bytes, chips, digits & dots.
Since the advance of digital photography manufacturers of cameras, printers, computers and memory cards (just to name a few) are boxing consumer’s ears with an indistinct terminology.
Let’s try to explain all these trendy but puzzling expressions before you dig into the world of digital photography. Below you'll find an explanation, too, of the sensor types Nikon is using in its digital cameras. Have a look here for the various chip sizes.
Bit = this unit of information in computing contexts is a blend of binary and digit.
Binary = two digits; 0 and 1 (in a specific order) are used in computer world to ‘translate’ letters and signs for further processing. A computer (= Latin: computare = adding up) in fact is a very fast calculator!
Digit = (Latin: digitus = finger) numeral counting 0 – 9.
Byte = a group of (in most cases 8) bits. The term byte was invented by Werner Buchholz in 1956 and was used to encode a single character of text.
Dots = small marks or drops of ink that make/form an image.
Pixels = 1. light sensitive diodes on a sensor. 2. dots
Every letter or sign that you see on a computer screen is saved on a memory device in a group of many 0’s and 1’s (binary system). If they are saved while making use of a file of twelve 0’s and 1’s (for each letter or sign in a specific order) we’ll have a 12-bit file.
The sensors in digital cameras have many light sensitive diodes that catch the incoming light. All these diodes are also called pixels. So, a camera with a sensor with 12 million pixels (12 Mp.) will have a sensor with 12 million of individual light sensitive diodes. In some cameras these diodes are coupled in groups of two, three or four. E.g. a Nikon D1 has a sensor with 10.8 million pixels, but coupled in groups of four diodes. Thus the camera’s sensor has 2.7 effective Mp.
An image is shown on a screen or printed on paper in millions of dots. The more dots per square inch the sharper and the more detailed the image will be.
people get excited when they speak about the number of pixels. "The
more pixels the better the camera, and the image it will produce"
is an often heard and ineradicable statement! The number of pixels
is not the gospel truth, however! The size of the sensor, the size
of the pixels and their arrangement, the way of processing image
data, the built-in processing unit and many more hard and soft ware
inside a camera are important elements to determine whether a camera
is the best or not. Most sensors used by Nikon Corporation are made
by others (mainly Sony) but not without the finishing touch of Nikon
used in Nikon digital cameras.
CCD stands for 'charged coupled device' and is nothing more than a rectangular metal chip/plate with millions of photosensitive receptors aka photo-diodes. If the receptors are catching light they produce an electric charge. As all receptors are insensitive to colours each receptor has a colour filter on top. Only the three primary colours (red, green and blue) are used. The charge of each receptor is read - via a process called demosaicing - by a tiny built-in computer and converted into a digital image file. Not only the number of receptors is important, also the size and shape of the receptors are playing an important role. Receptors can be square, rectangular or octagonal in shape and can be placed in a horizontal, vertical or diagonal line/row. Most CCD sensors are covered by one or more filters. The most important filter is a filter with the Bayer*-pattern, dividing various colours and filtering infrared and blocking light beams that reach the receptor at angles of 90° and more.
* named after Bryce Edward Bayer (1929-2012) an Eastman Kodak research scientist.
C-MOS stands for 'complementary metal-oxide semi-conductor' sensor. The production of a C-MOS sensor is a bit cheaper and the way the receptor information is read differs. A C-MOS sensor can produce a bit more 'noise**' and in older sensors RAW-output may be slightly filtered. Positive elements are the quick start-up and low power consumption. As all receptors are surrounded by hardware (transistors etc.) each receptor may carry a wide-angle lens to 'close' the space between the receptors.
** noise is a collective noun for various influences and effects, caused by heat, radiation, false light etc.
These letters stand for 'lateral buried charge accumulator and sensing transistor array'. A mouthful for a 'home made' (by Nikon) sensor with junction field effect transistors (JFET). The receptor read-out is faster, less noise and low power consumption are the most important features of this sensor, which has been put in the Nikon D2H and Nikon D2Hs digital reflex cameras, only! Never used again in whatever digital camera since! To produce a sensor by yourself may be an expensive exercise, while others (Sony and Fuji) have plenty very nice sensors on the shelf.
Image File Formats
To save images on a memory device various coding and filing systems were invented. The most used are:
DCF = Design Rule for Camera File system
DPOF = Digital Print Order Format
EXIF = Exchangeable Image File format for digital still cameras
NEF = Nikon Electronic File
JPEG = Joint Photographic Experts Groups created in 1986 for coding still pictures
TIFF = Tagged Image File Format
SD = Secure Digital memory card
CF = Compact Falsh mnemory card
LCD = Liquid Crystal Display
TFT = Thin-film Transistor used in LCD screens to improve image quality