For beginning photographers,
there comes a pivotal moment to understanding the limitations of
how much can be recorded on film or with digital sensors. This moment
came for me on a road trip where I came upon a great sunset. Beautiful
colors, vibrant green hillsides, cows munching . . I wanted to capture
this moment. I pull over and snap the picture with my new fancy
camera. Not sure how to work all the settings, I just let the camera
decide on exposure. The next week I see the results of my effort
when I get the film back. Disappointing!
The sky was close
to what I had seen (the camera was pointed up enough so that it
metered from the sky) but the beautiful pasture and cows were only
a silhouette. This was my first visual lesson that film (and digital)
cameras can only reproduce a 3 to 4 stop difference in lighting.
An example of how
this may occur for a typical sunset goes as follows. You point the
camera up to meter off the sky. For a given aperture, the shutter
speed is indicated as 1/500th. You then point the camera down to
meter the foreground and read 1/30th. This represents a 4 stop difference
in exposure. (counting down from 1/500th: 1/250th, 1/125th, 1/60th,
1/30th) The guessing game then starts, what do I set the exposure
to? 1/500th will get you a great sky with a silhouette for the foreground.
1/30s will give you detail in the foreground, but the sky will be
"blown out" with the vibrant colors replaced by drab gray
Settling for a
middle exposure of 1/125s doesn't work well as nothing looks good.
There are several techniques for dealing with this issue, and one
of the best is using a graduated neutral density filter.
Neutral Density (ND) filters are somewhat like
sunglasses for you camera. Good ones simply reduce the quantity
of light entering the lens (with little color shift). A graduated ND does just as it says - the portion of filter that is dark is
graduated over it's surface with half being clear, the other half
being dark, and a portion between being a smooth transition between
dark and clear.
There are several
decisions to make regarding what type of graduated ND filter to
choose. First is the type. You can get a graduated ND filter in
a round shape that screws onto the front of your lens. You can also
get the graduated ND filter in a rectangle that fits in an adaptor
that attaches to your lens. I can't comment on the round type as
I have never used one. The reason I discounted round ND grads is
that you can't change where the transition from dark to light occurs
in your framing. If you always take pictures with the horizon in
the dead center of your frame, then you may be in luck. For the
rest of us, go with the rectangular variety. In my experience, being
able to set the transition area precisely greatly increases
your options in composition.
The next decision
is how dark do you need the grad ND to go? The filters are usually
sold in 1 stop increments where a 0.3 ND will reduce the light entering
by 1 stop. A 0.6 reduces by 2 stops, 0.9 by 3 stops, etc. The example
above would in theory require a 1.2 ND grad (4 stops). I say in
theory because there are times that you do not want to balance the
foreground and background exactly - you may want the foreground
to be 1 or 2 stops darker than the meter indicates as this may make
your picture more natural looking. It is best to experiment with
1 filter under different circumstances to see if the results are
too obvious. Since ND grads are sometimes not offered in a 1.2,
you would settle for a 0.9 to reduce the sky exposure by 3 stops.
below is an example of what a ND filter can do for you. It is not
scientific and far from perfect as the exposure was not exactly
the same for both - the foreground is a little darker in the example
with the filters. It is also is not only a demonstration of the
ND grad as I also added a polarizing filter.
This picture from Puerto
Rico was taken with no filtration. The detail is good
in the foreground but the sky is a total loss of detail.
Same setup, same time of day, but this
time I used a polarizing filter along with a Hitech 0.6 soft ND grad. Again, this example is not perfect because I lowered
the exposure slightly as you can see with the darker foreground.
Rest assured that most of the detail gained in the sky is
from the ND grad. I positioned the transition on an angle
to match the contour of the wall.
I mentioned in
the description above that I used a soft ND grad in the example
above. This brings us to item #3 to decide on. ND grads are sold
in "soft" and "hard" varieties. This refers
to the transition area between dark and clear. A "soft"
ND grad will have a longer (more gradual) transition area between
the two while a "hard" will have a shorter and more abrupt
If you are taking
a picture of a sunset with an entirely flat horizon (such
as in Amarillo Texas), then the hard variety will be better
as it will allow you to transition quickly and match the contour
of your subject. If, however, the transition between light and dark
in your subject is more irregular (like the example above) you are
much better off with a soft ND grad.
The illustration above shows differences
between two ND grads that I use. On the left is a Hitech 0.6
and on the right is a Hitech 0.9 hard. You can see the
1 stop difference in that the 0.9 on the right is darker.
Also notice that the transition area is longer on the 0.6
soft shown at left.
First meter off the sky, then meter
off the foreground to see what you are working
with. Even if you don't have a spot meter (either
separate or built into your camera) you can make do
by selecting center weight metering and making sure
to aim the camera high (and then low) enough to encompass
all of your subject.
Next, determine what strength of
filter to use. This will be dependant on what filters
you have available. Don't think you need to buy all
of them. In fact, I would recommend you just choose
one and learn how to use it. If your metering determines
a 5 stop difference and you only have a 0.9 (for 3 stops)
use it and see what happens.
Err on the side of under correcting
rather than over correcting. If you use too strong of
a ND grad, you will end up with sky that looks dark
like the last light of evening and a foreground that
looks like the middle of the day. If this is the effect
you are looking for, then go for it! However, know that
this may appear unnatural. Gaylen Rowell was notorious
for going a little overboard in using ND grads that
were a little strong and left the foreground very bright.
Having said that, all the examples I would complain
about are leaps and bounds better than I have ever taken,
so go with what you feel will give you the best results.
Err on the side of positioning the
transition too low. You usually want the sky in your
composition completely covered by the dark area of your
ND grad. If the horizon is uneven, this will mean lowering
the filter so that the lowest point is completely covered
or the filter is set at an angle. If you set the ND
grad too high, it will leave a stripe of blown out sky
just above the horizon. This looks very unnatural. For
a sunset shot, the region that needs held back the most
is the area right over the horizon (where the sun is)
so you want to make sure it is covered.
Seeing where the filter transition
occurs through the lens can be difficult. To make it
easier, use the following method: Set the lens to a
small aperture, around f16 or f22. With one hand, stop
the lens down by holding down the appropriate lever
or button. While looking through the lens, use your
other hand to wiggle the filter up and around. You will
be able to clearly see the transition region moving
around. Keep the lens stopped down and slide the filter
to completely cover the sky. Make sure to readjust your
aperture if necessary before taking the shot.
I would encourage
anyone learning about photography to take the jump and use this
amazing tool. To begin with I would recommend the following setup
for most 35mm or digital setups:
Cokin P type holder
and the appropriate
adaptor to screw on the front of your lens. The P size
is a great compromise that will cover most lenses that
you will use.
Hitech 0.6 soft ND grad. I struggled with the decision
between soft and hard. I have both, but it turns out that I use the soft filter much more
often. Very few compositions are straight enough to confidently
use the hard ND grad. The soft is easier to use and will
often give more predictable results. 2 stops of correction
is good for most pictures that I take. The most vibrant
colors usually occur when the sun has gone down and the
sky is a bit darker. During these twilight moments, 3 stops is sometimes
too much and the 2 stop (0.6) is perfect.
- A stronger ND grad, such as the Hitech
0.9, is a good next addition. I chose to go with a hard
transition for the 0.9. It works well for some sunset
shots, but I generally find I reach for the 0.6 more often.