The filters are usually very important in photography accessories, key elements in the shooting and the character of the images.

photography filterWithin digital photography, many of them have become obsolete because they can easily emulated digital post-processing. Within this category fall, to name just a few examples, filters for black and white photography (filters red, yellow, green, etc..) And the filters creative offered by some manufacturers. However, there are many others who until today are just as essential as in analogue photography and can not be replicated digitally more effort made in Photoshop. Precisely for these filters is covered in this article.

UV Filter
Or rather an anti-UV, as it eliminates ultraviolet radiation while maintaining the other values. Ultraviolet light is invisible to the naked eye because they were outside the visible spectrum of light, but some of it is captured by the film causing loss of definition. They are widely used black and white film and color. Digital cameras usually have internal filters are effectively acting in the retention of UV rays. However, we always recommend having one of them placed permanently on the lens for protection against shock, accidental falls or unfavorable weather conditions.

Skylight Filter
Reduces excess blue color, especially in the shadows with a sky or on cloudy days. It also blocks ultraviolet radiation and is often used as a lens protector.

ND filter (neutral density)
The function of these filters, filters also called ‘gray’, is to absorb or block the passage of light to the lens in different degrees (densities) without altering the tone and contrast of the picture. They tend to be useful in different situations:

  • When we work against the light or directly facing strong light sources (sun, snow, etc..) And the combination of lower aperture and fast shutter speeds are not sufficient for a correct exposure of the scene.
  • When we register a movement or panning using low shutter speeds without image burn.
  • When we use large aperture to reduce depth of field (eg. To isolate the subject from the background by blurring) where the speed we want to seal the sensitivity ASA / ISO with which we work or a large light intensity do not allow it to.

In all cases, their effects are difficult (or impossible) to reproduce using digital post-processing. A particular use of this lens you can see from this photo , where I used a ND filter and block for 25 seconds to get to capture the motion of the clouds. By not having a filter they probably would have come out overexposed photo, or the path of the clouds would not be so obvious and would have lost the picture drama. It is also very common to see pictures of rivers in broad daylight with the path of the water blurred, an effect that is obtained using low speeds and an ND filter to avoid burning the photo.

ND filters come with different numbers: ND 2, ND 4, ND 8. The number indicates the brightness points blocks, ie with an ND filter 8 will have to reduce the shutter speed or aperture at 3 points (8 = 2 ^ 3) for the exposure of the picture remains the same and would not use a filter.

Polarizing filter
There are basically two types of polarizers: linear and circular. The first were invented decades ago but with the advent of autofocus cameras have become obsolete, as it usually caused problems in that system. From that developed another type of polarizer, circular, that solves all the above problems.

Polarizing filters are constructed on the basis of two crystals, one fixed and the other rotation. This last feature is what allows us to scale the polarized incidence on the take.

Its effects are often very difficult to emulate with Photoshop: increases the saturation of high tones at the same time decreases the contrast and eliminates reflections from non-metallic (glass, water, snow, polished wood, etc.).. In the landscape can increase the intensity of green vegetation, accentuate the clouds on a blue sky and eliminate smog or fog on the horizon. Justin chromogenic.net demonstrated in a post , so visual and very clear, large differences in certain circumstances, whether to use or not use a polarizer.

IR Filter
Not exactly to block infrared waves, quite the opposite. These filters block all or part of the spectrum of visible light and only let infrared waves, invisible to our eyes. At first glance are completely black. However, a camera mounted on produce images of an almost surreal, with a little help from Photoshop, can be obtained very curious results .

FINAL TIPS
Buy filters in mind their quality, not price. The quality varies depending on the brand and the treatment they have crystals. As for brands, Hoya, B & W and Nikon are the highest quality, but also the most expensive. In a more economical range can be found Tiffen filters, Marumi, etc.. In any case and regardless of the brand, always make sure that the filters are of the type MC (Multi-coated), these treatments have anti-reflection on one or both sides that eliminate or greatly absorb unwanted flashes (the famous flares). The filters without antireflection treatment, besides not absorb stray light, causing loss of contrast, brightness and even loss of sharpness.

Remember you can combine multiple filters, for example screw a polarizer on a ND and then fixed to the camera. But keep in mind that more than two filters used at once, can produce adverse effects in the image.

If you are users of DSLR cameras and lenses have several different front thread sizes, buy filters to the maximum extent and in any event thread then use adapter rings (gearboxes, in this case) for minor measures. If there are digital camera users point-and-shoot or prosumer range (Sony F828, Nikon Coolpix 8800 et al), make sure that in fact the lens front thread possesses universal, and if so, find its diameter to know what As filter to buy.

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