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Alex Hare Photography

Neutral Density Filters-what’s their role in digital photography?
Landscape &Travel Photography Techniques

Apr 10th 2012

If you want to jump straight in and watch a short video of a dawn shoot unfolding on the Cornish coast where I discuss the use of ND filters click here.

These filters are super popular: Lee, the market leader, are sold out until late 2012 and have been for some time.  Prices too have rocketed.  So what are they and why are they so useful in our photography?

Also, how come, if we’re all living in a digital utopia, we even need these pricey bits of plastic when we can simply merge different exposures in Photoshop?   To get the dynamic range-the range of brightness in a photos shadow areas and bright bits- surely we just need to take one shot for the dark foreground and one for the gorgeous bright sky, blend them in Photoshop and we’re done.  Why bother with these filters at all?  Well, I’ll come to all that later, first lets look at what these filters are.

Postling, Kent.  This scene is perfect for a ND grad-dead level horizon and a simple case of holding back the brighter sky so it stays blue when I expose for the slightly darker foreground.   You can't tell it's there ansd that's the idea behind good use of filtration-it looks natural.  Nikon D200, 17-50mm, 1/15 sec, f11 ISO 100.

ND filters are like a pair of shades for your camera; they are dark and let less light in.  The Neutral Density one (ND’s) are all dark allowing less light in across the filter area whilst the grads are, well, graduated.  They let less light in at the top before fading half way down to clear transparent plastic which lets all the light in.

As they let less light in they either cause your exposure to change (making it longer) or if you keep your exposure constant and they cause your image to record less light, so bright overexposed skies can be brought back into the world of colour.

A typical situation is a sky and land pic like the one above where the land is less bright than the sky and if you expose for one the other is not right-too dark or to bright.  Say the sky needs 1/60 sec and the land a 1/15; it can all be slowed down to record at a 1/15 second with a two stop grad placed over the sky (1/60, 1/30 is two stops making the sky now record at a 1/15).

It’s a time honoured way of getting all the brightness levels in your shot into one exposure and in the days of film I did it all the time because you had to get your exposures right in camera.  The grads cause only the dark part to record less light whilst the clear part lets in all the light.  These are perfect for sunsets where the sky is much brighter than the stuff below the horizon.

The ND’s are more useful for slowing the whole world down; flowers bobbing in the breeze blur to a soft, artistic blur, water becomes soft and ethereal and people become creative abstracts as they toddle down the road.

 

Greeen Arch, Pembrokeshire.  This was shot during the midday sun.  It was quite boring and I wanted to try and get something interesting after a trip out here so I used a 80A cooling filter to send the white balance blue and a 3 stop ND over the whole lens to slow the exposure down.  Nikon FM, 35-105mm, Fuji Velvia, f22 exposure not recorded.

I’ve found that the Lee grads are actually large enough to serve as an ND as well; if I want total ND coverage I pull it down to cover the whole lens.  Of course I then lose this grad if I also need to stop the sky down to keep it in touch with the foreground but I can usually get away with using one of the others in my set to do this job.

So which filter do we use and when?  I used to have various filters in my kit bag; 81 series warming filters, 80 series cooling ones, magenta and, whisper it please, a sunset graduated filter.  Yeah, it was pretty nasty looking when I look back now but at the time, before being able to tweak white balance with the nudge of a slider in Photoshop, it was a good option on an insipid dusk.  Add to that the goddess of ‘good light’ is a cruel mistress and these filters helped shape the colour temperature (white balance) of the light to our will when the chips were so often down or you needed to add some warmth to a cool, cloudy day.  Since the advent of The Digital Age and all the white balance controls at our disposal I now just carry the following Lee filters:

• 0.9ND grad (soft)

• 0.6ND grad (soft)

• 0.3ND grad (soft)

• circular polariser

I also have the following from B&W because a) it’s affordable and b) it’s readily available:

• 10x ND

Summit of Mount Kinabaloo, Sabah, Borneo.  It took me two days to hike up here and a 2am start to ascend to the summit for dawn.  The air was so thin I had to pause for breath every few paces and I was still fresh out of the Marines and couldn't have been much fitter.  However an insipid dawn broke and rather than accept defeat I reached for my trusty sunset filter to send the grey clouds into ecstasy!  Canon EOS 500, 28-80mm.  Exposure details not recorded.

These decimals are all ‘stops’ so a 0.3 is one stop, a 0.6 two etc.  If we refer back to our example above, you would use your meter to gauge the difference in exposure required to record both the sky and the foreground, work out how many stops this is and then slap on the appropriate graduated filter.  Once you’ve aligned the transition zone carefully over the horizon  and set your exposure for the bottom, clear part you’re good to go.  For landscape work, you don’t need the colour filters because you’ve got a white balance slider to tweak your RAW files with in post-production.

The ‘soft’ refers to the transition between the dark and the clear bits.  I’ve always used the soft on the basis my horizons are not always dead level seascapes.  The soft transition is a bit more forgiving than the hard one.  I’ve also wondered if the hard ones might be more obvious in areas where they don’t quite cover all the bright areas, say in a undulating mountain horizon where you could get some distracting ‘hot spots.’  It’s personal choice.  If you have the wonga get a set of each…

Giants Causeway, Northern Ireland.  For a brief spell I used a Mamiya 67II.  Great lenses but it wasn't TTL so you couldn't see where you had placed the ND grad.  You can see it was too high here by the light band across the horizon.  This can easily happen with TTL digital cameras if you aren't careful or if you choose not to place it over the nice sunlit rocks because they will also be darkended as they poke above the horizon.  Mamiya 67II, Velvia, 45mm lens, exposure details not recorded.

You can order these filters from Warehouse Express or Robert White, amongst others, but please keep a stiff to drink to hand before you see the prices.  Don’t say I didn’t warn you.  There are other manufacturers out there, Cokin being the one I’ve used, but Lee are the only ones to have truly neutral filters.  By this they mean there’s no colour cast.  The shot below of Dunstanburgh was a very long exposure on a lovely piece of Fuji Velvia (cue nostalgic tear) but the magenta colour cast is entirely down to the filter. Here it works, most of the time it doesn’t.

 

Dunstanburgh Castle, pre dawn.  A clear sky haeralded a fairly plain sunrise-none of the usual fiery fun with clouds present-but the composition was good so I went for it anyway.  With my Cokin ND grad on I held the brighter sky exposure in check and recorded the scene well.  However, the strong magenta cast from a very long exposure has really leaked into the film.  I think it works here but you wouldn't want this happening all the time...Nikon FM, 35-105mm, Velvia, f22 exposure of over a minute.

In case you thought the expense stopped here, think again.  This is photography and, apart from yachting and Formula 1, there’s few things in life more expensive.  You  need a filter holder which attaches to your lens via a special adaptor ring which you screw into the thread of your lens.  I have a ‘wide angle’ adaptor ring so the filter holder can go onto my 17mm lens without vignetting too much.  Obviously there’s a slight premium to pay for this ‘special’ adaptor ring.  You could be at the Nurbergring in the corporate seats by now….

The filters slot down nicely into the filter holder that clips onto the circular bracket screwed onto the lens' thread.

The bracket clips onto this adaptor ring (it’s actually a great design) and there are slots to put your filters in.  You can have from one to four but I only use two and I’ve never needed more.  If you also own the Lee Circular Polariser this can also be used in conjunction with this filter bracket if you wished to combine the filters for your shot.

Now, a word of caution.  I hate putting excess plastic in front of my lens.  Good lenses cost a fortune and they are very sharp so I don’t want to introduce reams of inferior quality filters for the light to go through before it enters my lens.  Flare can be exaggerated and the sharpness can deteriorate.  I find a polariser and one grad is enough, any more is done where absolutely necessary.

So there we have it; a filter kit for the 21st Century landscaper.  But, as I said in the intro; why even bother when you can merge exposures in PS?  You can dispense entirely with filters and go down this route.  If you’re field skills are up to it and you understand your histogram and how to record all the details in all the tones you can shoot a series of exposures and merge them all later on.  This doesn’t mean HDR in the whacky, and frankly unpalatable, sense that some use it.  It means bringing all the tones into line with what your eye sees rather than the limited tonal range your sensor can record.

However, it’s time consuming, both in the field and even more so later on in the digital darkroom and it can be very frustrating if you aren’t au fait with some fairly advanced PS techniques in this regard.  I see poorly blended exposures all the time-even amongst some well published pros and it’s bad form.  It completely lets the image down.

Add to that you’re giving yourself a headache when you have something like fast moving clouds in the sky.  If you shoot a series of images and in each one the clouds are in a different spot it’s virtually impossible to blend them together without ghosting from one cloud appearing in the next.

Personally, I’m using my grads about 40% of the time.  I probably should use them more.  I like to use them mainly to control the brightness range between the sky and foreground but also to slow exposures down to blur water or the movement of clouds in the sky.

I also find if I can get it substantially right in camera, it saves me time in front of that damn machine at home.  Honestly, I feel like Gollum sometimes after a marathon session of exposure blending leaves me pallid and square eyed.  Getting it right in camera harks back to the disciplined approach of the film days, rather than the lazy ‘fix-it-later-in-photoshop’ approach often relied upon today and I like that ethos as much for the time saving as the technical competence of getting it right at the time.

 

White Cliffs of Dover at sunset.  Well, near Folkestone, but Dover sounds better...Anyway, here I wanted to blur the water slightly but with everything so bright, even at ISO 50 my exposure was too fast to record movement.  The 3 stop 0.9 ND grad was duly called up and deployed across the whole frame to slow the whole exposure down.  I could have used one across the sky/cliff too at an angle to hold back that brighter part of the scene but with one ND filter and my polariser already in place I opted to exposure blend that bit instead.  EOS 5DMKII, 17-40mm, 1.3 secs at f13, ISO 50.

So like many things in life, there’s a place for both the new and the old to co-exist together-a happy medium.  My ND filters are indispensable to me-they save me from technical limitations of my cameras sensor in terms of recording a limited tonal range and they offer many creative options I couldn’t do without.  Sure, they are next to useless in a slot canyon but now we have the means to blend exposures via a series of digital files and this process can rescue us in these circumstances.  By using both these options I find I have more or less all the solutions I need to taking just about any landscape scene I am presented with.

Coming up next…a piece illustrating the various decisions on how to choose to filter, to exposure blend or, just maybe, to do a bit of both…

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