order to produce a colour image, each photosite must be covered with a colored filter which can be red, blue, or green. These are the three primary colors which can be combined to produce any other colour including white.The colored filters are arranged in a grid so that there are twice as many green filters as there are red or blue. This is because the human eye is twice as sensitive to green light. Filters are arranged in a pattern called the Bayer pattern - one row of red, green, red, green (etc.), and the next row of blue, green, blue, green (etc).Since each photosite can only be covered with one coloured filter, computer processing is necessary to produce a full colored image. This is done by analyzing a certain pixel and its immediate neighbors and producing a composite colour from these calculations. For example, if a bright red pixel is surrounded by bright green and bright blue pixels, the bright red pixel must undeniably be white, because white is the combination of red, blue, and green. This process is called-demosaicing.After demosaicing the image is adjusted according to the settings on your camera. Most cameras have settings for brightness, contrast, and colour saturation. After these adjustments are made some cameras may also apply a sharpening algorithm to make the image clearer.The final step before saving the image on the memory card is to compress it. Most cameras use JPEG as a compression format. This reduces the size of the file by eliminating excess data. This information cannot be recovered, so JPEG is called a ‘lossy’ format.Several cameras have the ability to save uncompressed images as TIFF files or raw data. Raw data is the original photosite data even before demosaicing. It can be transferred to a computer for processing with special software that will perform all of the processing functions of the camera but with much greater control.
Important issues to consider:
For starters, it’s important to understand some of the technical issues associated with digital cameras.
Zooming Digitally & Optically
Digital camera makers have bandied about zoom lenses in an effort to wow customers but you have to pay attention to digital versus optical zoom. They are not interchangeable terms.
A zoom lens is any lens with an adjustable focal length, it doesn’t refer to close-ups, though zoom lenses are used to achieve them. An optical zoom will actually physically change the focal length of your lens, so the image is magnified by the lens itself. The lens is sometimes referred to as a camera’s optics and hence the term “optical zoom.”
A digital zoom, however, is a computer technique that magnifies a portion of the information that hits the CCD. If you are using a camera with a 2X digital zoom the camera will use half of the pixels at the center of the CCD and ignore the surrounding pixels. It then uses interpolation (educating guessing about the color) to provide detail. It gives you the appearance that you’re shooting with twice the magnification when actually you could achieve the same results by shooting the photo without a digital zoom and enlarging the picture at home with some image editing software.
Aspect Ratio
The aspect ratio of a camera is the ratio of the length of the sides of the images. For example, a traditional 35mm film frame is approximately 36mm wide and 24mm HIGH. This has an aspect ratio of 36:24, which can equally well be expressed as 3:2. Some digicams use the same aspect ratio for their digital images. For example most digital SLR (single lens reflex) cameras have a 3:2 aspect ratio. However, video monitors typically use a 4:3 aspect ratio. For example a monitor with a 800x600 display has a 4:3 aspect ratio. With this in mind, most consumer level digicams use a 4:3 aspect ratio for their images.
Sensor Size
The size of the digital sensor element (which is equivalent to the size of the negative for film cameras) is pretty small in all consumer digicams - typically around the size of a fingernail (and a small fingernail at that!). A 35mm film frame is 24mm high by 36mm wide but most digital cameras use sensors very much smaller than this. Nobody is quite sure why it’s being used for modern digital sensors since the “sizes” don’t really relate in any consistent way to the actual physical size of the sensor. However these names are widely used, so it’s best to know what they are. They are often listed in digital camera spec sheets. Most of the current small 5MP digital cameras use 1/1.8” sensors which are about 7mm x 5mm. They have an area 25x smaller than 35mm film and about 9.5x smaller than a small sensor digital SLR like the Canon EOS 10D. You might wonder why sensor size matters and that’s a pretty complex issue. The bottom line is that, for a given pixel count, the larger the sensor (and hence the larger the area of the individual pixels) the better the image quality and the lower the noise level. While large sensor cameras like the EOS 10D can operate at the equivalent of ISO 3200 (though the image does get noisy), many consumer digicams with small sensors cannot operate above ISO 400 before the noise becomes excessive.
Small sensors mean that short focal length lenses are needed to give the same field of view as cameras using larger sensors or 35mm film. So, for example, a typical consumer digicam may need a 7mm lens to give the same view as you would get using a 35mm focal length lens on a 35mm camera. This has consequences on depth of field and means that most consumer digicams have a vary large depth of field. Great if you want everything in focus, not so great if you want a blurred background.
White Balance
With film you can buy “daylight balanced film” for shooting outdoors or “tungsten balanced film” for shooting indoors under normal domestic lighting (not fluorescents!). If you use daylight film under tungsten light the images will be very yellow. If you use tungsten film in daylight the images will be very blue. With film you have to correct for the “color temperature” of the light using filters or by the right choice of film.
With digital you can pick your white balance to suit your light source, so that white looks white, not yellow or blue. Normally there is an automatic setting and the camera decides what white balance setting to use. However if you know what your light source is you can usually set the camera to it and this may give better results. Most digital cameras have settings for sunlight, shade, electronic flash, fluorescent lighting and tungsten lighting. Some have a manual or custom setting where you point the camera at a white card and let the camera figure out what setting to use to make it white.
Sensitivity
Sensitivity settings on digital cameras are the equivalent of ISO ratings on film. Just about every digital camera will have settings with a sensitivity equivalent to ISO 100 film and ISO 200 film. Many will have an ISO 400 setting, but above that the images from cameras with small sensors gets pretty noisy. The more expensive digital SLRs with much larger sensors have much higher sensitivity settings. At ISO 400 they are virtually noise free and some can go as high as ISO 3200 or even ISO 6400! Very few cameras have ISO setting lower than ISO 100 because noise levels are so low at ISO 100 there would be no real advantage in a slower setting. Quite a few digital cameras have an “auto” ISO setting, where the camera will pick from ISO 100, ISO 200 and sometimes ISO 400, depending on the light level and the mode in which the camera is operating.
JPEG, TIFF and RAW
The size of the digital file corresponding to the image which the camera produces depends on the pixel count. In most consumer digicams each pixel generates 3 bytes of data (so called “8-bit data”). One for red, one for green and one for blue. This means that a 3MP camera, which has 3 million pixels, generates 9 million bytes of data, or 9MB (megabytes). A few cameras can generate extra data for extra quality, and some of these cameras generate files which correspond to 2 bytes of data for each color (“16-bit”), so a 3MP camera which is capable of generating 16-bit data will produce an 18MB image file.
Now these files are pretty big and they can be compressed quite a lot without a significant drop in quality. This is where JPEG (Joint Photo Experts Group) comes in. JPEG is an algorithm designed to work with continuous tone photographic images) which takes image data and compresses it in a lossy manner (this means you do lose some information). The more you compress, the smaller the file but the more information you lose. However, you can reduce file size by a factor of 10 or so and still get a very high quality image, just about as good as the uncompressed image for most purposes. You can reduce the file size by a factor of 40 - or even more - but the image starts to look really bad!
Some cameras offer a third option, that of saving the actual data generated by the sensor in a proprietary format. Canon calls their version of this “RAW”, Nikon call it “NEF”. These files are compressed, but in a non-lossy manner. They are significantly smaller than equivalent TIFF files, but larger than JPEGs. Typically they achieve a compression of around 6:1 using 16-bit data, so files are 1/6 the size of equivalent TIFF files. Since the RAW and NEF formats contain more information than JPEGs (and in fact often more than TIFF files) you can do some degree of exposure compensation during conversion to JPEG to rescue otherwise improperly exposed images. You can also make white balance corrections during conversion, so if you shot with the wrong white balance, you can fix your error.
Memory
There are quite a few different (and incompatible) memory cards used in digital cameras.
· Compact Flash (CF) - The original memory card. 42mm x 36mm x 3mm
· Secure Digital (SD) - Very small - about 24mm x 32mm and 2mm thick. They have a built in write protect switch to prevent accidental erasure and certain encryption capabilities of little interest to digital camera owners.
· Multimedia - Same size as SD but with less features and no encryption capability..
· Smart Media - Thinner than CF cards, but lacking an on-card memory controller.
· Memory Stick - Introduced by Sony and used only by Sony.
· XD - Developed and used by Fuji, Olympus and Toshiba - even smaller than SD. 20mm x 25mm by 1.7mm thick
Finally you may ask “Is there any real difference in performance? ” The answer is “No, not really”.
Wish you happy clicking.Bye.
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