Hello I'm Graham
welcome to today's video which is on the
introduction to the series where we're
looking at modern digital
technology in this series I hope to be
covering off the differences between the
technologies involved with sensors so
that's going to be their CCD and CMOS
type but I'll also be looking at the way
fabrication obtain sensor technology has
moved so that we can actually embed the
sensors to give us contrast and face
detection to drive our autofocus systems
in our modern cameras however in today's
video I want to start by looking at
answering a question does size matter
does actually cramming any more pixels
on to any given sensor size improve the
image quality let's begin by looking at
just how many pixels we need to display
our image in a modern digital world for
example you might want to display your
image on something like this a Kindle
Fire HD which has a HD display 1260 by
768 or something like 133 dpi we also
might want to look at the monitor we
display and again in our modern
technology system we have 2k screens
which are 1920 by 1080 again our laptops
and our PC monitors all emulate HD
resolution 16:9 format we give the 1260
by 768 on 1920 by 1080 alternatively we
may want to make prints and a recent
survey conducted on my photo blog site
suggested that we only now print at 6 by
4 very few people actually produce
prints anymore in fact the ones that do
relate homes limit them to 6 by 4 very
few people now produced anything larger
than 10 by 8 prints if you look at the
number of pixels required to either give
us a 2k display or a six by four print
you'll find it's nowhere near something
like the 18 megapixels that we see in
modern compact digital cameras in fact
in reality for a HD display of 2k size
we only need 2 K pixels so that's 2
megapixels we only need 1920 by 1080 so
even if I display the image from a 22
megapixel camera to the HD screen over
HDMI the camera will be
winning pixels because it only needs to
send 2k pixels to the display device and
it's the same when we print print modern
inkjet printers normally requires in the
light 300 dots per inch to produce a
very high-quality print a lot of course
will depend on the viewing distance of
either the print or your television the
recommended viewing distance for either
device is going to be one point five
times the diagonal so in this case a six
by four print has a diagonal of 7.25
inches so multiply that by one point
five and the actual theoretical viewing
distance is going to be about eleven
inches so if I view this print from 11
inches I'll see exactly what is meant to
be seen on a six by four inch print the
highest resolution and you get a
beautiful image the same fundamental
rule applies to when you're watching a
large format TV so for example if you
have a 50 inch LED TV the diagonal of
that x 1.5 when you look in a letter
1080p image you can miss it in something
like 6 feet away from it just over 2
meters if you look at a low resolution
image on that screen if you're looking
at a 720p image then you'll notice
pixelation at that distance and you have
to move through either way and the
recommended viewing distance on that
size of screen for a 720p image is
actually 10 feet or 3 meters if you were
looking at a VGA resolution on that size
of screen you'd have to set further back
still to get away from pixelation it's
the same with prints you can actually
print say a 16 by 20 print width nothing
like 300 dpi if you printed it something
like 90 dpi and look at it from the
correct viewing distance of about 40
inches that print will appear a sharp
possessives course printed on a 6 by 4
and viewed at 11 inches and it's the
same with something like these big
appetizing Holdings they appear to be
remarkably sharp you can actually see
hairs on model shoulders and things like
that but if you walk up to those
displace and look at them closely you'll
find they're made up of very large dots
something like 20 or 30 dpi nothing like
300 dpi that we need for these smaller
prints so the larger the print of
larger the display the law the
resolution it needs to be if we're
sitting at a further distance to
appreciate a good quality image so why
do we need 18 megapixels if we're only
going to produce a 2k display or 6 by 4
inch print to answer that question let
me show you a setup for images that I
produced with a digital camera ranging
from 12 megapixels down to 2 megapixels
and as we step through these images you
will not notice any difference in image
quality from the highest resolution of
12 to the lowest resolution of 2
megapixel that's the way that the
screens work we can actually use low
resolution images to display on a higher
resolution screen so even though you've
got a 50-inch plasma TV
Sony a 2k resolution screen so we only
need 1920 by 1080 pixels to fill that
screen any more than that and the actual
processor within the television is
actually pixel binnen it's throwing away
some information it doesn't need it so
even though you start off with an 18
megapixel image when your TV displays it
you're actually looking up just 2 K
pixels do we need all those 18
megapixels to create an image for
display on a HD device or a television
screen or even do we need it for
printing cut six by four well the answer
is in two parts one is that we may want
to crop into that image to improve our
composition or may want to simulate
something like a telephoto crop again if
you crop into the image it's simulating
you zooming in with your camera when you
took the first shot the answer to the
first question is improve the
composition before you take the shot
walk up to your subject I'll move
further about get it framed exactly how
you want it and then take the picture
don't rely on post process cropping to
get the composition you want or don't
rely on zooming to get the composition
you want change the lens to a prime lens
move up to where you want to take the
picture you've got the best possible
image quality of get on that camera and
sensor combination so in theory if we
only wanted a 2k display we only need a
2k resolution camera
and in fact the first digital camera
that I was involved was a 1 megapixel
camera the code I produced back in the
early 1990s and that was capable of
producing three and a half inch by five
inch prints without sexual viewing
parameters in fact the first of the
professional Canon digital cameras again
add something like a six megapixel image
so why do we now need 18 megapixel and
the answer to that of course is
marketing marketing can only drive
camera sales through something it can
define to its customers and they can
define pixels as a way to improving
image resolution an image resolution
doesn't exactly just mean how sharp that
print is or our clear it is there's a
lot of factors that go into actually the
print our image resolution as we'll
discuss in the next video so in truth we
don't need anything like the 18
megapixels that would be enforced to
look at these days in compact digital
cameras I started by asking the question
does size matter or size does matter if
you want to consider dynamic range
you'll get more dynamic range if you add
a larger photo site that's the area of
the set of the sensor which gathers the
light a larger site can actually give
you more of a dynamic range it can
collect more of the photons that are
light waves generate smaller sensors
need more amplification which give you
more noise and that destroys the image
quality if our target device was a
printer then of course we would need
more pixels on the original sensor to
drive the 300 dpi needs of our inkjet
printers so as we move on towards the
higher end cameras now we're talking
between 20 and 25 megapixels again it's
a marketing ploy to try and get you to
buy camera based on specification rather
than needs through performance I'm
hopefully going to show that in the next
video I've shot the same scene with a
range of digital cameras ranging from
two megapixel all the way up to 25
megapixel and you'll be astounded at the
quality that's coming out from those
lower pixel cameras
compared to the higher ones that's it
for this video thanks very much for
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thanks again for watching take care and
bye for now
you