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The Filters You Need to Own

We rely on post-production so much that optical filters have fallen somewhat out of fashion, but there are still some things that are best done (or can only be done) with the help of a filter.

It’s now so easy to edit photos with software that you may be wondering what the point of traditional optical filters is. It’s certainly true that, for some tasks, filters have been replaced by digital technology that can do a better job.

A good example is the Wratten 85 warming and Wratten 80A cooling filters that were used to correct for lighting of different colour temperatures – we now use white balance adjustments to do this. Or consider the way in which coloured filters were used with black & white film to change the tonal response to different colours – we now do this with Film Simulation modes or by using post-production software. But there are still a handful of things that can’t be done in post-production, and that’s the reason there are still three types of optical filters that are good to have.

The Neutral Density Filter

Eavesdrop on a group of photographers complaining about light and you’d usually hear them say there wasn’t enough of it. Just occasionally, however, the opposite is true: having too much light when you really want to use a slow shutter speed, or a large aperture, is also a problem.

We fix this with a neutral density (ND) filter, which cuts down the amount of light entering your camera. ND filters come in varying strengths, with one-stop, two-stop, and three-stop filters being most common. These are multiple applications for ND filters, such as allowing longer shutter speeds to blur water in landscapes, or wider apertures to blur backgrounds on portraits.

Extra dark seven-stop and ten-stop filters are also available, which can convert a 1/250 sec shutter speed into a 1/2 sec or 4 sec exposure, giving a scene an ethereal, otherworldly look.

The strength of ND filters is quoted as either the number stops of light they reduce, a filter factor, or in terms of optical density. Here’s how these all relate to each other.

The stronger the ND filter you use (or if you choose to stack multiple ND filters together), the more likely you are to get colour shifts in the images you produce. This is for two key reasons: the filters themselves not being neutral, plus infrared contamination due to the length of the exposure. You tend to get what you pay for, so the more expensive dark ND filters are relatively colour neutral, but others are less so, which is why you’ll see some seven- and ten-stop ND filter users working exclusively in black & white. Irrespective of what medium you work in, experimentation is key. Be sure to use the WB SHIFT function on your camera to correct for inherent colour casts.

The ND Grad Filter

The graduated neutral density filter also cuts down the amount of light coming into the camera, but only in part of the frame. The ND effect is graduated so it can be applied just to the top or the bottom of the frame. This is made easier by the fact that graduated NDs are usually ‘drop in’ rectangular filters that use special holders so the grad can be angled, and the cut line moved in the frame to line up with the horizon.

The main use of the grad ND filter is in landscape photography, to even out the difference in brightness between the sky and the foreground. The variance in light levels between these two parts of a scene can sometimes be beyond the exposure latitude of the sensor, making it impossible to get adequate detail in both areas in a single exposure. One solution is to frame multiple exposures of the same scene before merging them together in post-production. But by using a grad ND filter, you can achieve the effect in-camera, reducing the amount of time you have to spend in post-production, and with a single image – useful when you have movement in the frame.

ND grads are available in different strengths and also different hardnesses. A ‘hard’ ND grad has a more defined transition between the dark and light parts of the filter; a ‘soft’ ND grad has a more gradual change.

The Polarising Filter

Landscape photographers have used polarising filters for decades, because of the two effects they can impart on a photo. First, they boost the saturation of things like blue skies and green foliage, making colours seem much richer. While this effect can now be replicated in post-production, the polarising filter’s second quality cannot. Polarisers also reduce reflections in non-metallic materials like windows and water.

There are different types of polarising filter available; the two main types are linear and circular. This doesn’t refer to the physical shape of the polariser (you can buy a circular polariser that’s square-shaped!), but instead explains how the filter polarises light passing through it. Linear polarisers only allow polarised light to pass through in one plane – either vertical or horizontal. Circular polarisers, on the other hand, allow the light to pass through in circles by virtue of a two-part construction.

Which version you need depends on the type of camera you’re using. The general rule of thumb is if the camera you’re using has autofocus, you need a circular polariser.

This is very useful when photographing landscapes that feature water, for example, since wet rocks reflect the sky above them. A polarising filter cuts right through this and lets the detail in the rocks shine through. The filters are also useful when photographing architecture, since they reduce reflections in windows.

The effects of polarising filters are most pronounced when you’re photographing at right angles (90°) to the sun and almost non-existent when you’re photographing straight into the sun or with the sun right behind you. For this reason, using polarising filters with very wide-angle lenses can be a problem, since the effect can vary across the frame.

Your Next Steps

• CHALLENGE Show us what you can do with your polarising filter next time you’re photographing landscapes. It might be in the city or in the countryside. Post your favourite image to social media with the hashtag #learnwithfujifilm and #polarisingfilter. You can also submit your work here for a chance to be featured on our social media channels.