Photography Equipment/Lens filters

thumb|A neutral-density (ND) filter Lens filters can be installed in front of your lens. This page will discuss their form factors, describe some popular types, how they work and what to look for when buying. Form factors Round screw-on filters This is the most common type. They have a screw thread that fits into a groove on your lens. You screw them on, simple as that. The filter typically contains a groove of the same size to allow the stacking of multiple lens filters. Their size is measured in millimeters, you have to make sure that the filter you buy matches the groove on your lens. On your lens you will often find an indication like "∅ 58mm", this means you need a 58mm filter. Larger filters can be fitted on smaller lenses with an adapter. The reverse (a smaller filter on a larger lens) is possible but not advised as it will likely result in vignetting. It may work on a zoom lens however, as you may be able to zoom past the vignetting. Many cameras also crop the image when shooting video which may remove some vignetting. If you have multiple lenses with similarly (but not identical) sized lens threads, like a 58mm and a 52mm, you should buy 58mm filters and a 52mm to 58mm adapter. This works for any size, but an 82mm filter on a 37mm lens may be awkward to use. Round magnetic filters Some filters can be snapped on the lens using magnets. They use a magnetic adapter ring that is screwed onto the lens. Unlike screw-on filters, magnetic filters are not standardized. Magnetic filters and adapter rings from various manufacturers may or may not be interoperable. Rectangular slide-in filters These are mostly used in professional productions for color filters and fixed neutral density filters as they can be swapped quickly with little risk of accidentally putting fingerprints on them. Material The very cheapest lens filters could be made of plastic. Do not buy these, buy glass. Not all glass is created equal, but the glass substrate is generally not the limiting factor for image quality. Coatings Lens filters may have various coatings. The type and quality of coating will vary between manufacturers. If you pay less than 10 USD/EUR per filter, you are almost certainly buying uncoated filters. You can use these, but they may induce lens flare and other unwanted reflections. This being said, if you are taking a photo of a car in the sun even a scratched, uncoated CPL filter you found in a garage sale for $3 will vastly improve the final image over no filter at all. The next step is a "multi coated" filter, often indicated by the initialism "MC" on the side of the filter. These are much better generally and start from 15 USD/EUR. Finally there are filters with "multiple resistive coatings", often indicated with the initialism "MRC" on the side of the filter. While uncoated and multi coated filters are sometimes advertised as "anti scratch", this merely means those filters protect your lens from being scratched. A filter with MRC has some resistance to getting scratched itself and is easier to clean. This improves their longevity. They tend to cost a bit more, generally starting from roughly 25 USD/EUR. Some minor scratches or dust or generally not visible in your photos unless you use an extremely small aperture, like f/22. Utilitarian filters UV/protectors While technically different, these are identical in practice. You don't need a UV filter, it will not improve image quality. It will, however, protect your (potentially expensive) lens from fingerprints, sand, dirt, scratches, etc. Think of it like a screen protector on a smartphone. Circular polarization (CPL) Similar to polarized sunglasses, this is a single sheet of polarized glass. It can be rotated inside of the frame to remove polarized light. This can often remove reflections from windows, cars and water, allowing you to see through them. They may also darken the image on LCD and OLED displays. A CPL filter will reduce how much light hits your sensor overall, this is normal. Neutral density (ND) thumb|Long exposure shot resulting in long streaks of headlights thumb|Long exposure shot of the sea, making the water appear like mist Often described as "sunglasses for your camera". In photography they are useful in two cases: if your scene is extremely bright and you are using a lens with a large aperture you might end maxing out your ISO and shutter speed values while still having an overexposed image. This is uncommon, but when it happens an ND-filter is the only solution. More commonly it is used for long-exposure photography, resulting in extreme motion blur. In videography, an exposure time of half the length of the frame display time (e.g. 1/48 of a second for 24 frames per second) is commonly used to make a video more pleasant to watch with some motion blur. If your ISO is already maxed out and you'd rather not decrease the aperture you're out of options and need an ND-filter to get the exposure under control. Fixed ND This is the simplest ND filter. It makes the whole image darker and isn't customizable. This generally results in the highest quality, but is the least convenient. A generally useful set would consist of an 8ND (3 stops), 64ND (6 stops) and 1000ND (9 stops) filter. 3 stops is often used for outdoor videography, 6 stops for outdoor videography on a very sunny day and 9 stops is useful for long-exposure photography. Gradient ND (GND) The same as a fixed ND, but with a gradient in darkness from end to end. Often used to darken the bright sky while allowing more light from the bottom half to reach the lens. Variable ND (VND) This filter consists of two sheets of polarized glass. One of the sheets is fixed while the other can be rotated with a dial. How much light passes through depends on how well the polarization of the two piece of glass aligns. This filter will result in a color shift, how strong this shift will be varies strongly between various brands and models. When designed poorly it may also result in a "cross" effect where the image is darkened unevenly. Do not buy a VND that promises a range of 1-9 stops, the last three stops will likely be unacceptable. You can get the effect of a VND by using two CPL filters if you mount one in the wrong direction (possible using a male-male lens adapter). This isn't recommended. If you don't need to use a lens hood, you should frankly not buy a VND, buy a VND plus CPL instead. That's essentially the same product with an extra dial to control the rotation of both sheets of glass. A VND can be used as a CPL even, by rotating the whole filter within the groove of your lens. This creates a risk of the filter rattling around or even falling out, a problem that is solved by getting a VND plus CPL. VND plus CPL It's the same as a VND, but allows rotation of both sheets of glass independently. They do have one downside: they generally don't fit when using a lens hood. Diopter / Close-up Moves the focus closer. Can be useful for macro photography with a non-macro lens. Will create considerable distortion, though. Stackable. Clear sky (FLD) Fluorescent filter, often sold as a "clear sky" filter for night photography to counter light pollution. May have been useful at one point in time, but has no effect on modern street lighting. Do not buy. Artistic filters Filters that are used exclusively for artistic purposes. Unless indicated otherwise they can be stacked for a stronger or extra effect. Black mist Softens light sources. Makes images look less harsh/clinical while maintaining detail in other areas. Comes in different strengths which aren't really standardized. 1/8 is usually a mild effect, 1/4 is "standard", 1/2 is strong. 1/8 or 1/4 is usually sufficient. Some photographers leave one on their lens permanently. White mist While similar in name, not quite the same effect as black mist. They create a foggy white dream-like haze. Kaleidoscope Creates a kaleidoscope effect. Could be used to create a "dizzy" effect. Blue streak Causes blue streaks of light in one direction to radiate from light sources. May create a "futuristic" vibe. Starburst Causes streaks of light to radiate from light sources, making them look like stars. Color filter As it says on the tin: it just filters colors, so your image looks blue/yellow/green/etc. May be used for artistic purposes, but the effect is easily and more flexibly achieved in post. Stacking the same color will have little effect. Where to buy Used Specialized camera shops Western marketplaces Chinese marketplaces