Hello I'm Graham I do hope everyone's having a great day welcome to today's
video now if you like many of my other readers are still struggling with the
concepts of aperture shutter speed and ISO then hopefully this video is going
to explain those three parameters for you now the exposure of a camera depends
on three parameters one is going to be the opportunity you've selected the
second one is going to be the shutter speed and the third is the ISO now we'll
break those down into their component parts a lens system has basic components
of a stock length and its aperture now there is a ratio between the aperture
and the focal length which gives us what's called an f-stop and it's
probably better explaining this on something like an old film camera where
cameras like this had dials which showed you the shutter speed and aperture rings
which showed you the actual opportunity of selected with our modern digital
camera we don't have those dials they've been substituted for mode dials to give
us the opportunity of selecting different types of film situations but
by March they don't have shutter speed or aperture control rings they're the
film camera was very tactile and gives you immediate feedback and when were
genuine our aperture so for example if I change the aperture ring on this camera
you can hear the click stops with the digital camera if you don't hear
anything like that you just see a scale change on the camera so in many respects
the film camera was much easier to comprehend when you're learning
photography with a lens whether it's a general lens camera such as used on the
micro 4/3 systems or DSLRs or this older film camera the aperture consists of a
number of metal blades which are constructed in a way that gives you a
perfect circle so as you change the aperture you're changing the diameter of
that circle that aperture controls the amount of light which slow to reach the
sensor or the film in the case of this camera so that is the first part of the
equation we can see the amount of light which will be controlled by the
and it has an aperture scale under this particular lens goes arrest 3.5 up to
f-22 now those f-stop numbers are the ratios
between the hole in the diaphragm they're all in the iris and the focal
length of the lens so if you divide the focal length of the lens by the size of
the hole it gives you the f-stop and that's a mathematical relationship which
stays with any lens so whether it's a 28 millimeter lens call it 35 millimeter
lens or 400 millimeter lens that f-stop number is that ratio of the focal length
divided by the diameter of the hole so it means that that f/8 will give you the
same amount of light whether it's a 400 millimeter lens or a 28 millimeter lens
on any camera system now the aperture also determines what's called depth of
field and depth of field is the zone of focus that we can set it accepted Lee
sharp from the closest point to the farthest point and that depth of field
will change not only with the aperture setting but also on the focal length of
the lens so if you wanted the maximum depth of field you'll choose a wide
angle lens something like the 28 millimeter lens and you'll focus towards
infinity and you'll get the maximum depth of field if you wanted a very
shallow depth of field if you wanted to i select possibly subject then you use a
longer focal length and you close your focus closer to so with something like
the bridge camera which has got an inherent large depth of field because of
the sensor size then you will need to use extended type photo settings and get
the subject as close to the cameras you can and keep the subject as far away
from the background you can and that will give you this nice shallow zone of
focus so aperture determines the amount of light which will reach the film or
sensor if you look at my hair analogy of your curtains in the house you want to
let more light into the house you open the curtains and the same with the
aperture you want to let more light into the camera you open the aperture and you
go to a smaller number so you'll go to F 2.8 if you want to reduce the amount of
light nur comes into your room you'll close the curtains
same with the aperture you will close the aperture down you go to a larger
number like f/8 now if you change the amount of light that reaches the film or
sensor to keep the exposure right you need to change the shutter speed which
there is the amount of time that that light is allowed to stay on the sensor
so if you let more light into the camera to keep the exposure the same you need
to reduce the amount of time that that light will fall on the sensor and that's
the purpose of the shutter in the camera now if you look at this particular
camera you see we have a shutter speed dial and the shutter speeds go from 2 s
all the way up to 2000 now 2 s is 2 seconds or the longest exposure time we
can have with this camera is 2 seconds but what about the other numbers the 1
to 5 to 500 500 etc well they are actually fraction of a second and
they're really 1 over 1 to 5 or 1 over to 5 over so they are one 120 2 or a 1
250 the second I guess because there's not much room on the down to engrave all
that the decision was made just to put the fractions part that you download if
you like off big number so mm really is 1 mm of a second now the numbers on the
shutter speed dial follow an internationally agreed increment and
same with the apertures and internationally agreed increment between
each of the numbers on the lens and there are what are called s stops or
evey numbers so one f-stop change would give you double the amount of light or
half if you go to a smaller number and it is same with the shutter speed so if
you go from one shutter speed faster you will half the number and figure out you
want you to speed slower you'll double the number so for example if you're one
500 you go to a 125th you are shortening that exposure by four times you go from
a 125th to a 500 you are shortening that by four times
so just to recap if you're one 500 then you go to a 125th you're extending that
shutter speed by 4 times go to 125th and you go to
five hundredths then you were shortening that shutter speed by four times so
we'll have no two ways of controlling the exposure we've got the aperture
which controls the amount of light reaching the center and we've got the
shutter speed which varies image of time that that light is allowed to stay on
the sensor that brings us to the third component of exposure which is ISO and
higher cell is a way in which we can change the overall camera sensitivity to
the light falling on the center of the film now again it's an internationally
agreed system of iso 100 200 400 is an internationally agreed system and if you
like the iso is a way of change in the amplifier gain of the amplifier between
little photodiode the point the pixel and the unloaded digital converter which
converts the light into electrical energy which the camera can digitize and
use in its digital processing system and it's like an amplifier in an audio
system if you turn up the amplifier of course you'll hear a louder noise but an
association with that if there's any noise in the system that noise is
amplified so even with the lowest amplification we have so ISO 100 we
still see a little bit of noise in our system because that's the electronic
noise generated by the photodiode itself by the amplifier by the analog to
digital converter all these things introduce electronic noise into the
system which is then digitized and comes part of the system the higher your ISO
number the higher this gain is so the more noise you'll see on your image and
that noise tends to soften the image down so in general tones you always want
to keep the ISO as low as you possibly can it's my recommendation you all use
the base on native ISO unless you've got to move away from that because the
lighting situation so with your bridge cameras always select the lowest ISO and
you'll get the best image quality out of that Center if you are forced to use a
higher ISO then limit the is all you use with a bridge camera with a one to
thirty sensor don't ever go on above 400 you'll destroy the image with a Micro
Four Thirds system you can probably go up to 800 and with the crop frame DSLR
you probably go to 1600 and with a
full-frame DSLR you can use ISO 3200 and above but generally with our bridge
cameras stay under 800 ISO and you'll get the best image quality with the
semi-automatic modes the camera will make the choices for you so if you've
set the ISO to the lowest number of iso 100 and you set the effort into f4 the
camera will then evaluate the light and set the right
shutter speed to give you the correct exposure now if you change aperture to a
larger opportunity go from f4 to F 2.8 the camera season the amount of light is
increased it's actually doubled with onto the sensor so it will reduce the
shutter speed by a factor of two so if the shutter speed is a 125th and you've
gone from f4 to F 2.8 you've increase the amount of light so the shutter speed
will go from a 125th to a 250 to compensate for that and make the
exposure the same so in summary our three components of exposure the
exposure triangle if you like is the aperture which controls the amount of
light reaching the sensor or film it also dictates the amount of depth of
field in the subject the second one is the shutter speed which changes the time
that that light is allowed to fall on the film or sensor and it changes the
amount of subject motion blur so if the cameras over longer there's any subject
movement you'll see subject motion blur so to capture things like sports or
wildlife birds in flight you need to use a very short to speed a 500th or even a
thousand four two thousand if you wanted to stop any subject motion remember the
camera optical image stabilizer is only there to stabilize your hand movements
so if you've got our hand shake that will eliminate the handshake but it
won't take away any subject motion blur due to the subject moving in the shot
the third component is the ISO which it changes the camera sensitivity to the
ambient light that's around so again if you have the lowest ISO you've got the
lowest noise possible in system change to a higher ISO to get the amount of
light although exposure you'll suffer from noise
in the image so it allows to compromise be aware that aperture controls the
amount of depth of field shutter speed controls the amount of subject motion
blur and the ISO will affect the amount of noise you've got in the image so
under those three facts you should be able to go there and take some better
pictures have a look at my father havoc blog you'll find lots more information
about aperture shutter speed and ISO and about camera systems in general and in
particular panasonic lumix bridge cameras I'll put a link to that in the
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for watching please take care I'll see you all in the next one
good bye for now