Filters in landscape photography
Author Andy Mumford |
 |
Digital and film cameras are
fantastic pieces of equipment, but they can never capture the world in the way that we see
it.
Our eyes can take in a huge range of contrast across a scene, from a brightly lit sky to
the shadows on the side of a rock without struggling, while a camera can only record a
small amount of that range before losing detail either in the shadows - the featureless
slabs of black, or in the highlights - the bright white parts of a photo often referred to
as "blown" or "clipped" highlights.
In fact most digital cameras can only record around 5-7 stops of contrast in a scene, and
anything that falls outside of that latitude will be lost detail, either black or white.
This is a particular problem in landscape photography where we may want to shoot into the
light at sunset to record vivid colours in the sky, but also include plenty of detail in
the foreground, perhaps around rocks on a beach, or grass in a field. |
|
|
|
There are various solutions to this, but
for me the most effective and natural is to use neutral density graduated filters.
An ND graduated filter is a rectangular filter where the top half is a neutral grey
(meaning it should have no colour in it) while the bottom half is clear.
They work by placing the dark part of the filter over the sky, which reduces the light
passing through to the sensor in that area, giving less exposure. The clear part of the
filter, which is covering the foreground, remains unchanged.
These filters come in two kinds; with a "hard" graduation, where the transition
from the dark part to the clear part is very abrupt and "soft" graduations,
where the transition is more subtle.
Hard graduations work better in scenes with a clear horizon line, like the ocean, while
soft graduations are more suitable for less defined horizons, like when shooting mountains
or rolling countryside.
The filters are also available in different strengths, or "graduations" from 1
stop to 3 stops.
OK, so that's what they are, but how we use them?
Well, first of all, it's important that we understand a little about the way a camera
meter works to use them effectively. Most modern camera meters work by reading the light
from all over the scene and giving an average. As the camera's range can't cover the whole
of the scene, this average is bound to mean some compromise resulting in either lost
shadow or highlights. |
|
|
|
The easiest way then to meter such a scene
is to cut all the sky out by filling the viewfinder with the foreground. This will give us
an average of the foreground which most of the time will be within the cameras exposure
latitude. With the camera in Manual mode, set the exposure that the camera indicates.
Then, point the camera at the sky that you intend to photograph, and see how much brighter
it is. Camera's differ, but on my Nikon one of the bars in the viewfinder's exposure
indicator represents half a stop, so I can usually see how much brighter the sky is
through the viewfinder.
Alternatively, just change the shutter speed until the sky is correctly exposed and work
out how many stops there are between the sky exposure and the foreground reading you did
first.
For example, in the shot below of the tree, I pointed the camera so the foreground grass
completely filled the viewfinder, and set the camera to exposure that the camera's meter
suggested, which was 1/2s at f8. |
|
|
|
|
|
I then
pointed the camera at the sky, which gave me a reading of 1/30, five stops brighter than
the reading for the foreground.
I always try to keep every part of an image within a five stop range, so if 1/2 is my base
exposure, I try to pull everything to with 2 or 3 stops of that. Placing a 3 stop ND
graduated filter across the sky in this image pulled the sky back into the camera's
latitude and enabled me to record the entire scene and keep the rich colours of the sky,
as well as the green of the grass in the foreground field.
Of course, metering can be even more accurate using a spot meter and taking readings from
various parts of a scene, from the darkest shadows and brightest highlights (for example
sun reflecting off water) in the foreground. For the shot below, I spot metered the the
shadows in the rocks as well as the brighter parts of the water. None of these areas would
be covered by the filter, so I wanted to ensure that all of it would be within the 5 stop
range. As it happened, it was a little too much, so I had a choice between losing
highlights in the water or shadows in the rocks. In these situations I'll usually choose
to lose shadow detail as I believe the eye more naturally accepts black shadows than
bright white spots.as long as the shadows aren't too big.
|
|
|
|
As the sun was just breaking the horizon, the sky was considerably brighter than the foreground, so I
needed to use 5 stops of ND graduated filter (a 3 stop and a 2 stop), but even so, I knew
I would lose some highlight detail around the sun.
Filters are also extremely useful when shooting reflections. Reflections are usually
around 2 stops darker then the sky they reflect, although this isn't apparent to our
eyes-
Again, the same metering process can be used to establish the different exposure values.
In the shots below taken in the Amazon, I didn't include any foreground, so the exposure
was very straightforward, the sky was 2 stops brighter than it's reflection in the water,
so I placed a 2 stop graduated filter across the top half of the image.
|
|
|
|
When
shooting reflections though it's always important to not over filter the sky. A sky which
is actually darker than it's reflection will always look a little strange to our eyes.
When it comes to buying filters, there is a wide choice available.
Cokin P series for example are very affordable and easy to get hold of. However, they are
relatively small, just 85mm wide, and the filter holder will almost certainly vignette and
appear in the corner of your images if you shoot wide angle shots.
Also, cheaper filters are prone to colour casts, adding a slightly different colour to
your images, which can be extremely irritating.
It's better to buy the best quality filters you can afford because, like your tripod and
lenses, they are an investment that will improve your images and should last longer than
your camera body.
For me, 100mm Lee filters are the best quality filters available. They have no colour
cast, are wide enough to shoot even at 15mm (at 35mm equivalent) and are very solidly
made.
|
|
Andy Mumford Official Website:
www.andymumford.com |
|
|
|
|
|
