for you to ensure that all your pictures are bitingly sharp
it's important you understand how depth of field works.
Depth of field is also called depth of focus, i
call it depth of field. Imagine your depth of field to be a block if you like of sharpness,
which you can move
front to back
in your picture
Now if you wanted to shoot a landscape you'd probably want lots of depth of field
you want a great big blocker of sharpness going from just in front of your camera to
off to the horizon so that everything is sharp, because it's the whole scene you're
interested in.
With a shot like the one i'm standing in,
you probably want to concentrate your viewer
on the subject
and make the background a bit soft, therefore you need a very
small block of focus, or depth of field, in this case it goes from just in front of me to
just behind me.
okay
Here's an exercise which i strongly recommend you do to get your head around this
block a focus i spoke about which rolls backwards and forwards into the picture.
first of all
set your camera onto aperture priority
don't use full program because you've got to control the aperture for this exercise,
aperture priority means that the camera will sort out the shutter speed and the exposure for you.
Aperture priority,
then put on your shortest lens or set your zoom to its least
magnification, that's its lowest focal length, they're all the same.
what i want is a short lens, in this case i'm using eighteen millimeters.
next put your focus onto manual,
and manually select the closest distance that you can focus manually with your
lens.
some lenses like this one had a distance scale on, some don't, what you have to do is look
at the ground and just focus it so it's closely focused as it will go.
and finally use a tripod
you can't do this exercise if your camera moves, even the tiniest bit it's
critical that the camera stays still throughout.
If you haven't go a tripod go
and steal one. Now over here on the shed
isn't just the right place whether a nice great wall going off down that way
and there's nothing impeding the view off to the trees in the field beyond,
Don't try this on a wall which has got another wall a few yards up there going the other way, you need
a nice open straight
edge to look along.
Now, we've set our focus nice and short and close
with your tripod here getting close to the wall.
You may notice that I've got some red tape which I've actually stuck here,
because that's our reference point, that's where we're going to have the camera
focused.
without changing the focus this is a little tricky one, you've got to focus
by moving the camera backwards and forwards until the tape comes sharp in
the picture.
Because we've got to make sure we're as close to the tape as we can get
and have the shot, and have it sharp.
great I've got all of that lined up.
All we have to do now, is
is take a picture.
You can see the tapes nice and sharp, but
and as we go along the wall of the shed
the sharpness in the shed is going from about here,
up to about here
up here it's all distinguishable, but in the horizon you can still see the
trees but they're a little bit soft.
So the next part of the exercise isn't to change anything but the aperture.
now i want you to set
a middle range actually, i'm going to go with F eleven, okay that's about half way
along your aperture range.
take exactly the same picture
Straight way flicking between the two
you can see that
it's sharper and the F eleven shot and the trees in the distance are sharper
than they were in the wide aperture shot.
depth of field your block if you like
has now gone from about here
a bit further along the shed wall to about here.
there's a little bit of softness in those trees when using right into the
picture but not much
the next step set your smallest aperture we're going all the way
to F twenty two on this lens
you may have an even smaller aperture which you set
just go to the smallest one in the shop and again take the exact same picture.
Zoom in, have a look around
Yeah depth of field is now going
from our tape to
all the way along the side of the shed, we're
getting right up to the end of the shed
and a bit further we're getting to the tree over there on the right in
the garden.
but when you get right in very tight to those trees on your average image they look sharp,
but if you zoom right in
the trees in the very distance is still
fractionally soft.
So here's that next thing that effects that block of depth of field,
your aperture is the primary control
but also where you focus
because as you focus further away that's where you're moving that big block of focus
that way or that way in your picture.
I want those trees in the distance sharp and i want this tape sharp
now there is a rule for this and there is an equation that works it out of
Adam storey tried to explain this to me but
can't be bothered.
All you need to know is how it works,
without moving the camera manually set
your focus
to about two feet in front of the camera
okay, that's about a foot in front of the camera, my piece of tape,
i want to now just double that, i'm focusing about here, about two feet away.
That block of focus that you can move backwards and forwards
not only does it go that way, it comes towards you as well.
So all we've done is shift that whole block
that way a bit
to try and get those trees sharp.
If you don't have the distance get someone to stick their finger on the wall
or put a bit of tape there or something and manually focus on it then whip it off,
just focus the other side of your
bit of tape,
and same shot again.
again using this
and bingo you've got
you've got sharp pieces tight and you've you've got a sharp piece of tape and you've got a very very sharp tree in the very very
very far distance.
wide lenses massive depth of field they're great for landscapes and things like that
but if you want a blurry background, you're incredibly unlikely to
be able to achieve it with a wide lens.
to do that
you need the opposite
a long lens.