In today's Digital Cameras the Lens is ranked next to the CCD matrix in importance. With the advancement of electronic technology the cost of CCD chips steadily decreases while that of quality optics does not change and now we can say that a good lens is the most expensive component in a digital camera.

It is possible that your digitalkamera is equipped with a good matrix 10 or 12 MP, but if the lens' resolution is insufficient, it wouldn't obtain the most out of this matrix. There are cheap 10 MP digicams, which provide much worse and unfit for printing image than some 5 MP cameras from the recent past with quality professional lenses.

What is important to know about the lens when you buy a camera?



Zoom (variable focal length)

Variable focal length allows you to maximize or reduce captured objects without physically approaching or moving away from them. When checking the values of the parameter zoom in promotional brochures, by all means notice whether it is a true optical or interpolated digital zoom. In the first case, you have real change in the size of objects in the picture, without loss of quality, while in the second the missing pixels are drawn by the camera according to a particular algorithm. Do not let yourself be mislead by the attractive values of digital zoom, optical zoom values are the ones that matter. Digital zoom, you can do later on the computer, with suitable editing program with even better quality than you would have on camera software.

As opposed to amateur film ones, digital cameras using matrices with different physical dimensions, require lenses with different focal lengths to achieve the same zoom, just as cars require different weight according to different engine power, in order to accelerate to the same speed for the same time. For this reason and for ease of comparison of the 35 millimeters equivalent parameter property of lenses of different digital cameras is used. Thus is called the equivalent focal length, which would lead to the same zoom in the classic film 35 millimeters camera.

Focal length is indicated on the lens itself in millimeters as follows f = 6 mm, f = 8 mm or when a zoom lens with a range for example from 7 to 21 mm is shown just 7-21 mm. This means that the lens is a 3 x optical zoom. If the matrix of the corresponding camera is a size 1/1.8 such zoom as scale and magnification of the image corresponds to approximately 35-105 mm camera with film. To the same equivalent focal lengths would correspond a lens 6-18 mm with smaller size of the matrix: 1/2.5. Or assuming that film cameras f = 50 mm focal length is the normal one, in which the image corresponds to what we see with naked eye, then our lens can depart the object approximately 1.3 times (wide-angle lens position) and magnify it around 2 times.

Relative Aperture

This is an important parameter because it determines how you can use your camera in challenging lighting conditions. Typically, a lens has an indication of relative units for a maximum aperture in the following form: 1:2.8, 1:4, 1:5.6, etc. The less the value of the denominator, the more the lens' relative aperture: digicam more suited to obtain quality images in poor lighting conditions. It's good to know that usually the relative aperture decreases with increasing the focal length when working with optical zoom. Therefore, the value of the light power can be noted as follows 1:2.8 - 1:4, meaning that it changes (decreases) 2 times in the longest focal position of the lens in comparison with the wide-angle one.

Optical stabilization

This is one parameter that we might call more "extra" and is common in amateur class digital cameras.
System for optical stabilization (Optical Image Stabilizer - OIS) is crucial for achieving sharp images when light is scarece or when we shot with big zoom when even the slightest twitch of the hand can spoil the picture. The principle of operation is as follows: the lens has a built-in sensors recording every twitch of your hand. They give signals to a system controlling a floating optical element in the lens, which moves for hundreds of a second and compensates for the hand vibration.
It's definitely worth paying a little more for such a function, which would improve the sharpness and quality of images in all lighting conditions.

Finally, speaking of lenses of digital cameras in the amateur class we should mention the possibility of adding wide angle and tele adapters to some digitalkameras. They change the focal length range and achieve greater zoom in or out the objects.