PhotoPlus The Canon Magazine – August 2019

ND Filter kNowleDge

The Canon Magazine 83

D filters are available
in both standard
circular screw-on
flavour or as a slide-in
option for a square filter
system. Circular and square
filters each have their pros and
cons, but square ones have the
advantage when it comes to
long exposure work with
strong ND filters.

For a start, you can

compose and focus shots

without the filter in place, then

quickly slide it into position. Of

course, if you use the Live View

display you can size up the shot

with a strong ND already

attached to the lens, but this

will drain the camera’s battery

• and you’ll need all the juice
  you can get when shooting

extended exposures.

A square system also

makes it easier to combine an

ND with other filters, such as a

graduated ND filter or a

polarizer, or if you want to

quickly upgrade or downgrade

to a different ND strength.

The chief drawback to a

square filter system is its bulk:

you’ll need an adapter for each

of the different

sized filter threads in your lens

collection, plus the filter holder

and the fragile glass filters

themselves, along their

suitably robust protection.

That can take up more room in

your bag than a small selection

of screw-on filters.

The filTer adaptor rings
of square systems can
prevent you from attaching
the original cap on the lens

• having to remove the ring
  each time you want to put
  the lens away quickly gets
  tedious. You can, thankfully,
  buy specific plastic caps
  designed to fit those larger
  adaptor rings.

ND filter know-how

Protect your lens

Learn how to get your camera and filters ready for action

Consider using larger caps if you go square

N

Filter holDer

Square filter systems have two bits:
an adaptor ring (screwed onto the
lens) and a filter holder, which is
clipped or screwed onto this ring. So
you only need one filter holder and a
single set of filters to use them on all
kinds of lenses. Brands include LEE
Filters, Formatt-Hitech and NiSi.

Filter slots

Filter holders mostly have three slots

and in most cases you’ll need to slide

the ND filter into the slot nearest the

lens. You can use other filters in the

remaining slots. If you’re using an

ultra-wide lens you may notice the

edge of the filter system in your shot,

so be prepared to zoom in a little.

eyepiece cover

Stray light can enter the viewfinder of

a DSLR, even when using Live View,

so it’s worth blocking the eyepiece to

prevent patches of light. Remove the

eyecup by squeezing the sides and

lifting up, then slide the eyepiece

cover attached to Canon’s camera

straps onto the eyecup holder.

Variable ND filters

As well as the standard ND filter,

there are also ‘variable’ versions.

These are two-part circular filters

similar to polarizers, with the front

half being rotated to increase or

decrease the density. Variable NDs

are more popular with filmmakers,

who use them to correct the shutter

speed when moving from indoor to

outdoor locations, but they do suffer

a dark ‘X’ effect when they are used

at their densest settings.

Do you need a grad?

ND filters also come in a graduated

form, which has separate dark and

clear parts. By positioning the filter

so that the dark part covers a bright

sky and the clear part lines up with

the land, you can reduce the contrast

and record detail in both. You could

do away with the filter and make

individual exposures for the sky and

the land, then blend them digitally,

but when it comes to long exposures

it’s quicker to do it in a single take.

light-tight seAl

Very strong ND filters usually come

with a foam gasket around the edge

in order to prevent unwanted light

leaking in during a long exposure.

Adjust the height of the filter in the

slot until you can see the gasket is

making a tight seal with the holder

at each of the corners.