Effect filters allow us to alter the images we take, an example would be a star filter that adds small stars in an image to any highlight, such as crests or waves or chrome work on vehicles.
There are quite a wide range of effect filters, and the way they work is often altered to a degree by the aperture and lens that you use them with. Some work better in some situations than others and some may come under the 'experimental' label, in that you are unsure when you take an image if the result will be good or not. An example would be a filter that adds a simulated motion blur to an image allowing you to make it appear that something is moving very fast, or another might be a filter that adds a rainbow to a scene.
I have not included in this article the ND filters or ND or colour grads, polarizer etc that are in more common use, these are covered in separate articles within the Filter Section . There is also a more general introductory article to filters that introduces some of these see :-
Close focusing filters
These supplementary filters or lenses fit to the front of any lens to allow it to focus far nearer than normal. They come in different strengths and you can combine two or more together to create other strengths. Lenses can usually auto focus but only now within a very restricted range. The difference in results between a good and bad one of these is very noticeable. You will also find they work far better with some lenses than others.
Generally a macro lens will produce a far better result and is able to focus over a far wider range. Tubes (spacers between camera and lens) also allows lenses to focus closer but for many lenses you need a very thin one, a macro lens on the other hand will produce excellent results with a number of tubes together and more.
Split focus filter
Used to allow something in the near area at the bottom of the image to be in focus while the distant items as areas well, they can be effective but positioning may be critical.
Star and similar filters
These come in a variety of designs, both as screw-ons and for filter systems, some for filter systems are only partial coverage. A typical one is the round star filter with 6 or 8 points, if you look at this you find its a clear filter with fine engraved grid lines, and its the light catching the joints in the grid that creates the stars, the number of directions the lines go in altering from one to another to produce different numbers of points. You can use it in scenic shots, for product photography, and its particularly effective when taking street shots at night, or of Christmas tree lights. I carry one, but use it only occasionally.
Varicross is similar, it has two glass sheets each engraved and you can rotate them, so for example having a 4 star or all going in a single direction.
A variety of designs similar to the star effect in use but produces either a variety of colours on star lines or a circle of lines a little out from the light source.
Adds a simulated rainbow, but I have not seen one that appears real, also with a real rainbow the brightness inside and out are different.
Soft filters, netting filters and the like
Designed to produce a softer rather than out of focus image. Used by some for portraiture of ladies where the sharpness of the lines of experience and skin texture may want to be camouflaged. Results similar to a poor lens. You may be able to stretch tights or even clingfilm over the lens to get a similar effect. The effect can also be produced in editing. Most of us however are looking for sharp rather than soft images. Soft filters etc come in both screw-on round filters and filters for filter systems. I have one, it came as a part of a larger kit of lenses, but I never use it, except occasionally when teaching and someone wants to use the effect.
Multi image filters
Usually screw on but can also come for filter systems. This is the 'top of the pops' type images where you get a main image surrounded by a number of smaller versions, more effective when used with video than for still work. When you first have one its fun but you quickly tire of the effect, so look on the second-hand market if want one.
Motion blur and similar
These filters have ridges or similar on an area of the filter and when you use them that area is smudged or produces multiple images, so the positioning of this is critical. If you get it just right it can look effective with a simulated motion blur behind something moving fast.
Clear centre and outside effects
There are a variety of filters that have a clear centre that displays the central part of the image normally and then corrupts the outer part of the image, perhaps adding swirl effect, a colour or softening or fading the image.
Simulated mist or rain on part of or all of the image area. This can also be simulated by putting something fine like cotton in front of the lens across a part of the image area.
Mirage, and reflection effects.
In effect reflecting a part of the image so as to make it appear that there is a lake or similar reflecting the upper part of the image.
Keyhole like effects
Pre shaped cut outs that make it appear you are looking through a keyhole or other shape - more fun to make your own.
Light balancing filters
Were used with film to, for example daylight film with electric lights, with white balance on digitals technically we don't need it. Light balancing filters for your flash however may be helpful in that it allows your flash to mix with other lights, and you can then turn your white balance to match the prevailing lighting, getting over mixed lighting problems.
Half colour, dual colour, tri colour and fantasy sets
Filters that produce usually very striking unnatural effects. May appeal more to you if you are using them than others who you show your work to. There are also filters that rotate against each other, producing a range of combined effects.
There is a filter that combines a polarizer with two coloured grads, each rotating separately, now what would that produce, and is it worth the expense to find out.
Few, if any of the filters on this page will be widely used by you, unless you are an art student or have a specific other interest in less conventional photography. The star filter is the only one I would suggest you may like to play with at some time.
For the commercial photographer used sparingly, they may add a special effect for an advertising photo or similar.
Its therefore far from essential items to add to your armoury, and perhaps if you have a few you won't carry them as you will have other items that need the space in your camera bag.
However they are a bit of fun, and perhaps can be used to entice others to play with photography and filters.
But before you rush out and buy some to play with take a look at the other, more useful, options in the Filter Section page.
See also: Filter Section for more articles.