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Polarization filter - test.

2. Introduction part 2

2007-04-25

Some models have active function of showing the information about the exposure (an aperture, shutter speed, sometimes ISO). This information can help us determine the power of filter if it is greater or not. It's even easier to determine e.g. in the semi-automatic mode when we can set the aperture stop to the full value e.g. F/6.3 (not every camera have it available in the semi-automatic mode). But, almost every camera, if not everyone, has the function of aperture preselection, which allows setting of the constant aperture value and the depth of field thereby. In this mode the camera will set the shutter time when we push the shutter button to the half and the photo will be exposed properly (obviously to the best of its abilities).

In this situation there is a possibility that we have to extend the exposure time above tho 1/60 sec. if we want to have the correct exposure. The camera will set the shutter, but then there is a risk that the photo taking "from the hand" can be moved and the tripod will be necessary. You can also support the camera by the parapet or switch on a flash. The solution we choose depends on the conditions in which we photograph and on the quality of our camera.

I know the date above are quite general but every camera have to be described apart in order to give the certain parameters which cause the problem of the motion blur. I don't have such a intent here. One camera has the image stabilization option and the other will switch on the flash automatically. It's necessary to get to know with the manual instruction and the technical specification to learn which solution is available. The important thing is the set of the consent value of the aperture (freestyle) in order to determine if the shutter time changes while the polarization filter is being rotated. The pictures below was taken in such a way that this difference is visible. For the teaching purpose I give shutter time and the value of the aperture.

I took this photographs in different weather conditions (in the sun, clouds, clouds - visible little shadow, shadow) and in different places (open area, greenery and sky, water) and I set the camera in the different angles to the falling sunshine (30, 90, 130, 0 degrees - with the sun at the front 180 degrees with the sun behind). Information about it I give also next to the pictures and every photo was taken in three copies (maximum filter, minimum filter without polarization filter).

The photography taken in the partial sun - the sky partial cloudy, the angle between the lens axis and the falling sunshine 90 degrees

fot. 3 full polarization (1/250 f/6.3)	fot. 4 without filter (1/1000 f/6.3))	fot. 5 minimal polarization or without it (1/400 f/5.6)

The pictures 3 and 5 was taken with the filter - the time is significantly longer then in case of the photo without the filter (pic. 4). Moreover the difference between the photo 3 (full polarization) and photo 5 (minimal polarization or without it ) is seen. The effect of warming of the greenery on the photo 3 and the clear separation the cloud from the sky, which is darker is seen.