For professionals, filters are essential tools which will be taken to each and every shoot they undertake. In the past, before the digital era, filters were used as one of the photographers primary creative tools and with the introduction of digital photography, it could have easily been perceived that post processing would take over that dominance for creative manipulation of photographs. In reality, filters are still as popular as ever, because they offer the photographer means for creativity in-camera that cannot be as effectively replicated in post processing.
When using filters, you are manipulating the intensity and the colour within that light to gain an effect upon your final image and you therefore record the shot with that added effect. Remember, there isn’t any option to remove it afterwards, so it’s essential to understand what filters best suit the work that you do and how you can used them effectively.
Photo by Kain Kalju
Square or Circular?
There are two common filter formats, circular filters screw or clip on to the front of the lens of your camera and are extremely practical and portable. They come in a whole range of sizes in order to fit the huge variety of lenses available. As we mentioned in part one, check your sizes!
The other type come in the form of square or oblong glass plates that slide into an adaptor which you are able to screw onto the front of your lens. This system gives you greater flexibility when using filters that have a gradient as you are able to adjust the height of the glass in relation to the lens and therefore use as much or as little of the filter gradient as you desire. These adapters also rotate, which is good for polarizers.
A square system, like the Cokin system, also is more cost effective for using filters on different size lenses. If you have a lens with a 52mm thread mount and a different lens with a 72mm thread mount, you can just buy both of those mounting adapters and use the same physical filters and filter holder.
Photo by mbiskoping
The most common type of filter is a UV filter, which appears to look like clear glass, but actually works to reduce the amount of ultraviolet light passing through the lens, as it can cause haziness when film and camera sensors are exposed to it.
The filter still lets through the light compromised of the visual spectrum, but blocks out ultraviolet radiation. However, many photographers use a UV filter primarily as protection for their lens because it doesn't typically reduce the light entering the lens and the UV filtering isn't a drastic effect. It can also be useful to protect the lens when working in sandy or dusty locations.
One of the only negative elements to using a UV filter is that some cheaper filters aren’t made to have perfectly flat surfaces, which can distort images and cause unwanted reflections.
Photo by Dave M
More About Neutral Density Filters
We mentioned this in the part of the series, but we want to talk about more uses and a couple special types of ND filter here as well.
Let's say you wanted to take shot of a city skyline and extend the shutter speed to accentuate the lights, you could use an ND filter to block out lots of the light in order to decrease the shutter speed to the appropriate length.
They are also useful if you want to make long exposure images during the day. Even at ISO 100 and f/22, an exposure on a bright day might still require a shutter speed of 1/60. If you want to make a 3 second exposure to show motion blur or something even longer to make all moving objects disappear, you'll need an ND filter.
It's also important to not that there are different grades of ND filters according to their "filter optical density" and therefore how much light you want to block out. There are a wide variety available to buy, but the most common are ND2, ND4 and ND8, which works out as 0.3, 0.6 and 0.9 according to their filter optical density or 1, 2 and 3 stops according to f/stop reduction.
Graduated Neutral Density Filters
Where graduated neutral density filters vary, is that through the filter, the darkness varies, typically starting clear at one end, then shading through to a higher density at the opposing end. Basically, one side of the filter is darker than the other.
Photo by Jez B
This could be used, for example, in a situation where a the exposure settings required for a bright sky vary greatly from those required for the corresponding foreground. The higher density end of the filter could block light from the sky, leaving the clear end to allow light into the lens from the foreground.
Photo by Carl Jones
Variable Neutral Density Filters
We mentioned earlier that ND filters come in different strengths or densities. Obviously, buying one filter that changed densities would be more convenient. Well, you're in luck. They are typically pricey, but there are several brands of variable ND filters that sport a ring which allows you to change the density.
These are commonly used by photographers shooting in black and white to adjust the contrast within a shot, for example, a green filter used for a landscape shot would darken the sky but enhance the vibrance of any green foliage within the shot. A yellow filter will provide a boost in contrast and a red filter will offer even more dramatic contrast results.
Using these filters when shooting color will just change the color of the image, but they can be used to correct white balance. They were used to do just that when people shot slide film.
Photo by Nadar
A diffusion filter is designed to give the shot a soft and fuzzy feel and makes the image look dream like. It also reduces the contrast within the shot. This affect was very popular for portraits in 60s up through the 80s, but is less prominent now. You can even buy them with a center that is not diffused, giving you a sharp face.
Photo by RIDG
Skylight Filters are often used in a similar way to UV filters, as a means of protection for the lens as it doesn’t provide any dramatic optical benefits, although when used outdoors, it does reduce the blue tint that you sometimes get on a bright day beneath a big blue sky. They also reduce reflections from affecting skin tone.
Warm Up Filters
Warm up filters enhance your shot by doing pretty much as they say on tin, by adding a presence of warmth to a shot (see example below). They slightly changing the colour temperature, which can be particularly useful when working with certain light sources. They are also very useful for boosting skin tones and like ND filters, you can also get them in graduated formats. They are basically an orange colored filter.
Photo by Hantslad
Fluorescent filters are useful for compensating and adjusting the light given off by fluorescent lighting, mainly reducing the green/yellow tint, although this can also be compensated for by using white balance adjustments. Like the warm up filters, these are basically custom colored filters made with color correction in mind.
Speed filters offer a very specific feature, in that they add streaks of light, creating the look of motion blur that gives the impression of speed. These were pretty gimmicky when they were invented, and remain so now, but that doesn't make them any less fun to play with.
Photo by mbiskoping
There are also a whole host of other creative filters available, that have been written about in detail here: Star, Fog, Centre Spot & Day for Night Filters and here: Multivision, Close up, Sepia, Infrared Filters
If these articles haven't made you interested in using filters, we don't know what will. Filters have been around for a very long time. Understanding filters not only gives you a glimpse into how people did things before digital post-processing was available, they also give you a better understanding of how light works. We hoped you enjoyed this series. And, if we left out any cool filters tips, please fill us in by posting a comment!