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diagrams illustrating sensor types. bit depth and digital noise

‘Capture’ Group Questions

camera sensors are a piece of hardware within the camera body that capture and convert light (photons) into digital information, forming an image. the camera sensor gathers photons using photo sites, small wells on the surface of the sensor that gather the photons while the camera’s shutter is open. once the cameras shutter has closed the camera uses the varying electrical signal strengths created by the photons within the photo sites converting them to a digital value which is collated to form a digital image. photo sites require coloured filters to distinguish colour. these filters block colours of light that are not their own. these filters are grouped together in grids of 4 by 4 known as a Bayer array this allows the camera to replicate more complex colours than just red, green and blue. by measuring the different brightness or volume of each individual RGB colour that makes up the more complex colour and combining this information together the processor can create an approximation of the colour based on the brightness of red, green or blue present. their are variations in sensor design. the two most prominent are CMOS (complementary metal- oxide semiconductor) and CCD (charge coupled device) sensors. initially CCD sensors were the superior of the two with much better image quality and less noise whereas the CMOS sensors where seen as a tad lacklustre with poorer image quality. though, as is still the case, the CMOS sensors had better power efficiency than the CCD sensors. CCD sensors record the pixel information during exposure and send each pixel to be processed one after the other which is energy inefficient on account of the fetching and sending taking place it is also more time consuming than the CMOS alternative. in CMOS sensors the information captured during light exposure is gathered within the sensor itself and sent at once to the processor, reducing energy usage and increasing the speed of the operation. CMOS sensors have lower light sensitivity than CCD sensors, this is because of the increased circuitry present on the CMOS sensor. another sensor type is the foveon sensor. the foveon sensor foregoes having a bayer array and instead has layers of photosensitive diodes stacked on top of each other one for blue, green and red. every photosite is sensitive to the three RGB colours. the concept behind the foveon sensor is that by stacking the photosensitive diodes instead of having them side by side as in a Bayer filter each individual pixel has greater colour accuracy, as each pixel is registering both red, green and blue at once.

photographic dynamic range is the ratio of strongest signal (maximum signal) to weakest signal (noise floor) , this determines the range of highlights and shadows a camera sensor can capture. most DSLRs have a higher dynamic range than compact cameras. the greater the sensor size and pixel size the greater the dynamic range.

bit depth determines how much tonal information each primary (RGB) colour channel can display per pixel. this is important as it determines the tonal range of each colour in the image, the greater the bit depth the wider the range of available tones avoiding problems like image banding where there is little to no graduation between tones. the standard bit depths are 8-bit. 12-bit, 14-bit and 16-bit. bits themselves are a way of storing information. they are binary digits, expressed as 0 or 1, each value equates to a tone, so a 1 bit image would have 2 tonal values black and white, this increases greatly as you increase the bit depth with a 2 bit image displaying 4 tones ( black, white and 2 greys) an 8 bit image displaying 256 tonal values or 16.7 million colour combinations.

digital noise is distortion in an image caused by random variations in the brightness and tone of pixels causing grainy or blotchy patches and aberrant colour. the two main types of noise are colour and luminance noise. colour noise creates blotches of unwanted colour throughout the image, it is often caused by the camera’s sensor overheating. luminance noise is the more frequently encountered of the two and looks like graininess in the image, it is caused by low light shooting and high ISO . the amplification of the images signal caused by increasing ISO also amplifies any noise in the image, the lower the ISO the less noise you should see in the image. some noise can also be generated by overuse of the camera which heats the sensor, hot surroundings or simply from converting the information from pixels to digital information. as discussed before certain sensor types generate more noise. noise reduction can be applied in the menu settings of some cameras, which proves useful for low light or slow shutter speeds.

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Capture Group Questions

Different types of Camera Sensors

CCD - Charged- coupled device. This type of sensor is not often seen in modern cameras, as it was primarily used in the manufacturing of the first-ever digital cameras in the 1970s. This type of sensor was used for photographing images with minimal noise due to the noise control capabilities of this sensor. This type of sensor does create high-quality images, however, since this kind of sensor was used in the first digital cameras, in modern times this type of sensor technology is outdated in the current models of DSLRs, however, are widely used in medium format cameras.

Bayer Sensor - This kind of sensor is seen in most DSLR cameras today is known as the Bayer sensor. Sensors are composed of many photosensors capturing light intensity, however, these photosensors are unable to capture wavelengths of light. The Bayer works as a resolution for this as it overlays the sensors with a microfilter allowing the photosensors to capture the wavelengths of light. This set is made up of a mosaic pattern of four colour filtered sensels; two green, one red, and one blue. These sensels work to calculate the colour information entering the sensor

CMOS Sensor - Cmos sensors are similar to that of CCD's but have advancements, making them more functional than CCD sensors. This kind of sensor is best suited for high-speed capture which is predominantly done on up to date DSLR's, this is due to the reduced power which this kind of sensor uses, this does not affect its efficiency in working.

Foveon X3 Sensor - The Foveon was created by Sigma and is used in their products. The sensor was created based on the technology of the aforementioned CMOS sensor. This sensor eliminates the Bayer filter and in its place has three layers of silicon in which shorter wavelengths absorb closer to the surface while longer ones travel further

Dynamic Range

Dynamic range is the difference between the two extremes: the minimum light intensities (black), and the maximum light intensities (white). It is the difference between what your eye can see and what the camera can see, the tones between black and white. The higher the dynamic range, the more detail there will be in the highlights and shadows. The dynamic range of an image changes depending on what you are displaying the image on, as different devices whether it be capture or display device as each device has a different dynamic range. Dynamic range is measured in stops, 14 stops are considered good for a camera, however, the naked human eye can capture around 20 stops of dynamic range. Dynamic range is important to photographers as you do not want to lose detail in the highlights or details in the shadows. You want to capture a wide array of tones.

Bit Depth

Bit depth is the colour information stored in an image, therefore the higher the bit depth of an image, the more colour information it has. For example, a 1 bot image can only store 2 colours, black and white. While an 8-bit image can store 256 colours, and a24 bit image can store over 16 million colours. This is then important to photographers as the higher the bit depth, the richer and more expansive the range of colours can be, making the images truer to how they were in the mind of the photographer. This is especially important when it comes to the exportation of files. When you save an image, you have control over the bit depth in which the image will save. However, making saving the file in a smaller size can reduce the image quality.

Digital Noise

Digital noise is a visual distortion that occurs under low light conditions when measures must be taken to increase the image, mainly when the ISO must be increased, often taking the form of grain.

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Capture and output name as many different types of Output that photographers use? (group question). How many different paper types & surfaces can your group name and explain some of the key differences? (group question). Paper types: glossy- shiny finish, increased colour saturation and vibran...

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