Filters come in various shapes and sizes and for different purposes. Not everyone ever needs filters, especially as some of their effects can be replicated in post-processing. However, in some situations filters are the only way to achieve desired results. They are popular especially among landscape photographers and videographers.
If we forget all effects filters, there are three types of filters you may want to use: neutral density (ND) filters, polarising filters, and UV/protective filters. While UV filters may have some very minor image-enhancing features, they are mostly used for protecting front lens. Polarising (typically circular polarisers) filters are quite popular among landscape photographers as they make blue sky darker and more saturated and affect reflections on water, for example.
Out of these basic filter types ND filters offer the most creative possibilities. First of all, these can be divided into normal even ND filters and graduated or reverse graduated ND filters. As the name suggests, these filters should be neutral and their only purpose is to block some light coming through without affecting the image otherwise. The reasons you may want to do that are:
- Fast lenses and very bright conditions. For example, many (slightly older) Olympus mirrorless cameras have a maximum shutter speed of 1/4000 s. If you combine this with f/1.8 or faster lens and sunny weather, your photos are likely to be over-exposed even with the fastest shutter speed. To restrict the light coming in, use ND4 (2 stops) or ND8 (3 stops) filter.
- Videos. You may want to control aperture and shutter speed independently for the desired look, in which case you probably need a good set of different ND filters or a variable ND filter.
- Long exposures. This is my cup of tea. I have got interested in long exposure photography and in order to do that in daylight you need extreme ND filters such as ND1000 (10 stops). Silky smooth water is the most used effect of long exposure.
- Bright sky in comparison to dimmer ground can be balanced with graduated or reverse-graduated ND filter.
Circular threaded or square filters?
Circular threaded filters are more common to at least hobby photographers. They come in different sizes which is chosen based on the filter thread of your lens. Larger filters can be used on smaller lenses with the help of step-up rings.
Advantage of circular filters is that they are more straightforward to use. They also take less space and are cheaper if only one or two filters are required.
On negative side, you basically need various sizes for different lenses, although step-up rings can be used. Threaded filters also become cumbersome if more than one filter is to be used at once. Stacked filters typically cause vignetting and they may get stuck together causing troubles to separate them without tools. Use of graduated threaded filters is also quite limited as you cannot move the transition line.
Possible issues with filters
As with filters you add something in front of your lens, some issues may arise:
- Vignetting. Filters on wide-angle lenses easily cause vignetting. To some extent it can be avoided by using only one filter at a time and slim models (circular filters) or large enough filter size (square filters). However, with ultra-wide angles vignetting cannot be avoided.
- Reflections, ghosts, and other optical issues. High price does not guarantee trouble-free results but cheaper filters tend to have more problems. When you put cheap glass, or resin as many cheap filters are made of, in front of your expensive nano-coated lens, things may not work out perfectly.
- Colour cast. This is a common problem with cheap and even a bit more pricey filters, especially high-stop ND filters. In long exposure even slight colour cast (often magenta) can end up as huge colour shift. Slight shifts can be corrected in post-processing but it may deteriorate colour reproduction.
The photo below suffers from significant magenta cast and those odd reflections – a ghost reflection of sun can be seen below it. Especially the reflections are bad as they are basically impossible to correct in post-processing. I will try to investigate them a bit more at a later time. I know that these tend to appear with square filter system if the filters are not exactly parallel to the lens surface and when there is very bright light source.
Even if the magenta cast is corrected by white balance tool, the colour reproduction still seems slightly washed out and dull.
My filter kit
I have a mixture of square and threaded filters. My “main” landscape filter kit is built around Formatt-Hitech 85mm square filter holder. I have several adapter rings for different lens thread sizes but currently I mainly use it with Olympus 12-100 Pro lens (used with 12-40 Pro before it was replaced by the 12-100).
85mm square set:
- Formatt-Hitech 85mm filter holder
- Kood ND8
- Haida ND1000
- Formatt-Hitech Graduated ND8
- Formatt-Hitech Reverse graduated ND8
All of these filters are so called budget models. Haida ND1000 is the only glass filter, the rest I assume are resin. Haida is also the best of these without visible colour cast. Kood and Graduated filters are ok as well. I used to have Formatt-Hitech ND16 resin filter but it had very bad magenta cast, that one has been used on the photo above. Therefore, buying these cheaper end filters is a bit of a hit or miss.
If you want to go for the safe choice, Lee filters have good reputation but also cost a lot.
Circular threaded filters
- 72mm Hoya Pro1 Digital circular polariser
- 72mm Olympus protective filter
- 46mm Haida ND1000
- 46mm Hoya filter set with UV protective filter, ND8 and circular polariser
- 37mm Hoya ND8
72mm circular polariser is what I use on Olympus 12-100 with the square filter kit if I need. After good experience with Haida ND1000 square filter I also bought 46mm ND1000 filter for some travel use. Olympus 17/1.8 and 25/1.8 (and also 12/2 I do not have) use 46mm filters.
I have not used protective filters with Micro Four Thirds lenses before but I do have one on the Olympus 12-100 simply as it is an expensive lens and have rather large glass surface. Typically I use lens hoods as mechanical protection for lenses.
In threaded filters Hoya is a big name; they have several product ranges from budget filters to more expensive special-coated models. B&W are well known but tend to cost more as well.
Here are some example photos what can be achieved by pushing exposure time a bit longer.
North Berwick. F/8, 2 seconds.
Edinburgh. F6.3, 8 seconds.
Pitlochry. F/8, 0.5 seconds.
Liverpool Street Station, London. F/14, 0.8 seconds.
Edinburgh christmas market. F/8, 0.5 seconds.
In fact, only the four first photos are taken with ND filters and tripod. The last three are actually without filters and handheld – thanks to Olympus’ great image stabiliser. However, all show the effect of longer exposure – sometimes you can do it without filters and tripod as even half a second exposure time may be enough to get the effect.