Photography is derived from the greek word photographia. Photo meaning light, graphia meaning to curve. It means writing with light.
And a Camera is derived from Latin word Camera Obscura which means "dark chamber". More on how this was used back in time to capture images and how it lead to photography can be found here.
Types of Cameras
There are two types of cameras,
- Film Based - uses film to capture the images. Maximun exposure of 36 images per roll of film
- Digital - uses sesnor to capture the images. It cannot retain the images like the film. With a 1GB memory card, 256 JPEG images can be taken which are of 4MB each.
What is a Single-lens reflex camera?
A digital single-lens reflex camera (digital SLR or DSLR) is a digital camera that uses a mechanical mirror system and pentaprism to direct light from the lensviewfinder on the back of the camera. "SLR" means that the same lens is used for viewing and taking pictures. A mirror in the body directs the light from the lens up into a prism for viewing, then flips up out of the way just before an exposure is made. to an optical 
A cross-section (or 'side-view') of the optical components of a typical SLR camera shows how the light passes through the lens assembly (1), is reflected by the mirror (2) and is projected on the matte focusing screen (5). Via a condensing lens (6) and internal reflections in the roof pentaprism (7) the image appears in the eyepiece (8). When an image is taken, the mirror moves upwards from its critical 45 degree angle in the direction of the arrow, the focal plane shutter (3) opens, and the image is projected onto the film or sensor (4) in exactly the same manner as on the focusing screen. An image is turned upside down each time it is reflected from a mirror.
Old analog cameras had a prism for (7) which made them heavy. With digital cameras this pentaprism is made of just two mirrors which makes it lighter.
Types of Digital Cameras
- Compact/ Consumer eg., Mobile cameras
- Bridge/ Prosumer eg. Digital point and shoot cameras
- DSLR
Both compact and bridge cameras have the lens fixed to the body. With DSLR these are detachable.
Sensor
A device that measures physical quantity of light and converts it to a signal that can be read by the instrument.
Sensors, like film, are sensitive to light. Once the shutter is pressed, they record an image digitally. The size and type of light sensor are significant. It’s clear there’s an obvious physical size difference between a point and shoot camera and a DSLR. This is predominately due to size of the sensor contained in the camera. The sensors found in DLSR models are much larger than those within point and shoot cameras, thus producing clearer images with less distortion and noise.
Sensor Types
- CCD Charged Coupling devices
- CMOS Complementary Mutual Oxid Semiconductor
- Foveon
CCD sensors produce high quality images, although cameras equipped with this sensor tend to be more costly and consume more power than other types.
A CMOS sensor is larger than a CCD sensor so its surface is capable of capturing more light. As a result, CMOS sensors are more sensitive and produce images higher in quality compared to CCD sensors. CMOS sensors are easier and less costly to manufacture and use less power than CCDs. Because of their increased size, cameras using this type of sensor tend to be bulkier.
There has been some debate concerning the relative strengths of CCD versus CMOS. In practice, neither is “better”; each type works effectively and should be evaluated on its own merits.
CMOS is a proprietary of Canon. Nikon pays royalty to Canon for using CMOS sensors.
Sensor Size
The sensor size affects many factors in your images and the functions of your camera body. It has a major impact on the quality of your image, how your lens functions, and how it performs in low light conditions.There are three basic size categories for sensors:
- Four Thirds
- APS
- Full Film Format ( Fx ) - A sensor whose size is equal to the film size i.e, 36 mm * 24 mm. DSLRs with this type of sensor are the costliest and can cost more than 3 lakhs.
Nikon D5000 sensor size is 23.6 * 15.8. Which is half of Fx format, hence known as Dx format. Right now in the market Nikon has the best senor size when compared to others. Four Thirds sensors have become a standard for Olympus and Kodak at a size of 13.5mm by 18mm, while APS sensors are close to that of the original APS film size. Most DSLR cameras fall into the APS size range.
This commonly used term denotes the size ratio between a smaller sensor and a full frame 24X36mm sensor. For example Nikon D5000 with a sensor size of 23.6 * 15.8 the crop factor is 1.5x. The crop factor is most often used to determine the "35mm equivalent" field of view for any given lens when used on a camera with a sensor smaller than 24X36mm.;
Pixel
A pixel is a picture element which is the smallest piece of information. Pixels are square in shape and can have only one color.
File Formats
- JPEG Joint Photographic expert group
- TIFF Tagges Image File Format
- RAW Also called Digital Negative
JPEG format has a lossy compression whereas TIFF has loss less compression. With RAW there is no compression. JPEG and TIFF are already processed by the digital cameras. RAW images are not processed and softwares like photoshop can be used to process these images for the correct exposure.
Memory Cards
- SD
- CF
- Meomory Stick Pro/ Duo [ Proprietary of Sony ]
- MMC
CF are the best due their higher buffer speeds.
Functions of a Digicam
Aperture controls light and depth of field [ DOF ].
Shutter controls light and motion.
The aperture of a lens is the diameter of the lens diaphragm opening and is usually controlled by an iris. The larger the diameter of the aperture, the more light reaches the film / image sensor.
Aperture is expressed as F-stop, e.g. F2.8 or f/2.8. The smaller the F-stop number (or f/value), the larger the lens opening (aperture).
NOTE: Auto/ Program modes on the camera give the median which is f/8.
shutter speed is ‘the amount of time that the shutter is open’. It is the length of time that the sensor ’sees’ the scene you’re attempting to capture. Shutter speeds range from 1/8000, 1/4000, 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1 or -1, -2 etc., measured as a fraction of second. All shutter speeds after 1/60 need a tripod support.
The aperture diaphragm of a lens (bigger or smaller values) AND timing (open and close) of the camera's shutter curtain - BOTH perform the tasks of regulating the amount of light entering the camera and expose onto the film.
*** Fast Shutter speeds freeze motion, slower shutter speeds blur the motion
Exposure
Exposure is the quantity of light allowed to act on the sensor by a product of intensity ( controlled by aperture) and the duration ( controlled by shutter). There is no perfect exposure, but correct exposure.
ISO Sensitivity
On most digital SLR’s (Single Lens Reflex) cameras today you can even change the sensitivity of the sensor when collecting light which is called the ISO speed. The common span of ISO speed is 100 to 800. The higher the ISO speed the faster the camera collects light but it also adds more noise to the photograph than the lower speeds.
Exposure Triangle
The exposure triangle explains how the individual aspects of exposure (aperture, shutter speed and ISO) affect the final exposure of the photo.
A properly exposed photo should (normally) resemble the brightness of the original scene. A poorly exposed photo will either be too dark or too bright and may contain areas that are so dark or bright that they contain no detail (know as blown out). So how can we control the exposure of a photo? That is where the exposure triangle comes in.
The exposure triangle is a useful way of describing the relationship between the three aspects of exposure. Each corner of the triangle represents one of the three variables, aperture, shutter speed and ISO. Adjusting just one of these will make the photo darker or brighter and will change the appearance of the photo based on what you have changed. E.g. using a longer shutter speed will introduce motion blur to your photo but also make the photo brighter (increased exposure) due to more light hitting the sensor. The easiest way to understand it is to see the picture.
White Balance
The easiest way to describe white balance is by way of colour temperature which in itself is a way of measuring the quality and intensity of a light source. This is based on the ratio of blue and red light hitting the sensor, with the green light being ignored. Measured in units of degere Kelvin (K).
Correct day light solur temperatire is 5500k.
Here are some of the basic White Balance settings you’ll find on cameras:
- Auto – this is where the camera makes a best guess on a shot by shot basis. You’ll find it works in many situations but it’s worth venturing out of it for trickier lighting.
- Tungsten – this mode is usually symbolized with a little bulb and is for shooting indoors, especially under tungsten (incandescent) lighting (such as bulb lighting). It generally cools down the colors in photos.
- Fluorescent – this compensates for the ‘cool’ light of fluorescent light and will warm up your shots.
- Daylight/Sunny – not all cameras have this setting because it sets things as fairly ‘normal’ white balance settings.
- Cloudy – this setting generally warms things up a touch more than ‘daylight’ mode.
- Flash – the flash of a camera can be quite a cool light so in Flash WB mode you’ll find it warms up your shots a touch.
- Shade – the light in shade is generally cooler (bluer) than shooting in direct sunlight so this mode will warm things up a little.
The following values are approximate but should give you an idea of how this is seen in most photographic situations.
Light Source | Colour Temp in K |
Clear Blue Sky | 9,000 to 15,000 |
Overcast Sky | 6,000 to 8,000 |
Noon Sun and Clear Sky | 6,500 |
Sunlight Average | 5,400 to 6,000 |
Electronic Flash | 5,400 to 6,000 |
Household Lighting | 2,500 to 3,000 |
200-watt Bulb | 2,980 |
100-watt Bulb | 2,900 |
75-watt Bulb | 2,820 |
60-watt Bulb | 2,800 |
40-watt Bulb | 2,650 |
Candle Flame | 1,200 to 1,500 |
