ISO 400, S/SPEED 1/200, APERTURE f. 25 , FOCAL LENGTH 25 MM.
Friday 16 August 2013
Sunday 14 April 2013
UNDERSTANDING THE ISO
The sensitiveness of the sensor to light
is also known as ISO. In order to understand this better think of
walking from a bright lighted room straight into a room with hardly any
light at all, or a dark room. Once you walk in, your eyes won’t be able
to see a thing. Give it a few minutes and your eyes will adjust to the
darkness and you will start to see your surroundings. Your eyes
automatically compensate for the lack of light by increasing the
sensitivity (ISO) of retina (sensor) or increasing the diameter of Irish
(aperture). Camera does the same thing with ISO with the help of Aperture & Shutter Speed.
In the days of film cameras users would
load films of different speeds (ISO) depending on the lighting condition
in which they would be shooting pictures. If they would be shooting in
low light conditions, they would load the camera with a high ISO film
and vice versa. When digital cameras replaced the film cameras of
yesteryears, the concept of ISO remained the same but the films were
replaced with electronic sensors. Still today, camera manufacturers
refer to the sensitivity of the sensor with the term ISO. If you check
the specifications of a DSLR for example, you would find details such as
ISO 100 – 6400. What it means is basically that the sensor is able to
shoot images in a range of 100 – 6400. It can range from 25 to 256000.
Higher the ISO number, higher the sensitivity. Usually ISO 50-400 is
considered low ISO. ISO 800 and up are considered highISO. They both
have their advantages & disadvantages.
ISO Menu
High ISO
High ISO lets you take photographs at
locations where there is a lack of light & higher shutter speed is
required to freeze the action. For example in indoor sport or wedding
ceremony where even widest aperture is not enough to provide sufficient
light for a shutter speed to freeze the action. In that situations,
camera compensates for the lack of light by increasing the ISO. Now, in
low light situations, you could use a flash, but if you don’t have one
or you don’t like the effect of artificial light or in certain places
where Flash are prohibited you can move to a higher ISO.
You should remember that although a
higher ISO setting will let you get a correct exposure even with a poor
light source, you will also get more digital noise. Digital noise is the
small squares that you can sometimes see on photographs. Usually
cameras (both DSLR and Point & Shoot) face an issue of noise when
shooting pictures at high ISO levels. This happens because the filter
array of red, blue and green are unable to properly identify the correct
colors in the light waves and thus dark spots appear on the final
picture. With a low ISO setting, you will hardly or not even see those
squares, but with a high ISO setting, those squares are visible.
Fortunately modern DSLR like High end Canon 1DX, 5D mark III) or Nikon
D4, D700, D800 can handle noise very well and capable to produce clean
images even at 3200 ISO.
Low ISO
On the other hand the lower ISO setting
is generally used when there is lot of light around the subject or the
subject is well illuminated or most importantly when more details with
less noise is required. For example portrait & landscape photography
the ISO setting is deliberately reduced to something 100 or less to
produce more details.
However, a low ISO setting is also a
cause for camera shake if you are holding the camera. It is not because
of lower ISO, but usually for longer shutter speed. Because in low ISO
setting sensor needs more time (longer shutter speed) to absorb light.
With a slow shutter speed, the subject can move or your camera can move
while the shot is being taken and you will end up with a blurred photo.
Now you have two options, use external light source (Flash) or a Tripod.
You will need a bit of practice when
using ISO. Take several photographs of the same subject, under the same
light conditions, with different ISO settings. Keep a note of the
sequence of ISO settings you used so when you view your photographs on a
large screen, you can identify how these different ISO settings
affected your photograph.
WHAT IS SHUTTER SPEED
Before it reaches the camera’s sensor,
the light has to travel through some basic camera structures. First, it
has to pass through the lens elements, then the aperture
and lastly the shutter. Lens elements can’t block the light. Because
they are made of clear glasses. Aperture can block the flow of light
partially by increasing and decreasing the diameter of the opening. Only
Shutter can block the light flow completely.
What is shutter?
Shutter is like a time keeper or stop
watch of a camera. It controls flow of light by opening & closing
it. It follows the same principles of window shutter. When it is open it
allows the the light to pass through it & no light can pass through
a closed shutter.
Shutter speed
It is the time between opening &
closure of the shutter. shutter speed is expressed in seconds. It
determines the length of time the shutter remains open to allow the
light to pass through the lens aperture and expose the image sensor.
For example a shutter speed of 1/30th of a second is slower than a shutter speed of 1/250th of a second. This is used in tandem with the ISO setting and the Aperture. When
using a wider aperture a faster shutter speed is recommended to avoid
over exposure. A faster shutter speed is recommended when shooting fast
action photography or even sports photography when it is intended to
‘freeze’ the action. A slower shutter speed is used when special effects
such as motion blur, light trails or water blur is required to be shot.
Faster shutter speeds are suitable when
the camera is hand held. Comparatively when the camera is mounted on a
tripod a slower shutter speed is feasible and manageable. Creative
photographers use slower shutter speeds along with a low ISO, wide
aperture (in manual mode) and a Graduated neutral density filter to capture water trails or even motion blur in broad day light.
DEPTH OF FIELD
Depth of field is usually described as
the amount of the frame that is in sharp focus. When we look at a scene
with our naked eye almost everything appears sharp. But that is not the
case when we compose the same scene with cameras. Some part of it is
blurred out. The more the frame is in sharp focus, the more is the depth
of field and vice versa.
Depth of field (DOF) depends on two factors: aperture and distance of the subject from camera (magnification). Wider aperture and closer subject give the shallower DOF.
There is an inverse relationship between
the aperture of your lens and the depth of field. Narrower is the
aperture more is the depth of field. Usually when you set your lens to
f/1.2 or f/1.4 (in a prime lens) or f/2.8 (in a zoom lens) a soft blur
is created around the back and front of the subject. This is also known
as bokeh.
When this happens only a small part of the frame (depending on where
you’re focusing) is n sharp focus and the rest is blurred out.
When you reduce the aperture the whole
frame starts to get into sharp focus. The narrower the aperture the
sharper is the image. As you move from of f/4 or f/5.6 all the way to
f/11 and beyond the images get sharper and sharper. The reason is the
light rays reflected against the subject and passing through the
aperture gets refracted by the front element of the lens and meets the
sensor at a precise point creating a sharp image. Narrower the aperture
more precise is this meeting of light creating a sharper image and thus
bigger depth of field.
Depth of field also depends upon the
kind of lens that you use. A wide angle prime lens offers more soft blur
because it has a wider aperture. But if you stop down to f/8 and even
narrower, a large depth of field can be created. A wide angle lens
reduces the perspective of the subject as it fits in more inside the
frame; also know as field of view. As such a hut on the beach will
appear smaller than the actual real life size when the picture is
finally taken. On the other tele lenses have an effect of increasing the
size of the subject on the final image. The higher magnification allows
you to capture more detail of the subject but also reduce the field of
view and the depth of field.
Basic tips to play around with depth of field
Set your aperture to a minimum of f/8 to
make sure you have a good platform to start with. Always ensure that
you zoom out and exploit the widest limits of your lens, even if you’re
using a tele lens. Tele lenses have a narrow maximum aperture so once
you have zoomed out completely you may still have an aperture of f/4 to
start off. Wide angle lenses can pack in a lot provided you can start at
f/8 or even narrower. When shooting landscape or any other subject,
never focus on the infinity. Always focus on something closer so that
you have a sharp depth of field behind the point where you’re focusing.
HOW APERTURE WORKS
What is Aperture?
Aperture is a diaphragm like openig
inside the lens which diameter is adjustable. By adjusting the diameter
of the opening it controls the amount of light that passing through the
lens and hits the camera sensor. However that needs to be balanced with a correct ISO setting (say ISO 100) and the right Shutter speed to get proper Exposure.
Usually when a photographer sets the camera on aperture priority mode,
the shutter speed and the ISO settings are auto adjusted by the camera.
Aperture is measured in F stops. Usually
when you read the specifications of a lens you will notice a
specification f/1.2, f/1.4, f/1.8, f/2, f/2.4, f/2.8, f/4 and so on.
This is the measurement of the maximum opening of the lens. The more the
number following the letter F, the narrower is the aperture (this is a
bit confusing). Wider the aperture the more light it can take in and
that means the less time the camera lens needs to remain open. As such
wider the maximum aperture faster is the lens. When one shifts from one
f/1.2 to f/1.4 or so on, the aperture of the lens is reduced by a factor
of 2. The shutter speed as such needs to be increased by a factor of 2
to match the lack of light entering the lens. As such increasing one and
reducing the other or vice versa will have the same effect.
Both wider and narrower apertures have
their own advantages. The former is used to create a soft blur around
the focus point (or the subject) which is also known as bokeh and the
later is used for increasing Depth of Field and is generally used for the purpose of landscape photography.
Here are a few things to remember:Smaller f number = bigger opening = more light in sensor = shallow Depth of Field
Larger f number = smaller opening = less light in sensor = deep Depth of field
There are several things you can
accomplish by manually adjusting fstop. You can choose what “depth of
field” you want by adjusting fstop. Depth of field
means the amount of focus you want in your photograph. A photo with a
“deep” depth of field means that the whole photo is focused. A photo
with a “shallow” depth of field means that only a certain area of the
photo is focused and the other areas are sort of blurred.
If you want your viewers to focus on a
certain object in your photograph, you would choose a shallow depth of
field because the object will be focused and the background will be
blurry. This will force the viewer to focus on your object.
If you want your viewer to focus on the
whole photo, you would need a deep depth of field. Nothing on the photo
is blurred. Everything will be focused. This is great if you’re taking a
picture of the landscape and you want your viewer to appreciate
everything in your photo.
Take your time to discover the different
aperture settings your camera has. The more you practice, the more
control you will have over your camera.
BASIC OF PHOTOGRAPHY
The key to all photographs, whether
shooting with film or digital cameras, is light. It will determine how
will you compensate or balance the exposure. The rule is simple. If
there is too much light you have to reduce it to correct the exposure
and in low light situations you have to increase light supply. In
automatic mode, your camera will adjust or balance the right amount of
light for you by selecting the right settings with the help of
controllers (Aperture, Shutter, ISO), but in manual exposure mode you
have to set them on your own.
The Controllers of lights
There are three parameters which controlls the amount of light. Together they form Exposure Triangle. And the beauty is they can balance each other.
- Aperture : controls amount of light flow & Depth Of Field
- Shutter speed: controls time of light flow, motion blur & freeze
- ISO: controls light sensitivity & Noise or Grain
Thursday 4 April 2013
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