Do you have some knowledge on CPL filter and PL filter? In this article, I’d like to share what I know:
The polarized light is harmful in photography. The reflected light on the surface of the glass prevents us taking pictures for something inside the showcase. The reflected light on the water prevents us taking pictures for the fish, and it also makes the green leave turn white. Without the polarized light, the pictures will become clear and more beautiful. Then, PL filter is used. Mount the PL filter on the front of the lens, and rotate it until well suited, which minimize the glare as well as some non- polarized light.
How does the polarized light produce? In AF and AE digital cameras, some light will be reflected to the metering element. If the light is reflected from the semireflecting mirror, and the semireflecting mirror is coated with non-metal material, then, the reflected light is polarized light. In these digital cameras, if the common PL filter is used, the performance may not be good, since the angle will affect the reflection of the light, if the angle is not focused correctly, the light can not be reflected successfully. Besides, the LCD display of some digital cameras is illuminated by lens, if the lens use PL filter, the LCD display can not work. In this case, CPL filter should be used. CPL filter is made up with two parts, the front part is a common PL filter used to filter the polarized light in the certain direction, and the back part is able to make the polarized light move in a circle. Therefore, it is named CPL filter.
The CPL filter is much more expensive than that of PL filter. Whether the digital camera use CPL filter or just PL filter, some tests should be made:
Check AF: Rotate the PL filter in different directions, half-press the shutter button and autofocus. If it is able to autofocus in any direction, you just get a PL filter to fulfill the AF function. If not, you should buy a CPL filter.
Check AE: Mount the PL filter in front of the lens, and meter the white wall. If there are different light values, you should buy CPL filter. If there is no problem with the AE and AF, PL filter is OK.
