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BOOKS AND ARTICLES Filters, hoods and lens care
The filter is a device that, in the most common version, is screwed in front of the front lens of the lens and is used to obtain a variety of effects or to delay either a certain range of light waves (color, ultraviolet), or to proportionally reduce transmitted light (ND - neutral density) , or to exclude light waves of a certain polarization (polarization).
In addition to the threaded filters mentioned, there are also less common "gelatin filters" made in sheets. It is necessary to cut the desired size and place it in a special holder in front of the lens. Basically these filters are used in situations where filtering of a certain color is needed. They are distinguished by very little wear resistance and very accurate color matching. There is an option covered with a layer of plastic - laminated filters, they are more expensive, but more durable. There are also filters made of special organic glass, which are more durable than gelatin and have good optical characteristics. The most famous filters are Cokin. The main parameter of the most common threaded filter, in addition to, of course, its properties and purpose, is the thread diameter. To select a filter for your camera, specify the diameter of the thread on the lens. It is usually indicated either on the lens itself or on the protective cap. If necessary, you can also use adapter rings for filters with different diameters. For example, a filter with a diameter of 58 can be put on lenses with a thread diameter of 55, 52 or 49 using an adapter. Pros and cons of using the most common filters - protective, UV and SKY There are two main views on filters among amateurs and professionals. Unfortunately, mutually exclusive. The first of these is that filters are useful, it is recommended to always wear a filter (protective, either ultraviolet or SKY) on the lens to protect the lens from scratches, damage and to filter out UV radiation invisible to the eye, usually not at all useful for the image, as well as to give natural " warm tones frame. The second is that filters are harmful, no protection provided by a filter can compare with the deterioration in image quality caused by extra elements in the lens, two additional reflective surfaces. In general, lenses are designed in such a way that they shoot well without any filters. The literature does not provide unambiguous advice. Nobody is engaged in practical verification of these disagreements either, because the interest is mainly in the dispute. Apparently, the first option with reservations can be considered the most correct. All the stories about the deterioration of the picture quality due to additional "interference" in the optical system mainly refer to the days of the past, when there were no available technologies for complex coating of glasses, and to modern cheap crafts that are made of not the best glass with bubbles and often do not have enlightenment or have one-sided enlightenment, and even that is of poor quality, which is easily destroyed. At the same time, supporters of a second opinion are often guided by advice expressed almost in pre-war literature or in domestic sources, which were guided by the same domestic level of quality and technology for manufacturing filters and optics. It should also be mentioned that what was considered impossible in optics 10-20 years ago is now commonplace. When choosing a filter, you should trust the products of B + W, Tiffen, Hoya, branded filters such as Canon, Pentax, Nikon or Minolta. When choosing a filter, it’s also a good idea to make sure that you don’t have a fake in front of you. It rarely happens, but it's worth mentioning. This is quite difficult, but in such cases it is worth shopping in stores that have a large range of filters. The only filter, even in a beautiful box, but which has an unknown name is better not to buy. You also need to pay attention to packaging, accuracy of manufacture and other external signs, such as the correct spelling of the company name. A filter, especially an ultraviolet or polarizing filter, should preferably have a multilayer coating, which is often called MC - MultiCoating. In general, a good "trusted" filter does not degrade image quality enough to be noticed at all. Therefore, I recommend to all amateurs (the pros themselves will figure out what's what) along with the camera to purchase a filter - UV or SKY. And the protective filter has a lot of positive sides. And in most cases, when shooting amateurs, they outweigh the supposed negative sides. First of all, it is the mechanical protection of the lens. In this case, a filter - a piece of glass worth 20-50 dollars can practically "save" the camera lens, which is 10-20-30 times more expensive than it. In addition, the filter can be wiped without fear of damaging the lens, it protects the lens itself from dirt, dust and water splashes. This has a serious plus, since without a filter to ensure protection against dust - splashes, the lens has to be covered all the time with a cap. What efficiency does not add. It also makes sense to use a UV or SKY filter as a permanently worn and protective filter due to the fact that such filters eliminate the color balance shifting to blue when shooting in bright sunlight and in other situations. The human eye, unlike the film, is not sensitive to the UV part of the radiation and does not see this blue. By blocking UV radiation, filters remove excess cold blue colors from the frame. Then do not forget that the filter can always be removed. The missing filter is difficult to put on. Main types of filters There are a very large number of filters, let's focus on the most common and often necessary. Almost colorless UV filters (HAZE) or slightly pinkish SKY filters are used to filter out parasitic ultraviolet radiation. Depending on the type, these filters reduce or completely block UV radiation and add warm colors to the frame. Polarizing filters It is often difficult to achieve good quality when shooting through glass or a correct exposure when sunlight is reflected from water or other surfaces in the frame. Reflected light is different from ordinary light. The light that illuminates the subject - unpolarized, at the same time reflected light, such as reflection from non-metallic surfaces, has a pronounced polarization. A polarizing filter is able to block light of a certain polarization. By rotating the filter, selecting the plane of polarization, you can eliminate or seriously reduce parasitic reflections on surfaces in the frame. By looking into the camera's viewfinder and rotating the filter, you can see the result. The polarizing filter is the only filter (other than gradients) that can darken the sky without affecting other colors in the frame. Neutral density filters - ND These filters are designed to proportionally reduce the amount of light. They are used, as a rule, in cases where the camera, say, does not "enough" the minimum shutter speed or there is a need to use a slow shutter speed. This situation can occur, for example, in bright light. The main parameter of the ND filter is the density, that is, how much of the light the filter retains. The designations 2X, 4X, say, say that the filter transmits 50% and 25% of the light, respectively. Another way to indicate densities is with numbers from 0.1 to 4. A "0.3" filter, say, reduces the amount of light by 2 times, and "0.6" by 4 times. There are also filters with non-constant density - gradient, part of the filter is darkened, and part is not. Such filters can be useful, say, when shooting landscapes, in most cases the horizon line divides the frame "in half" - by setting the darkened part of the filter on top, you can darken the sky without affecting the light intensity of the rest of the frame. Effect filters They are used to obtain a variety of effects, such as multi-beam stars around light sources or to add a romantic haze to a portrait. Often the filters are completed with a tiny booklet that describes the filters of this company. The main types of filters have common names from different companies, and a filter, say, 81A, is available from both B + W and Hoya. PRO-MIST and Black PRO MIST Create a blur effect (soft focus). PRO-MIST filters change the image in 3 ways. First of all, they smooth out excessive sharpness without causing an out-of-focus effect. Numerous light sources acquire a slight aura. The filter also slightly reduces the contrast, brightening the shadows. BLACK PRO-MIST is more softened than PRO MIST of the same density. The filter also reduces contrast, brightening the shadows and darkening the light parts of the frame. Filters are available in densities: 1/8, 1/4, 1/2, 1, 2, 3, 4 and 5. SEPIA Adds a warm brown tint to a color image, allowing for an artistic "old" photo effect:
Center - Spot The filter gives the effect of a clear center of the frame with blurry edges. It is a diffusion filter with an optically clear circle in the center. It is used, as a rule, for portraits and to highlight the main subject in the frame. Fog FILTERS This type of filter creates soft halos around light sources such as lamps and window light. Using these filters, you bring a mystical fog into the frame, at the same time the filter slightly reduces contrast and sharpness for a stronger effect of scattering in the atmosphere. The filter comes in different effect densities. Blends They are used to cut off side rays of light that do not participate in the image creation process, but only introduce interference and stray light. The hood is attached to the lens with a thread, like a filter, or with a special bayonet mount. There are also lenses with built-in rubber hoods. In the case of a bayonet mount, a "branded" hood is needed, which does not exclude, of course, the use of a hood that is attached to the thread. The main parameters of the lens hood are the diameter of the mounting thread (as with the filter) and the focal length for which this lens hood is designed. Using a lens hood designed for a 50mm lens on a 35mm lens or on a zoom lens such as 28-105 will cause a noticeable darkening of the corners of the frame (vignetting) at focal lengths less than 50mm, especially noticeable at the minimum focal length, because the lens hood will "cut off" part light rays involved in creating an image. It will also be visible in the camera's viewfinder. For a zoom lens, you need to select a lens hood recommended by the manufacturer or suitable for the thread diameter and designed for the minimum focal length of the lens. For example, for a 35-105 lens with a 55mm filter thread diameter, a lens hood with a 55mm thread diameter and designed for a 35mm or 28mm lens is required. A lens hood can significantly improve the image in some cases, especially when a strong light source is in the frame or direct sunlight hits the lens. Or the lens does not have high-quality blackening of internal surfaces. In addition, the hood provides mechanical protection for the lens. Optics Care Sooner or later, almost all video enthusiasts face the need to clean the lens. Filters are usually used to protect the front lens of the objective from contamination. If all the same, dust has got on the lens, it must be blown off with air. It is advisable to use a special air pear from the optics cleaning kit or a banal clean enema. Do not blow dust off with your own lungs. Dust may disappear, but saliva stains will appear. Instead of an enema, you can also use a special compressed gas to clean photographic equipment. If the optics are heavily soiled, such as fingerprints or dirt, it is necessary to prepare for the cleaning procedure more thoroughly. As a liquid for cleaning optics, it is necessary to use only specialized means for cleaning photographic lenses, which are a mixture of pure alcohol and ether. Alcohol-containing surrogates cannot be used - after cleaning, a hard-to-remove plaque will remain, which is not at all easy to clean. Special non-abrasive non-fiber cloths or special grades of ultra-thin rice paper are also used as optics cleaning material. In any case, the general advice is to use only those products that are intended specifically for cleaning photo optics. Special kits for cleaning optics are sold in photo stores. A variety of glass cleaners or glasses are strictly not recommended. First of all, you need to blow off everything possible with an air bulb, then try to gently breathe on the lens until it fogs up. Gently moving the special cloth in a circular motion from the center of the lens to the edges, without any serious pressure on the lens, try to remove the dirt or imprint. It is important not to be nervous and not to apply force. You may need to repeat the process several times. If necessary, apply special fluid. The lens cleaning cloth is lightly moistened and the procedure described in the previous paragraph is carried out. Never pour liquid directly onto the lens. It can get inside the optical system, seep between the lenses and the lens will be practically lost. In case of clinical cases of contamination, if dust and dirt get inside the lens, it is necessary to resort to the services of a workshop. Based on an article by Oleg Belkin
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