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Polarization filter - test.

1. Introduction

2007-04-25

The polarization filter is the part of the extra equipment which can be attached to the lens in order to a correction or modification of the photo. It consist of the two glasses and one of them can be rotated around the other. The greater or smaller polarization effect depends on their position. The minimal polarization (min) or lack of it can be obtained when the glass is angled to 90 degrees to the right or left from a place where the maximal polarization is observed (max). The position of the maximal polarization effects in the warmer colours on the photo and in the reduced light reflexes in the water and glass or even in the plants and other objects. Using this filter we can make the grass more green and the sky more blue. The contrast also will be greater.

The users of the compact cameras will have the more difficult task because the effect of changed polarization in the electronic viewfinder or in the display is not as visible in the optical viewfinder, which is mainly used in the SLR cameras. In the viewfinder which not "look through" the lens there won't be any modification of the polarization, because we won't look through the filter in this situation. Then, we just can rely on the screen to preview the effects of the filter work.

The two types of the filters are distinguished: circular and linear. The differs in the invisible for naked eye structure and in the price (the linear is cheaper). The circular filter is using to the SLR cameras, because only it assure the right camera work. The compact cameras work correctly with the both types. As I mentioned the linear is cheaper and the effect is the same.

The power of the filter depends on the angle between the direction of falling light and the direction where we "aim" the camera. We can expect the greatest polarization with the angle of 90 degrees (with the light o the side). The lowest effect will be obtained with the sun at front of us or behind us. Is the same with the sun intensity - the effect will be greater in the full sun and the lower in the shadow and the lowest, almost invisible, in the cloudy day (everything depends on the quality of the light. If it's fading the effect will be low)

In addition we can expect the higher polarization when we are in higher place, e.g. in the mountains. Sometimes when it's cloudless day in a the mountains standing with the sun at the side we can exaggerate setting the filter on the maximal position. The effect will be unnatural.

The interesting fact is possibility to "switch off" the polarized light with the again polarization by the polarization filter. In this way we can "switch off" e.g. the activated LCD monitor which will be totally black on the photo. (pict. 1, pic.2).

pic. 1 whithout polarization (1/60 f/2.2)	pic. 2 full polarization (1/2.5 f/4.5)