long lenses
have the opposite qualities to a short lens.
Now then, exactly the same thing with a tripod because the lens and the camera
mustn't move.
This time
we're going to the other end of the spectrum, and i want you to set your longest focal length,
that's your most powerful zoom.
In this case
two and ten millimeters.
Everything else stays pretty much the same, all we're gonna do is to go back to your widest aperture
okay, your lowest F number, that's the shallowest depth of field.
Again on manual focus,
you need to focus in close, now
because of the characteristics of a long lens which has a very narrow field of
view you probably won't be able to do what we did with the wide one, as in
choose the closest focus distance and move in.
So what i want to do is to absolutely duplicate
the size of the tape in the frame
okay, this tapes a bit of fiddling and a bit of thinking.
look at the shot you took with the wide lens and just think how much space
is my piece of red tape
occupying in the picture,
and then setup as close as you can the same shot.
So to do that
you've got to be further away from the tape because of the magnification of
the long lens.
So i'm coming back here somewhere and again looking straight down the side of
the shed,
zoom in
onto the tape
fiddle with the focus now we're just gonna have to tweak the focus
yeah that's about the right place, because i want the tape
same size like in the earlier picture with the wide lens, there we go.
Just make sure that's bang sharp on the tape, there we go, lock your tripod
so that nothing's moving
and move a bit closer to the wall
because i still want to be able to see the trees in the background, it's a tricky shot to
set up this one.
Right here we go.
We're looking straight down the wall
we've got the tape nice and sharp, and
straight away you can see how tiny that block of focus is on the wall,
it's Minuit it's only going about that far either side
of the piece of tape, it's like that, it's
ridiculously small with wide lens the same shot
is going up here a few feet wasn't it?
Now we do the same thing the same exercise as before,
widest aperture
in my case it's F five point six
we'll have a look through
and
we took the picture, as you can see tiny tiny depth of field.
Next, whoops i didn't mean to take an extra shot then.
Go to your middle aperture again, F eleven it's exactly the same as before all you've done
is alter this focal length
and take the same picture.
It's expanded a bit, not a lot but a bit.
Again all the way now
to the smallest aperture, long lenses often have much more apertures, this one
goes down at F forty-five that's a tiny tiny little pin hole
and
retake the shot.
Depth of field at F forty five has now stretched
off down the shed quite a long way hasn't it, we're almost to the end of the shed.
But the trees in the picture, you can see those trees there,
but they're fuzzy and blurred.
With a long lens you can't get the
foreground
and the background sharp it's not do-able, long lens characteristics mean they have a
very small block of focus but you can shift
that block of focus
backwards and forwards along the subject.
Let's have a look and see what i mean. Now we're focused on the piece of tape, as you
rotate your focus we manually
you can actually watch do it slowly you can actually watch the focus
move along the shed off to the trees and turn it the other way
and all the way back to the piece of tape. That's what i mean by having a chunk of
focus which you can roll backwards and forwards
in an out of your picture to get the depth to find the point where you want to
focus.
One quick question you may be asking,
why is it when i set a very small aperture i can't see that in the view finder?
it's because some of the digital slr cameras
the lens doesn't actually stop down to that little tiny aperture until that very
precise moment you press the shutter, if it did
the view finder would be very dark
and you wouldn't be able to see what you were doing.
The aperture is the main control
as to where as to how much you can get with your given lens,
but there's one last piece
and that is that distance between your camera and your subject.
Let's just go back to the original shot at the beginning of the film
again.
It's not quite the same shot as it was at the beginning because the sun has moved round
now.
The trees behind me are soft, just as they were at the beginning of the film,
this time we're going to make the trees come sharp, we're not going to change
focal length of the lens and we're not going to change the aperture, the only thing we'll
change now is the distance between the camera and myself.
So as i start to move backwards away from the camera and that distance is getting
bigger,
jane follows me with the focus the trees behind me as slowly getting sharper
because the focus
ball if you like, is rolling towards them
so now i'm fairly sharp
and so are the trees, so now I've got smaller in the view finder,
but your trees are sharp and
and i'm sharp.
If i come towards you, we're going to decrease the distance
between me the subject and the camera
and as i get closer
so the trees start to go fussy.
I'm coming where i was, i'm coming in closer
now i'm up here
we've got a very soft background and i'm the subject of the picture.
So the things to get your head around with depth of field
are these three concepts,
the aperture is the main control of depth of field or depth of focus on the
camera, as you use a big aperture you have a shallow depth of field
as you use a small aperture you have
an enormous depth of field.
Short wide lenses have a massive depth of field, wide lenses have a massive depth of field
you'll have real trouble with a blurry background
with a wide-angle lens
and finally the distance between you
and your subject
has an impact on the depth of field and how blurry the background is
you will do closeups, macros
have a Minuit depth of field
great for making you concentrate on that bug or insect.