In this article I will take a look at some filters used in photography, as well as some filter for Xiaomi Yi action camera with several mounting options:
At first let’s take a look at some filters:
They prevent getting ultraviolet light (UV) from getting through. In photography they are used to reduce the level of ultraviolet light that strikes the recording medium.
Photographic films were sensitive to UV light, which caused haziness and later in color films a bluish hue. A UV filter was used to filtering out shorter ultraviolet wavelengths. Newer photographic film and digital cameras are highly insensitive to UV wavelengths.
UV filters are still used but more as a protection for the lenses’ glass due to their low cost and lack of effect on the exposure of the shot. However, UV filters (in particular filters lacking optical coating) may introduce lens flare and have an adverse impact on contrast and sharpness, especially when a strong light source is present!
A polarizer filter passes light of a specific polarization and blocks waves of other polarizations. The common types of polarizers are linear polarizers and circular polarizers.
CPL or circular polarizing filters are used in photography to reduce oblique reflections from non-metallic surfaces. Polarizing filters can be rotated to maximise or minimise admission of polarised light.
You can use a CPL to increase contrast when taking a photo of the sky, or reduce reflections in glass or on water surface. They are also used to improve the appearance of vegetation.
Polarizing filters also reduce the light passed through to the sensor, depending on how much of the light is polarized at the filter angle selected. Auto-exposure cameras will adjust for this by widening the aperture, lengthening the shutter, and/or increasing the ISO speed of the camera. In case of the Xiaomi Yi, which has a fixed aperture (f 2.8) it will effect shutter and/or ISO.
In photography, a neutral density filter or ND filter, is a filter that reduces or modifies the intensity of all wavelengths or colors of light equally, giving no changes in hue of color rendition. It can be a colorless (clear) or grey filter.
The purpose is to reduce the amount of light entering the lens which allows you to select combinations of aperture, exposure time and sensor sensitivity which would otherwise produce overexposed pictures. Again a short reminder, the aperture of the Xioami Yi’s lens is fixed (f2.8). But you can us the ND filter to force the camera to do longer exposures. There are also modified firmware versions which show pictures with long exposure at night.
Filter for Xiaomi Yi and mounts
There are several filter for Xiaomi Yi with different mounting options. Fixed UV filters which can be put over the lens for protection and mounts with a thread where you can screw the desired filter. I tested two of them a 37mm filter and a 52mm filter:
The Xiaomi Yi has a very wide angled lens (170°), so you have to be careful otherwise you’ll get vignetting (dark edges as the filter extends into the picture) This 37mm filter for Xiaomi Yi shows a bad result in terms of vignetting when lens rectification is turned off. If you turn it on in the App you won’t see any problems:
I wouldn’t recommend using this filter for Xiaomi Yi, as you can only use it with lens rectification.
So I got myself a larger 52mm diameter adapter and filter. In photo mode it still shows some vignetting, but you’re good in video mode. When you switch on lens rectification (lens aberration correction) you won’t have a problem in both modes.
I’m using this adapter when shooting videos, so I’m fine with this one and would recommend the 52mm filter for Xiaomi Yi if you want to use one. I use UV filters to protect the lens. I’ll soon post a video where we were filming with a quad and I wanted to protect the lens from flying gravel. I also use CPL filters when shooting with cars, to get rid of the mirroring in the windshield.
- 52mm Set (with ND filter): 4.91 USD (Gearbest.com)
- 52mm UV filter: 7.61 USD (Gearbest.com)
- 52mm CPL filter: 12.43 USD (Gearbest.com)