The Landscape Photographers Guide to Filters

Transcription

Why filters remain an essential tool for the Landscape Photographer
and how they can transform your work.
The Landscape
Photographers
Guide to Filters
www.lenscraft.co.uk
By Robin Whalley
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CONTENTS
Introduction ............................................................ 2
Why use Filters ....................................................... 3
Buying Filters .......................................................... 5
Filter Systems...................................................... 5
Screw in Filters ................................................ 5
Square Filters .................................................. 6
From Experience ............................................. 7
Filter Sizes ........................................................... 8
Manufacturers/Quality ....................................... 8
What Do I Use ................................................. 9
Accessories ....................................................... 10
Filter Adapter Rings ...................................... 10
Filter Holders ................................................ 10
Stepper Rings ................................................ 11
Adapter Caps ................................................ 11
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Compact Camera Adapters ........................... 12
Types of Filter & their use .................................... 13
Copyright © 2015: Robin Whalley
Colour Balance Filters ....................................... 13
B&W Contrast Filters ........................................ 13
Polarising Filter ................................................. 14
Neutral Density (ND) Filters .............................. 15
“Extreme” ND filters ..................................... 16
Neutral Density Grads ...................................... 18
Soft and Hard Grads ..................................... 19
Reverse ND Grads ......................................... 20
Infrared ............................................................. 21
Cleaning Filters ..................................................... 23
Summary ............................................................... 24
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INTRODUCTION
The use of filters in photography has been
around for many years. Not long ago they were
an essential accessory, but with the advent of
Digital Photography, many have decided they
can dispense with them. Whilst there may be
some alternatives to using filters, this isn’t
always the case and superior results can often
be achieved with their use.
record images in RAW format isn’t a
necessity for using filters, but the
RAW format will provide you with more
flexibility to replace some filters.
This guide will explain the various types of
filter, help you in making purchasing decisions
and provide instruction about when and how
you might want to use them.
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The guide makes three assumptions:
1. Whilst the information may be of use
in other photographic genera, it’s
been written for Landscape
Photographers.
2. You will be shooting digitally rather
than with film. Whilst the information
may also be of value for film
photography, the information is
designed for digital users.
3. You understand how to operate your
camera and that your camera can
record RAW format files. The ability to
USING FILTERS FOR IMAGES SUCH AS THE ONE ABOVE ALLOWS YOU
TO WORK MORE QUICKLY WHILST ACHIEVING PROFESSIONAL
RESULTS. WITHOUT A FILTER THE PIER WOULD HAVE TURNED
COMPLETELY BLACK OR THE SKY WOULD HAVE LOST ITS COLOUR.
FOR THIS IMAGE A 0.6 NEUTRAL DENSITY SOFT GRADUATED FILTER
WAS USED TO DARKEN THE SKY. A SOFT GRADUATE WAS USED AS
THE LIGHTHOUSE EXTENDED INTO THE AREA OF THE GRADUATE.
THIS MADE THE LIGHTHOUSE EASIER TO ADJUST DURING POST
PROCESSING.
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WHY USE FILTERS
There are many reasons why you might choose to
use filters, but all involve controlling the light
entering the camera. Such control might include:
1.
2.
3.
Adjusting the wavelength of light, for
example to make a cool light appear
warmer.
Restricting the wavelength of the light in
some way. Examples include allowing
only infrared light to enter the camera, or
polarising light.
Restricting the amount of light reaching
the camera sensor. For example, a
Neutral Density filter can be used to
reduce the level of light, so as to create a
longer shutter speed.
Of these three categories, the first can be easily
(and probably better) achieved using tools such as
Lightroom and Photoshop. Lightroom for example
has the Temperature and Tint sliders in its Develop
module, which allow you to control the colours in
your image better than any filter.
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The other two categories are more difficult to
replace with software and some effects may not be
possible at all. Filters in these categories are the
ones we should consider as being essential.
Even where software alternatives do exist, they are
often more difficult and time consuming than
using a filter. Remember, physical filters that
attach to your camera and lenses will often save
time and allow you to concentrate on taking the
photograph.
The image on this page used a 0.9 Hard Graduated
Neutral Density filter on the sky. This was
necessary to record detail in the beach, harbour
and houses. Without the filter, these areas would
turn black.
The same result could be achieved by taking two
separate images, one exposed for the sky and the
other for the land. These could later be blended
together in post processing, using Photoshop.
This approach would though have been much
more time consuming than using a filter. It would
have been more time consuming at the point the
image was taken. It would have been more prone
to making mistakes, as I would need to adjust the
camera to take two or possibly more exposures. It
would have taken much more time in post process
and it would have necessitated using a tripod
(which I didn’t have with me at the time) in order
to align the various images. By using filters, it was
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possible for me to shoot a single image handheld,
recording the scene as I wanted.
A 0.3 NEUTRAL DENSITY GRADUATED FILTER WAS USED WHEN
TAKING THE 4 IMAGES THAT COMPRISE THIS PANORAMIC.
ALTHOUGH THE FILTER IS QUITE WEAK, IT’S SUFFICIENT TO HOLD
THE DETAILS IN THE FOREGROUND TREES. WITHOUT THE FILTER THE
TREES WOULD BECOME A DARK MASS AND THE IMAGE WOULD LOSE
ITS APPEAL.
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BUYING FILTERS
When it comes to buying filters there are a few
considerations you need to make:
1.
2.
3.
4.
becoming damaged. They also protect the lens
from becoming dirty, as cleaning a lens always
gives rise to the risk that small scratches will be left
on the glass surface.
even becoming visible. This usually isn’t a problem
where you only have a single filter screwed to the
lens, but once you have two or more, problems
can quickly arise. Wide angle lenses are particularly
susceptible to this problem.
Type of filter system
Manufacturer and quality
Useful accessories
Which filters types you might need
FILTER SYSTEMS
Filters systems fall into two categories:
1.
2.
Screw in filters that screw to the filter
thread of your camera lens
Square filters that slot into a filter holder.
The filter holder then attaches to an
adapter that screws to the front of your
lens.
Each of these systems has advantages and
disadvantages that you should consider.
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SCREW IN FILTERS
Screw in filters are round and screw on to the front
filter thread that most camera lenses have. As an
example, it’s very common for photographers to
buy a screw in UV filter or a clear glass protector
filter. These are then left attached to the front of
the lens to minimise the chance of the lens glass
Above you can see an example of vignetting on a
wide angle lens where two screw in filters have
been stacked together.
Screw in filters come in various sizes and you
should match the same size to the lens. If you have
a 77mm diameter lens, then you need to buy a
77mm filter. The downside is, if you have lenses
with different diameters, you need to buy the
same filters multiple times, once for each size.
Another downside to this design is that it can
cause problems with vignetting. This is where the
edge of the filter extends into the edge of the
frame, so darkening the corners of the image or
Despite these problems, some filters are
particularly well suited to the screw in design.
These are:



Neutral density filters, as the design helps
to minimise stray light entering the lens.
The polarising filter, as the design allows
you to turn the front element of the filter
to adjust the polarising effect.
UV or clear glass protector, as the design
prevents the filter getting in the
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photographer’s way, allowing it to be left
permanently attached to the lens.
So far we have assumed you will be able to attach
a filter to the front of your lens. Most cameras with
interchangeable lenses have a screw thread at the
front, which can be used to attach a filter or
adapter. There are though exceptions to this so it
is worth checking your lenses if you are unsure. If
you find your lens doesn’t have a filter thread,
there may be alternatives. A good idea, especially
with more specialised lenses is to contact the
customer services team of the filter
manufacturers.
If you are interested in using filters with a compact
camera, it’s quite likely that you will have this
problem. It’s common for compact cameras to not
have a threaded front lens so you need an
alternate means of attaching a filter. We will look
at this problem and some solutions in the
Accessories section of this guide.
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SQUARE FILTERS
The other system you will come across is the
square filter system. These filters are flat squares
of material that slot into a filter holder. You can
see an example of a simple set up from Cokin
below. This has three elements. Firstly, the adapter
ring that screws to the front of your lens. Then
there is the filter holder which clips to the adapter
ring, securing it to the front of the lens. Finally,
there is the filter itself, in this example a Neutral
Density Graduated filter.
Once the filter holder is attached to the filter ring
at the front of the lens, you are able to slot your
filters into the holder. This is very useful where you
have filters such as the Neutral Density Graduate
(or ND Grad), as it allows you to reposition the
filter. If you were using the screw in type filters
with an ND Grad, you would find that you often
need to change your composition to align the
gradient correctly with the horizon. With the
square system you only need to slide the filter up
or down in the holder, possibly also rotating it left
or right.
Where square filter systems don’t always perform
well is with strong Neutral Density filters used for
long exposure photography. You can sometimes
find that the filter doesn’t sit flush against the lens,
causing light to leak in around the edges of the
frame. To address this, some long exposure filters
have a gasket glued to them to help seal any gaps.
You can see an example below.
The square filter system can also suffer from
problems similar to those of screw in filters. For
example, the filter ring adapters that screw to the
front of the lens can cause vignetting as can the
filter holders themselves. If you are using wide
angle lenses it may be necessary to buy larger,
more expensive filters. We will look at the choice
of filter sizes in a moment as well as special
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adapter rings that can help reduce the possibility
of vignetting.
It is possible for you to mix the two types of
system. For example, you might choose to attach a
UV filter to the front of your lens but then attach a
screw in filter adapter (for a square system) to the
front of the UV filter. This can however increase
the possibility of vignetting problems so it’s
important to pick the right filters and accessories
to pair up.

I do own some standard Neutral Density
filters of the screw in type. I use these to
lengthen exposure with my Micro 43
cameras but generally I prefer working
with the square system.
FROM EXPERIENCE
It’s very unlikely that a single filter system will
meet all of your needs and you will end up
combining systems. The best advice I can give is to
work out which filters you need and which system
is best suited to each. My own approach is
summarised below:


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
I have a screw in UV filter or clear glass
protector attached to the front of each
lens I own. This is to help protect the lens
and make cleaning easier.
I have a square filter system which can be
attached to the screw in filters. With this I
use a range of ND Grad filters but also
long exposure Neutral Density filters.
The other filters I use are Polarising and
Infrared filters. These are of the screw in
type.
THE TEMPTATION TO PERFECTLY EXPOSE A SCENE IS ALWAYS THERE WHEN USING
FILTERS. WHEN WE PUSH THE BOUNDARIES OF WHAT’S POSSIBLE TOO FAR THE IMAGE
CAN BECOME FALSE IN APPEARANCE.
RETAINING CONTRAST IN THIS SCENE HELPS CREATE THE FEELING OF DUSK. THE
VIEWER WILL UNDERSTAND AND APPRECIATE THIS. KEEP IT REAL WITH LANDSCAPES.
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FILTER SIZES
If you already own a square filter system or have
been researching these, you will most likely realise
that you have a choice of filter sizes. Generally,
these are:






67mm
75mm
85mm
100mm
130mm
150mm
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To complicate things further, different
manufacturers have their own classification and
not every manufacturer supports all sizes. Here are
a few examples:
filter. They have now added a 150mm system
known as their SW150 range.
The idea behind the different filter sizes is that you
will need the larger systems when using wide
lenses (although this isn’t always the case). For
example, I have successfully used my Micro 43
equipment (Panasonic 14-45mm, Olympus 12-40
and Olympus 9-18mm lens) with the Hitech 67
filters. Surprisingly these filters work fine and show
no vignetting even with the Olympus 9-18mm lens.
In contrast, I sometimes have issues with my Lee
100mm filters on my Canon 16-35mm lens. The
problem is actually the filter holder as I have the
polarising ring attached on the front and it’s this
that can be seen around the edge of the frame.
As a general guideline, if you are using a Micro 43
system, consider using the 67mm or 75mm filters.
HiTech, who also trade under the name of Formatt
filters tend to include the filter size in the name of
the filter range. Currently they are producing filters
in the 67mm, 85mm and 100mm sizes.
At APS-C or full frame you probably need to move
up to a 100mm filter system, depending on how
wide your wide angle lenses are.
Another manufacturer, Cokin produce a 67mm
filter which were known as the A-series, an 85mm
P-series, a 100mm Z-series and a 130mm X-series.
They have recently taken to also branding these as
S (small), M (medium), L (large) and X (x-large).
If you are using ultra-wide lenses on a full frame or
APS-C camera, then you may need to be looking at
the 130mm-150mm filters. Personally I find these
too large to carry easily so will put up with some
vignetting. Larger filters also have a tendency to
catch the wind.
Lee, a well-respected manufacturer in the UK
produce a 75mm series which is known as the
Seven 5 series as well as their standard 100mm
Another factor that might guide you, or at least
rule out some filter sizes, is the diameter of your
lenses. It’s quite possible that you can’t find a filter
adapter for the size of lens. For example, you may
have a 37mm diameter lens for a Micro 43 system
cameras but you won’t find an adapter ring to fit
this with some of the larger filter systems. Be sure
to research your lens range.
A final idea if you are worried about filter sizes and
have yet to invest in a system, is to ask for the
experience of others on a camera forum. Try to
find people who have used the combination of
filter and lens you are interested. Just try to ignore
the views of those who give advice but don’t have
actual experience.
MANUFACTURERS/QUALITY
When considering filters and manufacturers, it’s
easy to overlook quality considerations. A common
problem with many Neutral Density filters is that
they aren’t neutral. Manufacturers will claim they
are, but experience shows filters can sometimes
still introduce a colour cast to images. With today’s
excellent digital cameras, any problem with colour
cast seems to become more obvious.
You can see one example of a colour cast in the
next image, where a 4 stop Neutral Density filter
was used to lengthen the exposure. Unfortunately,
the filter has a serious red cast and is anything but
neutral.
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The camera you use also seems to be a variable in
the problem. Different cameras appear to highlight
any colour cast present in the filters, more than
others. My Sony RX10 appears to be particularly
good at emphasising any magenta in my filters.
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Finally, the age of the filter may play a part in the
perception of neutrality. Even ignoring the risk of
scratches appearing on filters as they are handled
over time, I have some older filters that now
display a colour cast where I once believed them to
be neutral.
Some manufacturers appear to be better than
others at avoiding colour casts, but there can also
be variations over time. From my own experience I
have used filters from Hitech, Cokin and Lee. The
results from the Hitech and Cokin systems have
been inconsistent. Some have seemed to be
neutral but when I have purchased a replacement
the new filter produced a colour cast.
As if all these variables weren’t enough to contend
with, atmospheric conditions can also introduce
strange effects. Take the following example which
was shot using a filter that I know to be neutral.
There had been a strange atmospheric haze over
the landscape for a couple of weeks. On this
particular day the scene appeared neutral to the
eye even though the sun was starting to drop low
in the sky and warm up. On the back of the camera
in live view, the image just appeared “dirty”.
Several friends who were with me at the time all
experienced the same phenomenon with their
own filters.
WHAT DO I USE
At this point, I know some of you are asking
yourself what filter systems do I use. Here then is a
summary of my own past experience.
When I started in Photography I used Cokin PSeries filters and paid what seemed to be quite a
lot (I now know otherwise) for a set of ND Grads.
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These seemed fine when shooting slide film but
later I experienced a purple colour cast with ND
Grads when I switching to digital photography.
After buying a few more sets of Cokin and being
disappointed, I switched to Lee and their 100mm
system. These filters have been very good although
I have experienced the odd quality control issue,
which were quickly addressed by Lee.
When I switched to a Micro 43 system as my main
camera I found the Lee filters to be too large. I
therefore switched to HiTech filters and the 67mm
range. These have been good although I can detect
a slight colour cast under some conditions, with
certain cameras. This though is easily corrected in
post processing using the Lightroom Graduated
filter.
My current system is the Lee Seven 5 filter range
for use with my Micro 43 camera. The build quality
and neutrality of the filters is excellent. For my
Sony A7R (a recent acquisition) I have returned to
the Lee 100mm filters.
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ACCESSORIES
Today, you can buy a seeming increasing array of
accessories for use with your filters. With the
screw in variety you don’t really need anything,
other than perhaps a cleaning cloth and something
to carry the filters.
When it comes to the square filter system there
are a few more accessories to consider. Some
examples are:





Filter adapter rings
The filter holder
Stepper rings
Filter caps
Compact camera adapters
We can look at these now in a little more detail.
FILTER ADAPTER RINGS
These are the rings, usually made of metal, that
screw to the front of your lens and to which the
filter holder then attaches. It can be tempting to
think that the rings are interchangeable between
some manufacturers but you shouldn’t. By way of
an example, I was using filter rings for the Cokin P
series with a filter holder from HiTech given the
filters were both 85mm. The problem I
experienced was that the HiTech holder would fall
off at times and at other times become jammed on
the ring.
Later I also tried a Cokin adapter on the HiTech
filter ring and found these to be very stiff. It was
only then that I realised the HiTech adapter rings
were marginally thicker than the Cokin adapter
and had a lip. The message is simple, use the
adapter rings that pair up with the filter holder you
are using. Some rings may seem overpriced but
buying cheap alternatives can also be a false
economy.
A problem we mentioned earlier was with wide
angle lenses are prone to vignetting. Whilst one
solution could be to buy wider filters, this can also
be much more expensive, as well as more difficult
to carry. An alternative offered by some
manufacturers may be a wide angle adapter ring.
Lee for example offer a wide angle and standard
version of their adapter rings. These rings are
recessed and bring the filters nearer to the front
element of the lens. Whilst these cost more, they
are cheaper than buying wider filters. The risk is
that they may not entirely resolve the problem.
FILTER HOLDERS
Generally speaking, you don’t have much choice
with filters holders. Each manufacturer has its own
design and they also tend to vary this between
ranges. Some are very cheap (but do the job) such
as the Cokin all in one plastic holder, whilst others
are modular and more expensive.
The modular holders probably provide more
flexibility but they also tend to be a little larger and
bulkier. For example, my Lee 100mm filter adapter
is quite large and has slots for three filters. I can
though remove some of the blades to reduce the
depth of the holder, but it then holds fewer filters.
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Some modular filter holders such as those
provided by Lee and HiTech also allow you to
attach a filter ring to the front of the holder. It’s
then possible to screw a large polarising filter to
the ring and the front of the holder. This can be a
cost saving, allowing you to buy only one polarising
filter (which are usually very expensive) to use with
every lens. The downside to the polarising ring
approach is that it can cause some vignetting with
ultra wide angle lenses.
If you do decide to adopt this approach, don’t
automatically buy the polarising filter from the
manufacturer but shop around. With my Lee
100mm system the polarizer is 105mm diameter
and very expensive. Rather than buy the Lee filter I
purchased one by Heliopan. It saved my around
50% and the quality is superb.
STEPPER RINGS
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These are very cheap accessories but can save you
a lot of money. They screw into the front of your
lens and provide a thread at the end which is
wider. It’s then possible to attach wider filters
adapters to your lens.
new filter ring you could buy a much cheaper
stepper ring.
You can pay a lot for stepper rings but a quick
search on Amazon or eBay will turn up plenty of
very cheap alternatives.
ADAPTER CAPS
By way of an example, I recently purchased a
67mm diameter lens and filter ring adapter. The
filter ring was quite costly at £30 as it was the wide
angle type. Unfortunately, there was a fault with
the lens which I ended up returning. Rather than
buy the same lens again I purchased a much
cheaper lens that’s turned out to have excellent
performance. My problem is that the new lens is
only 58mm diameter and I don’t want to buy
another filter adapter. The solution is a very cheap
58mm-67mm stepper ring.
Another example is if you have an existing filter
system but a new lens has a diameter that you
don’t have a filter ring for. Rather than buying a
If you are using a square filter system, then you
might have noticed something rather annoying.
Once you have attached a filter ring to the front of
your lens, your lens cap no longer fits. This can
expose your lens to quite a lot of dirt. Yes, you
could remove the filter ring to attach the cap but
that starts to become time consuming and fiddley
when you’re standing in the dark in sub-zero
temperatures waiting for the dawn.
One rather neat and cost effective solution offered
by Lee is their 100mm filter cap.
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These are simple white plastic caps that clip over
your filter rings to protect the lens when not in
use. This allows you to keep the filter rings on the
lens so that when you need to attach a filter you
just pop off the cover.
COMPACT CAMERA ADAPTERS
With many premium compact cameras, the
manufacturers will provide a way of attaching a
filter (as well as try to sell you a rather pricey
adapter). It’s worth checking around on sites such
as Amazon and eBay to see what alternatives there
may be. This is also a useful way to find out if there
is an adapter for your particular camera model of
you don’t already know about.
Above you see a picture of an LX5 compact camera
with the front barrel ring removed to reveal a
screw thread. The barrel on these cameras houses
the lens which extends and retracts when the
camera is switched on and off. The idea of the
barrel thread is so that you can attach an adapter
tube that can accept a filter. The lens itself will
then extend and retract within the tube,
preventing it from coming into contact with the
filter. The front of this tube contains a thread into
which you can then screw your filter or filter
adapter. You can see the adapter tube in place in
the next image.
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Let’s take a look at one example of a compact
camera that can use filters.
One assumption to avoid making though is that a
premium compact camera will have a means for
attaching filters. Two surprising examples of
premium compact cameras I have owned, that
can’t have filters attached, are the Sony RX100 and
Canon GX7. Both were premium cameras and
nether have any way to attach a filter or filter
adapter.
My solution was to buy a special adapter from a
company in the US called Lensmate. They
manufactured an adapter that attached to the
front of the lens barrel using industrial double
sided tape. It sounds crude but it works very well
(although it’s a little overpriced in my opinion). If
you are struggling to find an adapter for your
camera, it’s worth contacting them or looking on
their website.
Let’s move on to look at the different types of filter
and how you might use them.
The LX5 example is only one solution that is
available for some Panasonic compact cameras.
When Panasonic released the LX7 as a
replacement for the LX5 they changed the filter
attachment doing away with the tube entirely.
Other manufacturers will have their own solutions
to this problem so you will need to investigate.
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TYPES OF FILTER & THEIR USE
This section of the guide will introduce you to the
many different types of filter and their possible
uses. But before we do this we need to consider
some of the rather “ugly” filters that have found
their way into photographers’ kit bags over the
years. Examples of these include rainbows, star
effects, fog, multiple exposures to name but a few.
Whilst it is possible to introduce some valuable
enhancements with these effects, I can’t
immediately think of any. If you do find yourself in
a position where you need to introduce one of
these effects, then please turn to software. It will
usually give a superior result with more flexibility.
There will be no further mention of such special
effects filters.
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COLOUR BALANCE FILTERS
When landscape photographers talk about light,
they often refer to light by its colour, even white
light. You may hear reference to warm light, cool
light or even cold light. What determines whether
light is cold or warm is the colour temperature of
light. When we see a sunset, it has a low colour
temperature (usually 3,000K to 4,000K) that makes
it appear golden. Equally, if we were to take a
photograph in the shade, the light can appear blue
because of the higher colour temperature (7,000k
to 9,000).
Today’s digital cameras are able to deal with this
range of colour temperatures and correct them
using their white balance feature. Often this is set
to Auto so that the camera automatically applies a
correction to produce a neutral white. You can of
course set the white balance to other settings such
as daylight, shade, tungsten etc. where you
determine the temperature of the light and the
correction applied. Some people also like to set
their white balance to “daylight” when shooting
sunsets as it will make the sunset appear warmer.
But if we were shooting with colour film your
camera wouldn’t have a white balance. Instead
you need to determine what type of light you are
shooting in, if it will produce an unwanted colour
cast and then correct it with a colour balance filter.
There are a number of ranges of these but typically
warming filter will have codes such as 81A, 81B
through to the 81EF whilst cooling filters will be in
the 80 range.
The best advice for those of you shooting digital is
not to use these filters. Much better corrections
and adjustments are available in software tools
such as Lightroom and Photoshop. Shoot in RAW
format and correct during the RAW conversion.
B&W CONTRAST FILTERS
When it comes to shooting with black and white
film, contrast filters are essential. These are
typically available in colours such as Red, Green,
Yellow and Blue and sometimes differing
strengths.
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directions by the uneven surface. But place a
polarising filter in front of the camera lens allows
you to filter the light so that it’s all travelling in the
same direction. This allows you to then see below
the surface of the water as in the example below.
But if you are a digital photographer, these
contrast filters don’t offer you any benefit and
indeed may limit your results.
Software such as Lightroom and Photoshop as well
as many black and white conversion plug-ins will
produce far superior results to using a coloured
filter. In order to gain the most from these tools
you need to work with a colour image as they
provide controls that allow you to target individual
colours in the image. If you placed a red filter in
front of your camera lens, you will produce a red
image. Try converting this to black and white and
you will lose the ability to target greens, yellows,
blues and other colours.
If you are shooting digitally, don’t use these filters.
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POLARISING FILTER
Polarising filters produce effects that are very
difficult, perhaps almost impossible to reproduce
in software.
These filters appear dark and will reduce the
amount of light passing through the lens to reach
the camera sensor. Usually they will reduce the
level of light by between 2 and 3 stops, which can
make them a good substitute for a Neutral Density
filter. I find my polarising filter very useful at
sunset, to help slow the shutter speed in order to
record movement, such as in waves.
But the true value of the polarising filter is that it
will polarise light so that all the light reaching the
camera sensor is travelling in the same direction.
By way of an example, when you look at the
surface of a lake in summer, the light reflects off it,
preventing you from seeing below the surface. This
is because the light is reflecting in different
The feature of the polarising filter that it’s
probably best known for is that it allows you to
turn a blue sky dark blue. A lesser but equally
important use of the polarising filter is when
shooting in woodland on a wet day. Under these
conditions, woodland colours can appear highly
saturated if we use a polarising filter.
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2.
Shooting into or directly away from the
sun will lessen the effect.
Polarisers have two parts although they
look like one filter. There is the part that
attaches to the lens and the front part
that rotates. You need to turn the front of
the polariser in order to adjust the
strength of the effect. As you turn the
front of the filter you will find the effect
strengthens and then lessens. It’s a good
idea to not always use the effect at
maximum strength.
Polarisers are available in two types, Linear and
Circular. Confusingly, this has nothing to do with
their shape but rather with how they work. If you
are using an autofocus camera (and most people
are), you will need to use a circular polariser.
In the example above, a polarising filter was used
to intensify the brilliant colours of the moss and
ferns whilst also slowing the exposure to
emphasise the movement in the waterfall.
Whilst polarising filters are generally easy to use,
one negative effect you might encounter is when
shooting with a wide angle lens. Here they can
cause an uneven darkening of the sky which you
might need to fix in post processing (this can be
tricky).
When using a polariser, there are two simple tips:
NEUTRAL DENSITY (ND) FILTERS
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15
1.
If you are shooting a scene where there is
directional light, such as a landscape, you
need to place the sun at a 90-degree
angle to the direction you are shooting for
the polariser to have maximum effect.
Neutral Density or ND filters as they are often
abbreviated to, reduce the amount of light
reaching the camera sensor. These filters come in
varying strengths which equate to stops of light.
They may be expressed in numbers such as 0.3,
0.6, 0.9 etc. Each of these represents a reduction in
the amount of light they allow to pass. For
example, a 0.3 ND filter will reduce the light
reaching the camera sensor by 1 stop. A 0.6 filter
reduces the light by 2 stops, a 0.9 by 3 stops etc.
Another common notation is X2, X4, X8, X16 etc.
This is referring to the effect on the exposure
duration. The X2 would double the exposure and is
therefore a reduction in the amount of light of 1
stop. The X4 would multiply the exposure time by
4 so that a 1 second exposure becomes 4 seconds.
This is the same as two stops of light being
removed. The X8 is three stops and the X16 is four
stops and so on.
When you look at these filters they will appear
dark in colour. The greater the reduction in light
they transmit, the darker they appear.
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The idea behind the ND filter is that by reducing
the light reaching the camera sensor we lengthen
the shutter speed. Each stop of light you remove
will double the duration the shutter needs to
remain open to correctly expose the image. For
example, if you have a shutter speed of 1/30”
(second) and you use a X2 ND filter, the shutter
speed will lengthen to 1/15”, assuming nothing
else changes.
There are two reasons that we might want to use a
ND filter:
1.
2.
In very bright conditions when shooting
with a wide aperture, the shutter speed
required might be beyond what the
camera can achieve. If we don’t use a ND
filter the image will be over exposed.
Where you want to achieve a slow shutter
speed to create a special effect in the
image. A typical example of this might be
blurring the movement of a waterfall.
Using these filters, it’s possible to achieve long
exposures of several seconds, even in the middle
of the day. Used in lowlight conditions, exposure
times can easily extend into minutes.
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16
“EXTREME” ND FILTERS
In recent years a new class of Neutral Density filter
has become popular. These filters are very strong,
typically reducing the light reaching the sensor by
some 6 stops or more. These filters will often
appear black due to their extreme density. You can
see an example below.
THIS IMAGE WAS CAPTURED DURING THE DAY WHEN THE CONDITIONS WERE TOO
BRIGHT TO BLUR THE MOVEMENT OF THE CASCADING WATER. IT WAS NECESSARY
TO LENGTHEN THE EXPOSURE BY AROUND 5 STOPS TO ACHIEVE THE DESIRED LEVEL
OF BLUR. AS I DIDN’T HAVE A 5 STOP ND FILTER WITH ME I USED MY 3 STOP ND
FILTER TOGETHER WITH A POLARISING FILTER.
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When exposure times extend into minutes, moving
objects can vanish completely as in the next image.
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17
This image was taken on a bright summers day. By
using a 10 stop filter together with a polarising
filter it was possible to extend the exposure time
so that the waves around the posts became a
complete blur and look like haze.
These filters are not without their problems
though. Typically, they will introduce a colour cast,
which if you are shooting colour images will need
to be corrected in post processing. In fact, the
image you see above has a strong blue appearance
which was caused by the 10 stop filter.
More recently, variable ND filters have arrived on
the market which by turning the front part of the
filter allow you to vary the strength of the light
reduction (these are in fact two polarising filters
that gradually cancel out the light as you rotate
them). Whilst most people appear to use these
filters without problem, some report poor image
quality and other problems. Treat these variable
filters with some caution and research other
people’s experiences before committing.
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NEUTRAL DENSITY GRADS
The Neutral Density Graduated filter (or ND Grad)
is half neutral density and half clear. There is a
small area of transition between the two halves
which is graduated.
the camera picks up whilst the human eye and
brain compensate.
If we were to take a picture of a landscape scene
where there is a three stop difference between the
sky and ground, either the sky will appear very
light and lacking in definition/saturation or the sky
appears fine but the ground becomes very dark.
Such images appear ugly to the viewer and it’s
definitely not how we expect to see the scene.
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The image below of the lake at sunset was shot
using a 2 stop ND Graduated filter to balance the
sky and reflection in the lake.
The ND Grad filters, like the standard ND filter, are
available in different strengths. Typically, they are
available in 1, 2, 3 and sometimes 4 stops in
strength, indicated by notations such as 0.3, 0.6,
0.9 etc. The strength refers to the strength of the
neutral density part of the filter and how much
light this will block. The purpose of these filters is
to reduce the difference in brightness between the
sky and ground in landscape scenes. In many
instances, when shooting landscapes, the sky will
be much brighter than the ground. This difference
in brightness is known as the dynamic range and it
can easily be two, three or even more stops
different. It’s this difference in dynamic range that
causes problems for the landscape photographer.
The difference in dynamic range is something that
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Below you can see an example of what can happen
when we don’t use a ND Grad filter. Notice how
the foreground is correctly exposed but the sky has
turned white and the clouds have vanished.
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The hallmark of a good landscape image is having
both the sky and ground well exposed. You can
achieve this balance by using an ND Grad where
the dark part of the filter is placed over the
brightest part of the scene, often the sky. The
graduated part of the filter is aligned over the
transition between these two areas, typically the
horizon in a landscape scene.
In the next image you can see how the entire
scene is transformed when a 2 stop ND grad is
placed over the sky. Notice how you can now see
the blue sky and definition in the clouds whilst the
hills and foreground also remain well exposed.
not the blacks, try reducing your exposure using
your cameras exposure compensation dial. If the
blacks are clipping but not the whites, try
increasing your exposure. Your camera histogram
has all the information needed to get the exposure
right.
When you first begin using ND Grad filters it can be
tempting to worry too much about using the
correct filter strength. Over the years this concern
has been heightened by magazines publishing all
sorts of advice about taking meter from the sky
and ground to work out the dynamic range. When
everyone was shooting slide film with just a few
stops of dynamic range, it was good advice. With
today’s digital cameras just forget it.
The best approach is to use the histogram on your
camera. If you’re not sure, start by using a 2 stop
ND Grad and shoot the scene. Now review the
histogram to see if you have any clipping. Clipping
occurs when areas of the scene are either too
bright or too dark (possibly both) for the camera to
cope with. If you see clipping in the highlights and
the shadows (either end of the histogram), you
may need a stronger filter. If neither are clipping
but the histogram is bunched up, then your filter
may be too strong. If the whites are clipping but
If you already have or have been looking at ND
Grad filters, you may have seen that some
manufacturers offer ½ stop filters such as a 0.45 or
0.75 filter. If you are shooting with a digital camera
in RAW format, ignore these and save your money.
A half stop difference in a filter can be more than
accommodated for in post processing if you’re
working with a RAW file. Just be sure to avoid
clipping when you shoot the scene as this means
you are losing information and detail from the
image.
One thing to avoid is trying to grad a clear blue sky.
Blue sky is typically around a midtone value and
doesn’t need to be graded. If you have clouds in
the sky, you may need to use a grad to hold the
cloud detail.
SOFT AND HARD GRADS
Most of the company’s manufacturing ND Grad
filters will produced what are known as hard and
soft grads. The term hard and soft is used to
describe to the graduated part of the filter and
how large this area is. Where there is a large
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gradient the transition is said to be soft. Where the
gradient is very small, the filter is said to be hard.
There are advantages and disadvantages to each
and each type will have its own following. A couple
of common tips that you might hear are:


Buy hard grads as they are easier to see
and line up. This is true but it’s also easier
to see these in the finished image unless
you are careful.
If you are using a smaller sensor camera
such as a Micro 43 you need hard grads
whilst for a full frame sensor you will be
better off with soft grads. There is some
logic in this but it’s actually the graduate
transition size in relation to the lens
diameter and focal length that also
matters. Additionally, if you buy smaller
sized filters, you will possibly find the
graduate transition area of the soft filter
is not too dissimilar to that of a larger
sized hard filter.
My own approach is:
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20

Use a size of filter that’s appropriate to
the size and type of camera system you
using. With a full frame or APS-C sensor
size you are probably best served by the
larger filter sizes. For my full frame
camera, I use the Lee 100mm system. For
my Micro 43 and compact cameras I use


the Lee Seven 5 series filters. I have also
successfully used the Hitech 67mm filters
with these cameras.
Where I am photographing a scene with a
clear, straight horizon I like to use a hard
graduate filter. If the horizon isn’t
straight or has an important feature
above the horizon line I will use a soft
filter. This can make later post processing
easier as you may need to correct dark
areas which couldn’t be avoided with the
filter.
If I need to stack multiple filters for a
stronger effect, I will try to pair a soft and
hard grad filter together. Typically, I will
try to use a soft grad for the stronger of
the two filters as this makes for a more
natural blend that’s harder to detect in
the final image.
REVERSE ND GRADS
Recently, a new class of ND Grad has arrived and
that is the Reverse ND Grad. These filters are
similar in construction and strength to the
standard ND Grad. The difference between the
two can be seen along the area of transition. In
this area the graduate is actually stronger than the
top area of the filter. You can see an example
below. Notice how the area near to the transition
is slightly darker than the top part of the grad.
These filters tend to be used where the sun is very
close to the horizon and therefore brighter near to
the transition area. Reverse ND Grads prevent the
area higher in the sky from becoming too dark.
Don’t worry if you can’t afford these grads (they
are expensive) and any problems caused by using
standard ND Grads can be easily corrected in
Lightroom.
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INFRARED
There are really two types of infrared filter; those
that allow visible light through whilst blocking
infrared light and those that block visible light
whilst allowing infrared light to pass.
Typically, these filters are used with cameras that
have been modified in some way to shoot infrared
photographs. To better understand this, we need
to know a little more about how the cameras are
modified.
Digital camera sensors are sensitive to both visible
and infrared (invisible) light and will record an
image for both. What determines if light is infrared
or not is its wavelength. The wavelength of light is
measured in a unit called a Newton Meter or nm. A
wavelength between 400nm and 700nm is visible
whilst above 700nm the light turns infrared and is
invisible to humans.
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Digital cameras are fitted with filters that block the
infrared light whilst allowing visible light to pass.
This is to help maintain image sharpness as
infrared light focusses differently to visible light. If
you have both types of light creating your image,
one might be focussed differently to the other, so
causing a soft image.
When a camera is converted to shoot infrared, the
infrared blocking filter is removed. It is possible to
replace the filter with a clear glass filter. This is
known as a full spectrum conversion as it allows all
wavelengths of light (visible and infrared) to reach
the sensor.
Alternatively, the infrared blocking filter could be
replaced by a filter that blocks visible light but
allows infrared light to pass. This is a common
infrared conversion approach. The new filter that’s
attached to the sensor is available in a number of
different strengths such as 680nm, 720nm, 850nm
etc. These strengths describe the wavelength
below which light is blocked.
For example, a 720nm
filter will block all
light below 720nm
but allow light with a
wavelength above
this (infrared) to pass.
The image recorded
by the camera sensor
is then purely infrared
light which can have
some rather surreal
characteristics.
You can see an
example of a black
and white infrared
image on this page.
Notice how the leaves
and plants have
turned white. This is
due to them reflect infrared light to avoid damage,
an effect called the Wood Effect. Notice also how
dark the water is, as it tends to absorb rather than
reflect infrared light.
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Typically, the infrared filters you buy are the
screw-in type that can be attached to the camera
lens. These can be used with cameras that have a
full spectrum conversion or have an infrared filter
with a lower rating than the filter you are using.
For example, I have an infrared camera which has
been converted using a 720nm filter. This blocks all
light with a wavelength of less than 720nm so I can
attach an 850nm filter to the lens for an even more
intense infrared effect.
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It is possible to use infrared filters with digital
cameras that haven’t been converted to shoot
infrared. How well this works will depend on the
strength of the infrared blocking filter in the
camera. For example, when I attach a 720nm filter
to my Olympus EM5, I can still capture images but
the exposure is typically in the region of 5-30
seconds, but could be much longer depending on
conditions and camera settings. If I switch the
720nm filter for an 850nm filter, I can’t record an
image at all, no matter how long the exposure. All
light is now being blocked from reaching the
sensor by the combination of filters.
Whether you can record an image with an Infrared
filter attached to your camera will depend on the
make and model of camera. Older and cheaper
cameras tend to have weaker, less effective
blocking filters and are therefore better for this
purpose. If you do find that you are able to record
an image with an infrared filter in place, it’s likely
that the exposure will be a long one, requiring a
tripod.
You can test your camera for possible infrared
sensitivity by placing it in live view and seeing if
you can see the light emitted from a TV remote. If
your camera can see this, then it is recording the
infrared light used by the remote and probably has
quite a weak blocking filter.
If you decide to purchase and try using infrared
filters with your camera, don’t spend a lot of
money. It’s now possible to buy quite acceptable
filters very cheaply from eBay and Amazon. I have
purchased a few of these now and testing them
with my infrared camera, all worked fine.
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CLEANING FILTERS
At some point, it’s inevitable that your filters will
become dirty. You might place a greasy finger print
on them, drop them in the mud or they simply get
covered in sea spray when you use them at the
beach. I have experienced all these and often need
to give my filters a good clean. Here’s how I do it.
For screw in filters I use lens cleaner and lens
cleaning papers. If I can, I leave the filter in place
on the lens whilst I clean it. After all, my
UV/protector filters are often in place permanently
so only one side gets dirty. If I do need to clean
both sides I will remove the filter and then allow it
to air dry before replacing it on the lens. Good lens
cleaning fluid will evaporate quickly but give it
plenty of time so as to avoid the risk of
condensation between the filter and lens.
Condensation behind a filter can easily fog your
photographs.
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For the square filters I don’t bother with the lens
fluid. I did use this approach at one time but found
that it often left the filters greasy. I now use
washing up liquid or if that’s not available, soap.
Before you start be sure to wash your hands so
that they are very clean. Wet the filter under a
running tap and then rub plenty of soap onto your
hands. Next rub the soap on your hands over the
surface of the filter. Be sure to cover the entire
surface on both sides and give the filter a good
rub.
When you’re happy the filter has been cleaned,
run the filter under the tap to wash off the soap.
You may also need to rub the filter a little to help
remove the soap. As you do this you should notice
that water begins to run off the surface of the
filter, leaving it almost dry. You might also hear the
filter squeaking a little if you are rubbing it
between your fingers. Finally, carefully dry the
filter on a clean soft towel and replace it back in its
storage case or your filter wallet.
I have found this method to be by far the quickest,
cheapest and most effective for cleaning square
filters.
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SUMMARY
2.
To finish this guide I would like to leave you with
some questions so that you can develop a plan of
action:
3.
24
1.
Page
Think about the photography that you
have created over the past couple of
years. How could you have improved by
using filters or using them differently?
4.
5.
Think about the photography you would
like to create in the future. How could
filters help you?
From your first two answers, what filters
(and types of filter) do you need to buy or
replace?
What accessories do you need to better
use your filters?
How do you need to change your
photography to make full use of your
filters? How will you make these changes?
If I can leave you with one final piece of advice, it’s
that filters are not an optional accessory. Filters
are an essential part of Landscape Photography.
You need to have the right tools as well as be able
to use these without giving it a second thought.
Good luck and enjoy your photography.

The Landscape Photographers Guide to Filters

Transcription

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