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8/10/2019 Tips - Optical Filters
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Back in the days of film, youd have
to use optical filters for a variety of
reasons. In addition to protecting a
lens against the elements and providingsome protection against knocks, filters
were used to correct the colour balance of
film for example to add a warm orange tint
or a cool blue one to record a neutral result
under different lighting, depending on the
film stock you were using. Digital cameras
dont need this type of filtration, as their
white balance control enables you to
neutralise any colour cast on the fly.
In the days before Photoshop, youd
often have to resort to using filters to
achieve certain effects in-camera too, such
as a soft focus filter to add a hazy look or a
graduated tobacco filter to artificially boost
a sunset. These days theres no need to try
and achieve an effect like this in-camera;
you can do it all post-shoot using digital
filters, adjustment layers and other tools.
So, the only reason you still need to fit
You can go some way towards reproducing
the latter effect in Photoshop, but as for
reducing glare and removing reflections
well, itll take hours of painstaking work,
if you can reproduce the effect at all.
There are some downsides to using
a polarising filter. For a start, theyre not
cheap. In fact, a polariser will certainly be the
Is there any po nt n us ngoptical filters on lenses?Learn why theres stilla place for lens filtersin your camera bag
Youcanreplicatetheeffectsof
polarisersandNDgradfiltersin
Photoshopbutyoullneedan
NDfilte
rforextendingexposurestocreatesilkyskiesan
dseas!
8/10/2019 Tips - Optical Filters
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A polariser willcertainly be themost expensive filter
you buy, this side ofa LEE Big Stopper
Real vs fake:Graduated ND filtersWhy ND grad?Without an ND grad, the contrast between
the landscape and the sky may be too great
for the camera to record detail in both areas
in a single exposure. Expose for the land, and
the sky may be overexposed and featureless;
take a shot with the sky exposed correctly
and the landscape may be underexposed.
A neutral density graduated
filter enables you to record
detail in both a bright sky
and a darker foreground.Position the clear part of
the filter over the land and
the darker part over the sky,
and you bring the exposure
of the two areas closertogether, within the
dynamic range of the
cameras sensor. Arguably,
these days theres less of a
need for these filters, as you
can tackle exposuredifferences when you
process your images. If the
exposure difference
is relatively small, you can
darken the sky or lighten
the landscape with an
adjustment layer, and
then mask the effect as
required. If the exposuredifference is more extreme,
then shooting two or more
bracketed exposures with
a tripod-mounted camera
will enable you to blend
the images to capture an
expanded brightness range.
REALNDGRAD
FAKENDGRAD
Sky appears too bright
Land exposed correctly
Sky exposed correctly
Land appears too dark
biggest lens diameter you own, and use
step-up rings to fit it to your smaller lenses.
Polarisers also cut the amount of light
entering the lens, by approximately two
stops when fully polarised. This can lead to
slower shutter speeds, increasing the risk of
motion blur or camera shake; one way to
compensate for this is to increase the ISO.If youwantto capture the effects of
motion blur, a standard ND filter is often the
way to go in bright conditions. These are
a solid neutral grey, and are used to simply
cut the amount of light entering the lens.
Theyre available in a range of strengths,
each rated for the number of stops or
exposure values they reduce the light by.
So a three-stop ND (sometimes called a 0.9
ND or an ND8) enables you to reduce theshutter speed by three stops; for example,
you could use a shutter speed of 1/15 sec
8/10/2019 Tips - Optical Filters
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Its relatively straightforward to emulate the effects
of ND grads in Photoshop, Elements or Lightroom,
but doing the same for a polarising filter is more
challenging. To boost the contrast between a blue
sky and white clouds in a similar way to a polariser,
shoot in Raw and process your files in Lightroom/
Photoshop ACR. Select the Blue slider under the
Lightness tab of the HSL panel, and drag it left to
darken the sky. The giveaway that a polariser hasnt
been used is the reflections in the windows; theyrestill present in the digital fake. Recreating the effect
of an ND filter on moving clouds is easier: select the
sky in Photoshop, then apply the Motion Blur filter.
Real vs fake: NDfilters & polarisers
Digital filterdrawbacksAlthough you can resolve exposure
issues and recreate the effects of some
filters in software, doing it digitally brings
its own problems. For a start, you can
only work with what youve recorded.
If the highlights in the sky were severely
overexposed at the point of capture,
you wont be able to bring them back
with a digital grad. As you can see in
th i b l t f d k
While using filters at the time of shooting
can mean less time spent in front of the
computer, and is arguably more enjoyable,
you will face a few problems. If you attach
a filter to an ultra-wide angle lens, you may
see it in the corners of your shots; this
problem is exacerbated on full-frame
cameras, or if you stack more than onefilter, and youll have to either zoom in a
little, crop the shot or choose thinner
filters. If youre not careful when you
Optical filter pitfalls
REALPOLARISINGFILTER FAKEPOLARISI
NGFILTER
Fit a thick polariser to a 17mm lens on a
full-frame 5D and this is what youll see!
8/10/2019 Tips - Optical Filters
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to exaggerate movement where youd
normally use 1/125 sec. Faking a long
exposure effect in Photoshop wontalways look as natural as the real thing.
Its fairly easy to select the sky and apply
a blur filter to clouds, but adding motion
blur effects to water, foliage and other
objects is slightly trickier.
If you want to balance the exposure of
a landscape and bright sky, tradition has it
that youd reach for a graduated ND filter.
However, you can achieve the same effect
by capturing one exposure for the sky and
another for the landscape, and blending
them with layer masks or HDR software.
This option is useful when areas of the
scene would cross the boundary wherethe dark and clear parts of the filter meet,
such as in cityscapes or a coastline with
cliffs; if you used an ND grad youd darken
parts of the landscape, as well as the sky.
That aside, theres a lot to be said for
getting it right in-camera. Spending a few
more minutes fitting filters and working
out exposure settings may save you time
at the editing stage and the satisfaction
that comes from doing it hands-on
shouldnt be overlooked either!
Xxxxx
Colour castsSome optical filters can create a colour
cast, leaving images looking a little pink
or too warm. To counter this, you could
try using your cameras White Balance
Correction option in the red shooting
menu to tweak the amount of blue,
amber, green and magenta; however,
wed recommend shooting Raw so that
you can do this when you process the
image. Strong ND filters can leave images
with a heavy blue cast, so dial in a Kelvin
white balance value of 7000K or more.
REAL10-STOPNDFILTER
FAKENDFILTER
UNCORRECTED10-STOPNDFILTER
CORRECTED10-STOPNDFILTER
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