1
What is a fast lens?
The term ‘fast’ has nothing to do
with the how quick the lens is at
focusing or whether it’s used for
action photography. In this sense,
the word refers to the maximum
aperture that lens can shoot at.
A typical ‘fast’ lens will have an
aperture of f/1.4, f/1.8 or f/2.8;
this allows a lot of light in so that
faster shutter speeds are possible,
hence the phrase ‘fast lens’.2
When would a fast lens
be useful?
Thanks to their wide maximum
apertures, fast lenses are great in
low-light situations, enabling you
to get faster shutter speeds even
in relatively dark conditions. They
are also great for subjects likeportraiture, where limited
sharpness can be used creatively,
to make sure the subject is nicely
separated from the background.3
How do I know if my lens is fast?
All lenses have their aperture range
written on them, so if you’re not
sure just look and see whether you
can read any of the wide apertures
(f/1.4 to f/2.8) printed on yours.
If you can’t find a label on the
lens, select Aperture Priority
and run through the
available apertures.4
Are there any
disadvantages
to a fast lens?
In terms of performance
and creativity, fastlenses are really useful and a
desirable thing to have in your
camera bag. The biggest
disadvantage is that they are
expensive to buy, and they are
also heavier to carry. Fast lenses
are more often fixed-focal-length
lenses, known as primes, but
some zoom lenses are also
fast through their range.Tech Check
‘Fast’ lenses
http://www.digitalcameraworld.com APRIL 2020 DIGITAL CAMERA^99
Wild about backgrounds
Q
I am really
starting to get
into wildlifephotography, but I’m
struggling to make my
subjects stand out from
the background. Can
you give me any advice
on how to do this?
Tina Morris
A
I could probably write a
book on this, Tina, but
there are lots of simple
things you can think
about when you are out in the field.
In one sense, it’s as simple as
thinking about the relationship
between your subject and the
environment they are in. If you are
shooting with a telephoto lens and
able to get low, you can try to separate
subject and background through
depth of field. The further away your
background is, the more it will fall out
of focus, and the diffusion will create
a natural frame for the subject. If you
are shooting from a higher position
(standing) and shooting down on a
smaller subject, the ground is your
backdrop, and because it’s close
behind the animal, it can still be
relatively sharp. Other things to
consider include looking for darker
backgrounds to place a bright subject
against – and vice versa, of course.
My shot of a flamingo is a perfect
example of what I am talking about
here. I’ve been able to isolate the main
subject by photographing it from a
very low viewpoint so the background
is a long way away. I’ve also used a
long lens set to an aperture of f/4 to
limit depth of field, while the contrast
of the brighter feathers illuminated in
the evening light against the darker
backdrop means the subject really
pops out. You won’t necessarily be
able to adopt all these techniques
in every image, but one or two of
them each time will certainly
make a difference.A ‘fast’ lens is one that enables
you to set a wide aperture – ideal
for portraits, for example.A combination of
techniques makes it
simple to separate
wildlife from
their habitat.