Taking Control of Variables

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Taking Control of the Variables

I love shooting long exposures. I find there’s something

Kieran Metcalfe describes the

freeing in not quite knowing how the shot will turn out.

benefits of shooting with a

You’ve found a great vista with the clouds blowing towards

Formatt Hitech Variable ND Filter

you, or a perfect waterfall where the white foam will form streaks to draw the viewer in - but you still don’t know the exact shapes either of these will paint on the picture.

There’s something which engages my creativity, knowing I can only control the general composition, and that the overall success or failure will be governed by the random movement of the water, clouds, traffic, people…

When I started out, I was drawn to extremely long exposures, where water turns to milk and creates a soft, ethereal scene.

As such, I jumped straight in and bought Firecrest 6- and 10stop NDs. They’ve served me really well, and I do still enjoy the results I get with them.

But lately I’m finding that in some shots – especially flowing water - I’d like just a hint of texture to convey movement.

Smoothing the water too much, while creating a peaceful effect, can soften the life out of the scene. Equally, too short an exposure will leave the image busy and harsh.

So, limited by the exposure triangle and the equipment I had in my bag, my approach was to take both images and blend them in photoshop, overlaying the sharper foreground to bring a certain amount of detail back into the smooth water.

Don’t misunderstand me - the resulting image is one of my autumnal favourites, and I am more than happy with the reception it got - shortlisted in Outdoor Photographer of the Year 2018, and chosen as Digital Image of the Year at our local club. However, there’s still something which annoys me about the amount of work it took to create. I’m not averse to a bit of post-production, but it still feels like more work than you should need to do!

A simple solution would be to buy a few more filters – starting with a 3- or 4-Stop, and perhaps a 1- or 2-Stop. But that’s a lot of glass to be carting around to allow for different lighting conditions on different days – and expensive too.

The Variable ND solution When I heard that Formatt Hitech had brought out a Variable ND Filter, my interest was piqued. Although originally aimed at videographers, I could see how it might apply to the situation I

An example with fixed NDs

was finding myself in.

That said, I did have my concerns. Variable NDs get a lot

This is an image taken a couple of years ago in Padley Gorge,

of bad press, and indeed my first foray into filters was with

one of the jewels of the Peak District. After a morning hunting

another brand’s product. It was bought for me as a gift, so I

for a scene just like this one, I had given up and was making

must be tactful here, but let’s just say it wasn’t great.

my way back to the car. A final detour along the river and I found what I was looking for and set up for the shot.

It suffered from some downfalls, as cheaper products often do. I was lucky that it was largely free of colour-cast under

The problem I faced was one of not having the right filters for

moderate use, but did go a little purple when dialled up to the

the job. The tree was in a relatively shaded location and my

max. Crucially though, anything more than a minor adjustment

least-strong filter was a Firecrest 6 Stop ND, which was totally

resulted in uneven dark patches appearing on the image.

blurring the water at 30 seconds. An unfiltered shot came in at 0.4sec and was far too crisp as it was a fairly wide view.

This is down to the way these filters operate. They are essentially two circular polarisers, one fixed in place, and the other allowed to rotate in front.

If you are not aware of how a polariser works, imagine it as a row of bars with gaps between. On the basis that light waves oscillate as they travel, when they reach the ‘bars’ of the polariser, only light which oscillates in line with the gaps can pass through.

Too smooth at 30sec

Too crisp at 0.4sec

Could I have been more flexible with the camera settings and increased the shutter speed naturally? Of course that’s always an option, but the nature of the exposure triangle is that any change in one variable alters one aspect of the image or another.

I was already shooting at ISO 100, so reducing the sensitivity to lengthen the shot wasn’t an option. I could have dialled the aperture down, but on my crop sensor, getting past f/16 starts to soften the image.

Cheap filter causing uneven darkening of the image

When you stack two polarisers to make a Variable ND Filter,

Absorption at approximately 1, 3 and 6 Stops

you add a second set of bars. If one is rotated so that the two sets of bars are not aligned, even fewer light waves can find a way through, creating the ND effect.

However, on cheaper Variable NDs, this can create uneven patches on the image where the effect is stronger in some areas than others. My direct experience of this issue left me initially wary of the Formatt Hitech offering.

However, the higher quality product they have produced means that this effect is pretty much non-existent. Part of

UV

Visible Light

IR

the solution is that the maximum strength of the filter is

to the live-view histogram, precisely limit the light levels for

limited to around 6 stops, while others claim to go as high as

the correct exposure. Even if I had a Full ND from the weaker

10 Stops. Credit is due to Formatt Hitech for acknowledging

end of the range, and one which was ‘near enough’ what I

the limitations of the technology, rather than marketing an

needed, it would not have given the same level of control as

unusable filter which can ‘technically’ achieve a stronger

the Variable ND.

effect.

The other advantage is that the Formatt Hitech Variable ND

Of course, the higher quality of polariser and glass also helps.

has a rear ring which allows you to lock the orientation of

As well as a reducing the ill-effects of poor polarisation,

back polariser, so it can perform the role of a normal CPL. I

Formatt Hitech have worked hard to ensure minimal colour

set it at an angle which cut out the glare from the wet rocks.

cast from the glass. Due to the limitations of polarising

The front polariser then rotates to apply the ND effect. This

technology, there is an unavoidable but very slight warming

feature makes it somewhat equivalent to using the Firecrest

tone to the filter. However, shooting on AWB (or manually

holder with its built-in polariser.

adjusting after mounting the filter) easily allows for the camera to compensate for that. They’re indicating this clearly in the name by not ascribing it the Firecrest moniker.

Reassured, I thought that it was worth considering as a way to provide some flexibility when shooting “short” long exposures - and I was impressed with the results..

Putting it to the test I first tested the filter on a visit to Waterfall Swallet in the Derbyshire Dales, located in a deep sinkhole surrounded by trees. I had been before during the summer, with the leaves providing cover from the bright sunlight, but this second trip was in winter, and the bare trees gave no shade. The falls were in partial light meaning there was far too much contrast for a shot of the wider scene.

I searched for more intimate compositions and not wanting to re-shoot a close-up of the face of the falls, I decided to work with a clump of ferns hanging from a mossy rock - the vibrant greens contrasting with the greys of the waterfall behind.

However, a shot at my usual f/11 contained too much detail throughout, looking flat and busy.

This called for a wider aperture, f/5 in this case, to provide separation by throwing the waterfall out of focus. As my ISO was already at 100, a slower shutter speed was needed to compensate. Using a filter was the only option in order to get back to the third of a second exposure I needed The beauty of working with a Variable ND in this setting was that I could set the camera exactly as I needed and, referring

The filter’s rear locking‑ring allows the polarisation to be set as required.

1/13sec

0.3sec

Flexibility to experiment

Squaring the Exposure Triangle

I was also able to make good use of the Variable ND on a

With a decent variable ND at your disposal, you can exercise

shoot at the iconic Etive Mòr waterfall. Heavy snow and

even more creative control over your images. You keep the

storms had significantly swollen the River Coupall and it was

wonderful uncertainty around the specific tracks and shapes

raging over the falls. That much water with a 6-stop ND would

the water will make - that creative partnership with the scene

have been a white mist with no detail at all.

itself – but you gain greater control over exactly how you

Filterless, the shots were coming in at 1/60sec – far too short for a pleasing image – but the Variable ND allowed for just the

capture it. Choose your aperture, ISO and shutter speed - lock them in, and fine-tune the light levels to suit.

right range of shutter speeds. The simplicity of being able to

In one sense, I think of it as turning the exposure triangle

vary the exposure easily, without swapping filters, meant that

into a square. Of course, any ND filter will do that, but not

I could quickly experiment with different versions of the same

with the degree of control a Variable ND can offer. This gives

composition.

an immediate flexibility which is useful if the light changes

The only problem this has left me is the struggle to decide which of these two I prefer!

Some scenes and styles will undoubtedly need a strong 6-, 10-

Again, the polarising aspect of the rear filter was important here as it accentuated the jade green of the water by limiting reflections on the surface.

slightly while you’re working on the image.

or even 16-Stop ND for the desired result but, especially when shooting flowing water, the Formatt Hitech Variable ND is now a go-to item in my photography toolkit.

Kieran works freelance as a Graphic & Web Designer, and describes landscape photography as a chance to be creative for his own brief. He was the winner of the Campaign for National Parks’ 70th Anniversary photography competition and is often to be found photographing the Peak District.

Find him online at facebook.com/kieranmetcalfephotography instagram.com/kieranmetcalfe and kieranmetcalfephotography.co.uk

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