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Camera Model: NIKON D80

Exposure: 1/60 sec

Focal Number: f/5.6

Focal Length: 135mm 

Camera Model: NIKON D80

Exposure: 1/200 sec

Focal Number: f/18

Focal Length: 70mm

Camera Model: NIKON D80

Exposure: 1/30 sec

Focal Number: f/14

Focal Length: 70mm

Under-expose. This is an under-exposed photo.

Camera Model: NIKON D80

Exposure: 1/60 sec

Focal Number: f/18

Focal Length: 31mm

Over-exposure. This is an overexposed photo. This was taken while the sun was so bright. you almost could not see anything in this image.

Camera Model: NIKON D80

Exposure: 1/5 sec

Focal Number: f/6.3

Focal Length: 24mm

This is the correct exposure of a photo. This was taken using the correct setup of Shutter speed, and aperture size.

Camera Model: NIKON D80

Exposure: 1/250 sec

Focal Number: f/11

Focal length: 48mm

Color of depth of field

F-Number: F/9
Exposure Time: 1/100 sec.
Camera Model: NIKON D80
Focal Length: 40 mm

Depth of Field

F-Number: F/5.3
Exposure Time: 1/160 sec.
Camera Model: NIKON D80
Focal Length: 62 mm

Sandwich

F-Number: F/5
Exposure Time: 1/60 sec.
Camera Model: NIKON D80
Focal Length: 50 mm

Shallow

F-Number: F/5
Exposure Time: 1/40 sec.
Camera Model: NIKON D80
Focal Length: 50 mm

Texture

F-Number: F/5.6
Exposure Time: 1/60 sec.
Camera Model: NIKON D80
Focal Length: 90 mm

Vanishing Point

F-Number: F/5.6
Exposure Time: 1/60 sec.
Camera Model: NIKON D80
Focal Length: 50 mm

Digital photography is a form of photography that uses digital technology to make digital images of subjects. Until the arrival of digital technology, photography used photographic film to create images which could be made visible by photographic processing. Digital images can be displayed, printed, stored, manipulated, transmitted, and archived using digital and computer techniques by the help of softwares, without chemical processing.

Digital photography is one of several forms of digital imaging. Digital images are also created by non-photographic equipment such as computer tomography (by the use of x-ray) scanners and radio telescopes. Digital images can also be made by scanning conventional photographic images.

Analog photography is also one form of photography which is done based on chemical processes (photographic film) or on electronic tubes (TV). This was the main form of photography for much of its history, but is now being replaced by digital photography.

Exposure is the amount of light received by the film or sensor that is measured by seconds and can be computed from EV (Exposure value). It is also determined by how wide the lens diaphragm can be opened which is known as the aperture and how long you can keep the film or sensor exposed which is known as the shutter speed. The effect of an exposure will depend on the sensitivity of the film or sensor.

The exposure generated by an aperture, shutter speed, and sensitivity combination can be represented by its exposure value “EV”. Zero EV is defined by the combination of an aperture of f/1 and a shutter speed of 1s at ISO 100 (1). Each time you halve the amount of light collected by the sensor (e.g. by doubling shutter speed or by halving the aperture), the EV will increase by 1. For instance, 6 EV represents half the amount of light as 5 EV. High EVs will be used in bright conditions which require a low amount of light to be collected by the film or sensor to avoid overexposure.

A photograph with an exposure time of 25 seconds.

A photograph of a night-time sky with an exposure time of 8 seconds.

Exposure compensation is a technique for adjusting the exposure indicated by a photographic exposure meter, in consideration of factors that may cause the indicated exposure to result in a less-than-optimal image. This means that you can adjust the exposure measured by the light meter by telling the camera to allow more light in (positive exposure compensation) or to allow less light in (negative exposure compensation).

Remember, as the aperture size increases, the less light is able to enter the lens.

Shutter is a complicated mechanism that precisely controls the duration of time that light passing through the lens remains in contact with the digital image sensor. The camera’s shutter is activated by the shutter release button. Prior to the digital age, the shutter remained closed to prevent the film from being exposed. Depending on the type of digital image sensor, a mechanical shutter may not be necessary. Rather than a shutter revealing light to initiate a chemical reaction in the film, the digital image sensor may simply be turned on and off.

In photography, shutter speed is the length of time a shutter is open; the total exposure is proportional to this exposure time, or duration of light reaching the film or image sensor.
Shutter speed is the common term for exposure time, the effective length of time a shutter is open; the total exposure is proportional to this exposure time, or duration of light reaching the film or image sensor.

Aperture

The aperture is the size of the “hole” that captures the light into your camera sensor. The wider the aperture the more light that will reach the sensor in a fixed length of time.

Aperture is measures in f-stops each f-stop indicates a number that divides the focal length of the camera lens. For example if your focal length is 28mm an f2 aperture means 28/2 = 14mm of aperture.

For a 50mm focal length an f8 aperture will mean 50/8 = 6.25mm of aperture. If the focal length is fixed the higher the f number the smaller the aperture will be and less light will reach the sensor. When you use a high f number the aperture will be very small meaning just a tiny fraction of light will pass to the sensor so you will probably need longer shutter speeds to reach the right exposure in your picture.

Portrait and object Apertures

When you take a picture of a person or an object you want that person or object to be incredibly sharp and you don’t worry about the rest. For these situations very wide apertures (small f numbers) are perfect.

The smaller the f number the more reduced your depth of field will be producing a focused subject with a blurred background. This effect is called Bokeh. For very wide apertures such as f1.8 or f2 the effect is really intense with a focused object and a completely blurred background. If you need a wider depth of field you can go up to f5.6 depending on what needs to be sharp and what not. The wide aperture also means a lot of light will enter the sensor so you will be able to take good portraits and pictures inside a house without needing to use the flash.

Depth of field (DOF) is the portion of a scene that appears sharp in the image. Depth of field the subject that is acceptably sharp within the range of distance. The depth of field varies depending on camera type, aperture and focusing distance, although print size and viewing distance can influence our appreciation of it. This section is designed to give a better intuitive and technical understanding for photography, and provides a depth of field calculator to show how it varies with your camera settings.

The depth of field does not abruptly change from sharp to unsharp, but instead occurs as a gradual transition. In fact, everything immediately in front of or in back of the focusing distance begins to lose sharpness even if this is not perceived by our eyes or by the resolution of the camera.

CIRCLE OF CONFUSION

Since there is no critical point of transition, the rigorous term called the “circle of confusion” is used to define how much point needs to be blurred in order to be perceived as unsharp. When the region is said to be outside the depth of field and thus no longer “acceptably sharp” it is when the circle of confusion becomes perceptible to our eyes. The circle of confusion above has been exaggerated for clarity; in reality this would be only a tiny fraction of the camera sensor’s area.

When does the circle of confusion become perceptible to our eyes? An acceptably sharp circle of confusion is loosely defined as one which would go unnoticed when enlarged to a standard 8×10 inch print, and observed from a standard viewing distance of about 1 foot.

At this viewing distance and print size, camera manufactures assume a circle of confusion is negligible if no larger than 0.01 inches (when enlarged). As a result, camera manufacturers use the 0.01 inch standard when providing lens depth of field markers (shown below for f/22 on a 50mm lens). In reality, a person with 20-20 vision or better can distinguish features 1/3 this size or smaller, and so the circle of confusion has to be even smaller than this to achieve acceptable sharpness throughout.

A different maximum circle of confusion also applies for each print size and viewing distance combination. In the earlier example of blurred dots, the circle of confusion is actually smaller than the resolution of your screen for the two dots on either side of the focal point, and so these are considered within the depth of field. Alternatively, the depth of field can be based on when the circle of confusion becomes larger than the size of your digital camera’s pixels.

Note that depth of field only sets a maximum value for the circle of confusion, and does not describe what happens to regions once they become out of focus. These regions also called “bokeh,” from Japanese (pronounced bo-ké). Two images with identical depth of field may have significantly different bokeh, as this depends on the shape of the lens diaphragm. In reality, the circle of confusion is usually not actually a circle, but is only approximated as such when it is very small. When it becomes large, most lenses will render it as a polygonal shape with 5-8 sides.