Nick Miners Photography

It’s a little late in com­ing, but I did prom­ise a les­son in how to use gradu­ated fil­ters. It fol­lows on nicely from what I spoke about in my post about the Zone Sys­tem, so please famil­i­ar­ise your­self with that one before read­ing this if you haven’t already; this one will make more sense that way.

I men­tioned that the range of bright­ness that a cam­era can ‘see’ is much nar­rower than that of the human eye. In most cases, you can isol­ate an inter­est­ing part of an image and bring out the detail where it’s rel­ev­ant, how­ever there are many situ­ations where this simply doesn’t work. For example, if you are tak­ing a land­scape pho­to­graph that includes a lot of sky, espe­cially late in the day, the fore­ground will gen­er­ally be three or four stops darker than the sky. By meter­ing for the fore­ground, the sky will be blown out, but if you stop down to increase detail in the sky, the fore­ground will usu­ally become too dark.

Of course, with RAW files and soph­ist­ic­ated post-​​processing tools such as Adobe’s Pho­toshop Light­room, it can be easy to fix such pho­to­graphs after­wards, but this won’t always work, as often the sky is so over­ex­posed that the high­lights end up edged with grey as col­our detail is lost. HDR is another option, but is time con­sum­ing, and the effect is not to everyone’s taste (myself included). It is far prefer­able, I believe, to achieve the effect you want in-​​camera. So how do you do this?

Take the fol­low­ing pic­ture of the church at Prest­bakki in north­ern Ice­land as an example:

Ori­ginal image

There is some great detail in the fore­ground, with the gravel and the weeds among the flag­stones clearly dis­cern­ible, but the sky is almost pure white. I could stop down by 2 stops to bring the clouds into detail, but then we lose the inter­est­ing tex­tures on the ground:

Under­ex­posed by 2 stops

How­ever, by apply­ing a 2 stop neut­ral dens­ity gradu­ated fil­ter (usu­ally referred to as an ND grad) with the dark half placed so that it cov­ers the sky, I can keep strong detail in both halves of the picture:

2-​​stop ND grad fil­ter applied to sky

This is a par­tic­u­larly strong set­ting, mainly for illus­tra­tion. The best use of ND grads is when you can’t tell it’s been used. Com­pare the next two pho­tos of the river Lagan in Belfast:

Without fil­ter

With 2-​​stop ND grad

The first was taken as is, and for the second I used an ND grad to drop the sky down 2 stops so that it was the same bright­ness as the river. The con­trast between reflect­ive sur­faces (such as water) and sky will always be less than that between, say, grass and sky, so it’s pos­sible to make the whole pic­ture appear more uni­form. This is another com­mon use for ND grads where you won’t neces­sar­ily get the same loss of detail caused by excess­ive dif­fer­ences in brightness.

Finally, an example of where an ND grad really comes into its own:

2-​​stop ND grad used

This was taken at Thirlmere reser­voir in the Lake Dis­trict. The sky was turn­ing some beau­ti­ful col­ours, but the bracken was a lovely shade of orange/​brown and the dry­stone wall provided a nice way to draw the eye into the pic­ture, so I placed my usual 2-​​stop ND grad on so that I was able to cap­ture the lot.

Note that there are many types of ND grad fil­ters. They vary from 1– to 4– stops, and in the degree of grad­a­tion, with a hard edge for clearly defined hori­zons, and softer edges for when fore­ground detail (e.g. trees, tall build­ings) intrude on the sky and would be spoiled by excess­ive dark­en­ing. It’s a good idea to have more than one to hand, but you can vary the soften­ing effect by using the aper­ture. A nar­rower aper­ture (higher ‘f’ num­ber) will harden the bound­ary between dark and light halves, so open up as wide as you can if you want a softer edge without chan­ging fil­ters. You can also buy screw-​​on ND grads which rotate inde­pend­ently of the lens, but you can’t move the hori­zon up or down with these, so it’s bet­ter to get the rect­an­gu­lar acet­ate fil­ters in the Cokin or Lee series.

I hope this les­son has also been help­ful. Please use the com­ments below to let me know if I’m strik­ing the right tone. I’d also like to see any pho­tos you take using ND grads; you can link to flickr if you have any you’d like to share.

What I’m going to try now is the first in a series of little les­sons, where I’ll show you some aspect of pho­to­graphy of which the aver­age point-​​and-​​shoot snap­per may not be aware. Hope­fully if you put these les­sons into prac­tice you’ll be able to achieve the sort of pho­to­graphs you’ve always wanted to. Let me know if I sound too pat­ron­ising; that’s not my inten­tion at all.

The zone sys­tem was developed by the Amer­ican land­scape pho­to­grapher Ansel Adams, and the prin­ciple is simple. A cam­era can ‘see’ a more lim­ited range of bright­ness than the human eye, so it needs to be adjus­ted to take into account light­ing con­di­tions. Most cam­eras try to render a scene so that the over­all light­ness is what’s known as 18% grey, or exactly half way between pure black and pure white. If we num­ber these bright­nesses, 0 for pure black, 10 for pure white and 5 for 18% grey, then by filling in the num­bers in between we have the 11 zones of the zone sys­tem. Each zone is 1 stop brighter than the pre­vi­ous one.

The zones mapped to an expos­ure meter

Most mod­ern SLR cam­eras, digital or film, allow you to over– or under­ex­pose by up to 2 stops in auto or semi-​​automatic mode, which can be lim­it­ing, so the first thing to do when using the zone sys­tem is to switch to full manual mode. The next thing to do is to set your cam­era to spot meter­ing mode; refer to your camera’s manual if you’re not sure how to do this. You are now equipped to try the zone system.

Each zone has a descrip­tion of what it represents:

0 — Pure black
1 — Near black, with slight ton­al­ity but no tex­ture
2 — Tex­tured black; the darkest part of the image in which slight detail is recor­ded
3 — Aver­age dark mater­i­als and low val­ues show­ing adequate tex­ture
4 — Aver­age dark foliage, dark stone, or land­scape shad­ows
5 — Middle gray: clear north sky; dark skin, aver­age weathered wood, grass
6 — Aver­age Caucasian skin; light stone; shad­ows on snow in sun­lit land­scapes
7 — Very light skin; shad­ows in snow with acute side light­ing
8 — Light­est tone with tex­ture: tex­tured snow
9 — Slight tone without tex­ture; glar­ing snow
10 — Pure white: light sources and spec­u­lar reflections

What you need to do to apply it is to find a key part of your pho­to­graph that you can assign a zone to, then set the expos­ure accord­ingly. In the illus­tra­tion above, I have mapped the camera’s expos­ure meter onto the middle 5 zones, but that does not mean you are lim­ited to just these zones — by using full manual mode you can go bey­ond these zones but you need to count!

Now let’s take an example. Sup­pose you are in a forest on a sunny day, where the grass on the floor is partly lit by sun and partly in shade. The most effect­ive way of expos­ing such a scene is to meter on the sun­lit grass, and the rest will take care of itself. Point your camera’s spot meter­ing zone at the grass so that the grass fills the meter­ing zone, and adjust the expos­ure so that the cam­era says ‘0’ — i.e. per­fectly exposed (or zone 5). You can then recom­pose, and because the cam­era is on manual, the expos­ure will not be affected. The res­ult will be some­thing like this:

A cam­era set to full auto would have seen the sil­hou­et­ted trees in the back­ground and over­ex­posed by a stop or two, to look some­thing like this:

Note how the vivid green in the fore­ground in the first pic­ture has been bleached out, and the stump is not as isol­ated as a fea­ture as it was.

Gen­er­ally you will be able to find a part of your pic­ture that fits within zones 3–7 so you can see your cam­era show­ing you how far over– or under­ex­posed you have made it. How­ever if you want to ven­ture fur­ther into the more extreme zones, here’s where you need to count. To expose for zone 2, set the expos­ure to under­ex­pose by 2 stops, then decrease the aper­ture or the shut­ter speed by 3 more clicks of the wheel (if your cam­era meters in ¹⁄₃ stop incre­ments, as in the illus­tra­tion above) or 2 more clicks (if ¹⁄₂ stop). For zone 1, use 6 or 4 clicks, and 9 or 6 for zone 0. To achieve a sil­hou­ette, for example, you should ensure the object you want to appear in sil­hou­ette is at zone 2 or below, but bear in mind that you may lose detail in the back­ground if it is not bright enough, so take another read­ing from the back­ground to ensure that you keep it in zone 5 or higher. If the con­trast between the back­ground and the object isn’t great enough, you prob­ably won’t be able to achieve a per­fect silhouette.

I hope this has all made sense; by all means look on the inter­net for more about the zone sys­tem and how a cam­era meters, but if you do get any good res­ults using this sys­tem I’d love to hear from you.