Shutter
Speed Priority – A Beginner’s Guide
In this, the second of
my beginner’s guides, I explain the principles of Shutter Speed
Priority mode, marked as “S” for Shutter or sometimes “TV”
for Time Value, on the camera’s mode dial. Whether you use a film
camera or a digital camera, the basic principles are the same but for
the purposes of this article I will presume the use of a digital
camera of either the single lens reflex type or the non-reflex type.
The shutter speed is
the duration of time that the light is allowed to strike the sensor,
controlled in fractions of a second, each progressive setting giving
half (or double) the duration of the previous setting. Here is the
shutter speed progression table in one EV steps: 1/15 - 1/30 - 1/60
- 1.125 - 1/250 - 1/500 - 1/1000 - 1/2000 - 1/4000 – 1/8000 etc.
The shutter duration setting may also, as has been pointed out in a
reply to my previous article, also extend to whole seconds, minutes
or even hours, depending on the circumstances.
The "aperture"
is the "f" stop or "f" number. It is the opening
in the iris diaphragm in the lens and controls the intensity of light
(or the brightness of the image) passing through the lens to the
sensor. Each progressive f number allows double (or half) the amount
of light to pass through the lens. Here is the table of progressive
f numbers:
f/0.7 - f/1.0 - f/1.4 -
f2.0 - f2.8 - f/4.0 - f/5.6 - f/8 - f/11 - f/16 - f/22 - f/32 - f/45
- f/64 etc.
I had taken the train
into London Town one afternoon and found myself in the vicinity of
Petticoat Lane. Being a nice sunny autumn day I was equipped with my
“street” kit, which is a Nikon D7000 body fitted with an AF
Nikkor 35mm f1.8G prime lens. I prefer this combination for
street photography because it is very lightweight, small and
unobtrusive. On my APS-crop sensor camera the 35mm focal length
gives the equivalent field of view of a 52.5mm lens on a full frame
camera which is near enough to 50mm as to make no difference and
suits my style of street photography very well.
I always keep a lookout
for colorful buildings or good street graffiti and I happened to
come upon a restaurant with very colorful security shutters over the
windows. Being mid-afternoon, the place was not yet open for
business and the shutters were still pulled down. They were painted
to resemble market stalls, and each of the four was a different,
vibrant, colour. Even better, the building opposite had stone
stairs going up to its entrance doors which allowed me a good vantage
point to photograph the restaurant window shutters. While I was
contemplating the scene, I noticed that there was a cycle lane
running past the restaurant along which a steady stream of cyclists
passed. Most cyclists in London wear high-visibility jackets and
helmets, and the strident colours of these jackets were contrasting
wonderfully with the bright colours of the shutters. I wanted to use
the cyclists as part of my composition and at the same time convey
the movement of the cyclists across the scene.
To do so I would have
to introduce a certain amount of blur or “subject movement”
to the cyclists, in the direction of their travel. I would have to
keep the restaurant facade and the rest of the scene pin sharp. I
had no idea how fast the cyclists were actually travelling, I did not
have a tripod, there was no convenient mailbox or lamp-post to rest
my camera on, therefore some experimentation was in order. I set
the ISO to 200, which is my personal “default” setting for
colour, street shooting. I’m sure that the Nikon D7000 is
capable of virtually noiseless images at higher sensitivity settings,
but this was November 2011 and I had not had the camera long enough
to be sure. I have one rule when out with a camera – never
“presume.” I also had a nice big print in mind, and I wanted it
to be as good as possible. I set the mode to “S” for Shutter
Speed Priority which would enable me to select a suitably slow
shutter speed to show subject movement in the bicycles. The question
was, how slow a shutter speed could I set without sacrificing
sharpness in the rest of the scene?
There is no VR or IS
(image stabilization) feature in the Nikon 35mm f1.8G lens, nor is
there in the camera body, so to give the camera some stability I sat
on the steps opposite and rested my elbows on my knees. I chose a
height on the steps that gave me a viewpoint parallel to the building
opposite. This meant that I could keep my camera as parallel to the
ground as possible resulting in minimal perspective distortion. I
focussed on the facade of the building opposite and composed the
image. There was a traffic sign on poles in the middle of the scene
that was quite distracting, so if possible I needed to place a
cyclist in front of the poles to “hide” them as much as possible.
I included the doors of the restaurant on either side and a strip of
the grey tarmac road in the foreground to act as a neutral foil to
the bright colours of the window shutters. I quite liked the magenta
traffic lane markings that matched the colour of the window second
from the right. I decided to try a shutter speed of 1/60th
at which speed the camera selected an aperture of f/12 with the
metering set to center weighted. This wasn't going to be easy!
It was a case of
waiting for a cyclist to come by while holding the camera perfectly
still and trying again and again to get the shot! If I had panned
the camera (followed the cyclist) I would have had a sharp cyclist
and a blurry background. I wanted the opposite, a sharp background
and a blurry cyclist. After half a dozen or so attempts I decided to
increase the shutter speed to 1/90th, just to compare the
difference in subject movement blur, and that was when I managed to
release the shutter at the “definitive moment” when one cyclist
came past, dressed in hi-viz jacket, and travelling at quite a rapid
rate, and I captured him perfectly in front of the traffic sign
poles. The exposure was 1/90th at f9.5, ISO 200, focus
mode AF-A , 3D tracking, back button focusing. I could have used
manual focus, but back button focusing has the same effect, as the
focus will not move once I release the button and this is my default
focus method.
I had the Jpg image
quality set to large Jpg normal, picture control Vivid with
saturation +3 because I wanted the colours to “pop.” I
downloaded into Lightroom in my usual way (see this previous post: http://grahams-word.blogspot.co.uk/2013/09/pasm-which-to-use-tutorial.html ) I opened the Jpg image in Photoshop CS5, created and saved a
master Tiff file, re-sized it to 1024 pixels across, converted the
colour space to sRGB, sharpened it for the web, applied my watermark,
saved it as a 96dpi Jpg file at quality setting 6 and that’s the
image you see here. I did not use the RAW file as there was no need.
Shutter speed priority
comes into play whenever subject motion has to be either frozen or
shown as a motion blur. When photographing soccer on a bright
day with a 70-300mm lens, (that’s the game where everybody runs
around chasing a big round ball and tries to kick it between the
opposing team’s goal posts) I set the mode to “S” for “Shutter
Priority” , I set a shutter speed of 1/2000th and ISO to
400. Thus the camera selects an aperture of around f/8 which
results in sufficient depth of field to get the players sharp while
isolating them somewhat from the background. The shutter speed of
1/2000th is fast enough to freeze the
action.
When photographing
birds in flight (or BIF as I have been educated into calling it)
shutter speed priority is a must in order to freeze the bird in
flight. Depending on the speed of the bird, the distance and my
panning ability, I set a shutter speed of between 1/500th
and 1/2000th with ISO on 200 auto and plus one EV
compensation if I am shooting against the bright sky. I will not go
into all of the other parameters of BIF photography here.
Another subject that
requires shutter priority mode is motor sport. Photographing racing
motorcycles or racing cars from the track-side requires a good
understanding of shutter priority mode and a practised skill in being
able to pan the camera to maintain a rapidly moving subject in the
correct place within the frame to make a pleasing composition. Good
panning technique will “absorb” the motion of the subject to a
certain degree, and the slower the shutter speed, the more the
background will blur. Choosing a shutter speed that results in a
nicely blurred background while keeping the subject pin sharp while
you pan the camera, is a learned skill, but once learned, can result
in spectacular photographs.
Remember the exposure
triangle – 1) Aperture, 2) Shutter speed and 3) ISO sensitivity.
To maintain equality, If you adjust any one of them, one other must
be adjusted accordingly to compensate.
FAQ:
Shutter release mode:
Why didn't I set the
camera on multi-shot, burst mode and just hold down the shutter
release while a cyclist came by? Well, I could have, but what
would have been the challenge in that? Besides, I’m “old school”
and I resent the fact that the camera can probably out-think me at
every turn. Using single shot, I had to compensate for the shutter
lag (the delay between pressing the shutter release and the shutter
actually firing) which is always good training.
Why did I use center weighted metering?
I could have used
matrix metering, but I find that I get more consistent results using
center weighted metering with the Nikon D7k. In matrix metering
mode, the metering uses not only the brightness of the various parts
of the scene, but also the brightness and colour of the
subject identified by the auto-focus point. I used back button
focusing, single point 3-D tracking, therefore, in matrix metering
mode, the colour and brightness of whatever was under the center
focusing point at the instant that I pressed the “focus on”
button would have influenced the exposure. I personally don’t like
this feature as I think that it introduces a degree of inconsistency
to the matrix metering. Just my opinion.
Picture control – picture style:
Why did I use “Vivid”
picture setting with additional boost of saturation? I wanted the
colours of the window shutters as well as the high-vis jackets of the
cyclists to really “pop” against the fairly dull background. The
default “Vivid” setting on the Nikon D7k isn’t vivid enough for
the result that I envisaged. I also had the RAW file to play with if
I didn't get what I wanted from the Jpg. As it turned out, the Jpg
file was right on the button. Incidentally, I don’t think that
this image would have worked in monochrome (B&W) at all.
Graham Serretta
London 2013.
