Basic Photography

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Basic photography tips

There are three technical elements that "make" an image

Aperture
Shutter speed
ISO speed (sensitivity of the digital sensor)

1. Aperture

aperture schema

The aperture determines the amount of light that gets to the digital sensor. A SMALL number indicates a LARGE aperture, good lenses start with a maximum aperture of 2, better and more expensive lenses start at 1.1!

Apart from the quantity of light that is allowed to get through, the aperture also determines the DOF (depth of field).

The numbers you see on the side of a lens usually look like this:
F 22 | 16 | 11 | 8 | 5.6 | 4 | 2.4

At F 22, the lens lets in a very small amount of light, it is at minimum aperture. At F 2.4, the lens lets in the maximum amount of light that it has been designed for.

Each number represents a double increase (or decrease) of the quantity of light that is allowed through the lens.

For example: at aperture 5.6 you allow 2 times more light than at aperture 8, and 2 times less light than at aperture 4

On "point and shoot" digital cameras you do not see this numbers on the side of the lens, the process of opening and closing the aperture is controlled electronically and has also increments like: 5.9 or 8.2
2. Shutter speed

The shutter is the device that controls the exposure time of the photo. The exposure time usually begins at 1/2000 sec. and goes up to 30 sec.

At 1/250 sec. exposure time, the shutter will let in 2 times more light than at 1/500 sec. and 2 times less than at 1/125 sec.

The exposure time determines how a photo will look, if it will be "shaken" or crystal clear. For example: you want to take a picture of a water fountain. You have two options, use a short exposure, or a long one. A short exposure (of 1/2000 sec.) will "freeze" the water droplets in mid air; the detail of every droplet will be clearly visible in the photo. A long exposure time (of 1 sec.) will create a special effect where the falling droplets traces unite to create streams of water.

Aperture Priority | Shutter Speed 1/25 | Aperture Value 8 | ISO Speed 50

Aperture Priority | Shutter Speed 1/1000 | Aperture Value 3.2 | ISO Speed 50

3. ISO speed

ISO speed is the third element that "makes" a photo. It is usually expressed with the following numbers:
50 | 100 | 200 | 400 | 800 | 1600 | 3200

These numbers tell you how "fast" does the digital sensor react to the light sent through the aperture and shutter.

A small number means that it takes a relatively long time to take a photo, a large number, a very short time.

But things are relative in using the right ISO setting. On an average digital camera, the ISO goes from 50 to 400. The ISO speed 50 is usually used on bright sunny days, while the 200 and 400 ISO is used in low light conditions (like interiors or at night)

There is also a problem with the image quality regarding the ISO speed. At large numbers, 400, 800, the image will contain "noise", so use the low ISO speed as much as possible.

Here is a table that will further explain how the aperture, shutter speed and ISO speed are used TOGHETHER to "make" an image. I'll give a theoretical example of how this three indicators work together: At ISO speed 100 you select an aperture of 8 and the shutter speed is calculated by the camera at 1/250 sec. The same image*, mathematically speaking, can be created using the following settings:
ISO speed Aperture Shutter speed
100 16 1/60
100 11 1/125
100 8 1/250
100 5.6 1/500
100 4 1/1000

same image* - the same in theory but with different effects on the final, real image

As you can see, with the ISO speed constant, the aperture and exposure time increase or decrease in connection with each other; if the aperture allows more light into the camera, the shutter speed decreases to compensate and give the perfect exposure.

But what happens to these theoretical numbers if you set the ISO speed at 50? Take a look:
ISO speed Aperture Shutter speed
50 11 1/60
50 8 1/125
50 5.6 1/250
50 4 1/500
50 2.8 1/1000

You can modify the aperture, keeping the shutter speed constant, or you can modify the shutter speed, while keeping the aperture values constant:
ISO speed Aperture Shutter speed
50 16 1/125
50 11 1/250
50 8 1/500
50 5.6 1/1000
50 4 1/1250

full copyright, text&images © www.digital-cameras-help.com / published: January/20/2006