Digital Cameras

Hi you all...
I am little upset today. Raising temp... tropical country... obviously in home... Lots of disagreement commotions... hmmm... what can i do...

Ok lets come to the topic. Today i thought of purchasing a Digital Camera. So as usual i googled some information regarding digicams. Its pretty cool and worth sharing. But i want to make a note that it took a lot of time to find all the information i needed to know regarding the digital cams. This incident only gave me the light to this blog. BRINGING ALL TO ONE ROOF.

Digital Camera:

Steven Sasson was the first engineer to invent a digital camera in Eastmen Kodak in the year 1976 using a charge-coupled device image sensor. These are cameras meant to take digital photographs or even videos utilizing the electronic image sensor. They have their own advantages as they can cover the entire marriage function coverage with a single chip of memory. The awesomeness of digital photography is the ability to show what is taken at that moment. The varied digital quality from its resolution.

Resolution:
               The resolution of digital camera is limited by the image sensor, considered as the heart of the camera (probably a eye, i am not saying, LOL :P) that turns light into discrete signals. The sensor is made of millions of buckets that essentially count the number of photons that strike the sensor. Therefore, the brighter the pixel at a point, the greater the signal at that point. A color filter array may be used depending on the physical structure of the sensor. So the number of resulting pixel determines its pixel count.

Lets say... a 640x480 image would have 307,200 pixels or approximately 307 kilopixels. like wise a 3872x2592 image would have a 10 megapixel size.

The pixel count alone is commonly presumed to indicate the resolution of a camera, but this simple figure of merit is a misconception. Other factors impact a sensor's resolution, including sensor size, lens quality, and the organization of the pixels (for example, a monochrome camera without a Bayer filter mosaic has a higher resolution than a typical color camera). Where such other factors limit the resolution, a greater pixel count does not improve it, but may rather make the digital images inconveniently large and/or exacerbate image noise. Many digital compact cameras are criticized for having excessive pixels. Sensors can be so small that their 'buckets' can easily overfill; again, resolution of a sensor can become greater than the camera lens could possibly deliver.

Look at the small example:

 

Image in the LEFT has a lower resolution than the RIGHT one, but has higher spatial resolution.
So Dont just go for a high resolution cam, see for the spatial resolution.

Spatial Resolution:
                           It is a major determinant of image resolution, we most people dint know this. Really, this is very important while purchasing a camera. Spatial Resolution, also called as angular resolution is the ability of the camera, obviously the CCD sensor to process minute details in the image. Now see the image back. Now you are a PRO !

A image showing A 170px CCD sensor:

It contains a array of pixel sensors with a integrated chip with each pixel having a photo detector and a active amplifier. A charge-coupled device (CCD) is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time. CCDs move charge between capacitive bins in the device, with the shift allowing for the transfer of charge between bins.






Method of image capture:
                                     Based on the hardware configuration of the sensor and the color filter, the method of capture falls into 3 basic category: 


1. Single Shot:
                     Single-short system uses either one CCD with bayer filter mosaic, or three separate image sensors, those RGB combinations employing a beam splitter.


2. Multi-shot:
                   In this method, the camera aperture is opened multiple times to capture separately the RED then BLUE and GREEN image data. There is also a term called Microscaning, where a bayer filter is used and final image sets are stitched together to form a higher resolution pictures.


3.Scanning:
                This is more or less like a Desktop scanner. In this the sensor moves across the focal plane.

BUT... The choice of method of capture is Subject depend. It is usually inappropriate to attempt to capture a subject that moves with anything but a single-shot system. However, the higher color fidelity and larger file sizes and resolutions available with multi-shot and scanning backs make them attractive for commercial photographers working with stationary subjects and large-format photographs.

Dramatic improvements in single-shot cameras and raw image file processing at the beginning of the 21st century made single shot, CCD-based cameras almost completely dominant, even in high-end commercial photography. CMOS-based single shot cameras remained somewhat common.

Types of cameras:

               Digital cameras are made in a wide range of sizes, prices and capabilities. The majority are camera phones, operated as a mobile application through the cellphone menu. Professional photographers and many amateurs use larger, more expensive digital single-lens reflex cameras (DSLR) for their greater versatility. Between these extremes lie digital compact cameras and bridge digital cameras that "bridge" the gap between amateur and professional cameras. Specialized cameras including multispectral imaging equipment and astrographs continue to serve the scientific, military, medical and other special purposes for which digital photography was invented.

1. Compact Digital Cameras:

Compact cameras are designed to be tiny and portable and are particularly suitable for casual and "snapshot" uses. Hence, they are also called point-and-shoot cameras. The smallest, generally less than 20 mm thick, are described as subcompacts or "ultra-compacts" and some are nearly credit card size.^[8]

Most, apart from ruggedized or water-resistant models, incorporate a retractable lens assembly allowing a thin camera to have a moderately long focal length and thus fully exploit an image sensor larger than that on a camera phone, and a mechanized lens cap to cover the lens when retracted. The retracted and capped lens is protected from keys, coins and other hard objects, thus making it a thin, pocketable package. Subcompacts commonly have one lug and a short wrist strap which aids extraction from a pocket, while thicker compacts may have two lugs for attaching a neck strap.

Typically, these cameras incorporate a nearly silent leaf shutter into their lenses.Compact cameras are usually designed to be easy to use, sacrificing advanced features and picture quality for compactness and simplicity; images can usually only be stored using lossy compression (JPEG). Most have a built-in flash usually of low power, sufficient for nearby subjects. Live preview is almost always used to frame the photo. Most have limited motion picture capability. Compacts often have macro capability and zoom lenses but the zoom range is usually less than for bridge and DSLR cameras. Generally a contrast-detect auto focus system, using the image data from the live preview feed of the main imager, focuses the lens.

For lower cost and smaller size, these cameras typically use image sensors with a diagonal of approximately 6 mm, corresponding to a crop factor around 6. This gives them weaker low-light performance, greater depth of field, generally closer focusing ability, and smaller components than cameras using larger sensors.

Starting in 2011, some compact digital cameras can take 3D still photos. These 3D compact stereo cameras can capture 3D panoramic photos for play back on a 3D TV. Some of these are rugged and waterproof, and some have GPS, compass, barometer and altimeter.

2.Bridge Cameras:

 Bridge are higher-end digital cameras that physically and ergonomically resemble DSLRs and share with them some advanced features, but share with compacts the use of a fixed lens and a small sensor. Like compacts, most use live preview to frame the image. Their autofocus uses the same contrast-detect mechanism, but many bridge cameras have a manual focus mode, in some cases using a separate focus ring, for greater control. They originally "bridged" the gap between affordable point-and-shoot cameras and the then are not affordable earlier digital SLRs.

Due to the combination of big physical size but a small sensor, many of these cameras have very highly specified lenses with large zoom range and fast aperture, partially compensating for the inability to change lenses. On some, the lens qualifies as super-zoom. To compensate for the lesser sensitivity of their small sensors, these cameras almost always include an image stabilization system to enable longer handheld exposures.

These cameras are sometimes marketed as and confused with digital SLR cameras since the appearance is similar. Bridge cameras lack the reflex viewing system of DSLRs, are usually fitted with fixed (non-interchangeable) lenses (although some have a lens thread to attach accessory wide-angle or telephoto converters), and can usually take movies with sound. The scene is composed by viewing either the liquid crystal display or the electronic viewfinder (EVF). Most have a longer shutter lag than a true dSLR, but they are capable of good image quality (with sufficient light) while being more compact and lighter than DSLRs. High-end models of this type have comparable resolutions to low and mid-range DSLRs. Many of these cameras can store images in a Raw image format, or processed and JPEG compressed, or both. The majority have a built-in flash similar to those found in DSLRs.

In bright sun, the quality difference between a good compact camera and a digital SLR is minimal but bridge cams are more portable, cost less and have a similar zoom ability to DSLR. Thus a Bridge camera may better suit outdoor daytime activities, except when seeking professional-quality photos.

In low light conditions and/or at ISO equivalents above 800, most bridge cameras (or megazooms) lack in image quality when compared to even entry level DSLRs. However, they do have one major advantage: their much larger depth of field due to the small sensor as compared to a DSLR, allowing larger apertures with shorter exposure times.

A 3D Photo Mode was introduced in 2011, whereby the camera automatically takes a second image from a slightly different perspective and provides a standard .MPO file for stereo display.

3.Digital Single Lens Reflex Cameras:

Digital single-lens reflex cameras (DSLRs) are digital cameras based on film single-lens reflex cameras (SLRs). They take their name from their unique viewing system, in which a mirror reflects light from the lens through a separate optical viewfinder. At the moment of exposure the mirror flips out of the way, making a distinctive "clack" sound and allowing light to fall on the imager.

Since no light reaches the imager during framing, auto-focus is accomplished using specialized sensors in the mirror box itself. Most 21st century DSLRs also have a "live view" mode that emulates the live preview system of compact cameras, when selected.

These cameras have much larger sensors than the other types, typically 18 mm to 36 mm on the diagonal (crop factor 2, 1.6, or 1). This gives them superior low-light performance, less depth of field at a given aperture, and a larger size.

They make use of interchangeable lenses; each major DSLR manufacturer also sells a line of lenses specifically intended to be used on their cameras. This allows the user to select a lens designed for the application at hand: wide-angle, telephoto, low-light, etc. So each lens does not require its own shutter, DSLRs use a focal-plane shutter in front of the imager, behind the mirror.

So finally after all theories and confusions regarding digital cameras, I decided not to buy anything now.

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Courtesy: Wikipedia.org