Depth of Field Workshop

7/27/2019 Depth of Field Workshop

1/4

(represented by a low f-stop number like

f/2.8 or f/4) to a narrow aperture (with a h

number, such as f/22 and f/32). The choic

of aperture is key to controlling exposure,

wide apertures let in more light and narrow

apertures let in less, and it also has a big

bearing on depth of field, with wide apertureducing it and narrower ones increasing

Distance and focal lengthWhen it comes to selecting an aperture yo

also need to consider your distance from t

subject, as the closer you are the shallowe

the depth of field will be when youre

focusing close-up and using a wide apertu

the depth of field may only measure a few

millimetres. Imagine, for instance, that yo

using a 70mm lens on a 7D to photograph

Depth of field, or DoF for short, is

the distance between the nearest

and farthest objects in a scene

t appear acceptably sharp in a photo.

say acceptably sharp because only

e point will be truly razor-sharp in your

tures, as your lens can only focus at a

gle distance. However, the sharpness

s off gradually both in front of and

hind the point youre focusing on, anddepth of field is a measure of how far

s sharp area extends. Controlling the

pth of field makes a real difference to

w your pictures look. The less depth

eld there is, the easier it is to blur

ckgrounds, which is often desirable

portraits. Increasing the depth of field

helps you to capture more detail in a subject

or scene, and youll generally want as much

depth of field as you can get when shooting

landscapes and macro subjects.

Your camera doesnt have a depth of

field control as such; rather its governed by

a number of factors and camera settings.The distance to the subject (and the distance

between subject and background), the focal

length of the lens and the size of the cameras

sensor all play a part, although its the choice

of aperture thats generally seen as having

the biggest impact.

For those new to photography, the

aperture is the hole in the lens that light

has to pass through to reach the cameras

imaging sensor. Its measured in f-stops,

and can be adjusted from a wide aperture

You generallywant as muchdepth of fields you can get

when shooting

andscapes

epth of field is anndispensable creativeool but whatxactly is it, and how

an you control it?

Whats depth of field all aboutUseLiveViewtohelpyo

judgefocusinganddeptoffieldaccurately


2/4

EPBYSTEP

et the apertureFor maximum sharpness

youll need to use relatively

arrow apertures. Select

perture Priority and set an

perture of around f/16 (higher

stops can lead to soft pictures).

se this technique to get the maximum depth of field possible when shooting landscapes

How to use hyperfocal focusing

ect one metre away. With a wide aperture

2.8, the depth of field may only be 2cm at

close distance. However, if the lens was

cused on a subject 10 metres away, that

e aperture may give a depth of field of

ost 170cm. Consequently, your focusing

ds to be bang-on when you use extremely

e apertures at close distances, otherwise

ortant details may look soft.

efore you set the optimum aperture

position yourself at the perfect distance

to provide the depth of field you want for a

shot, you need to think about the best focal

length to use. The lens doesnt affect the

depth of field per se when it comes to

aperture selection, f/5.6 on a 20mm lens

offers the same depth of field as f/5.6 on a

200mm lens but the magnification offered

by the focal length does play a part. Longer

lenses have a narrower field of view than

wider ones, so they take in less of a scene,

effectively making everything appear bigger

in the frame. This includes the backg

with any blur becoming magnified to

Sensor size has a similar effect on

depth of field. The larger the imaging

inside the camera is, the easier it is t

shallow depth of field effects this is

the reasons many pros reach for full

cameras. The smaller APS-C sensor

find in the majority of EOS bodies rec

smaller area of the image projected

lens, so everything appears larger in

Turn off autofocusSwitch your lens to the

manual focus setting:

you need to set the lens at a

precise distance with hyperfocal

focusing, and the lens would

refocus if left in AF mode.

Find the distanceVisit www.dofmaster.com

(or use its smartphone

app) and input your camera and

lens info. Youll be given a table of

depth of field measurements and

a hyperfocal distance setting.

Set the distanceFocus the lens at the

distance suggested

the aperture being used. I

image appears blurred, us

cameras depth of field pr

button to show the true pi

Wide apertures reduce the depth of

eld and help to separate the focal

oint from the rest of the picture,

whereas narrow apertures bring more

f a scene into apparent sharp focus.

Although apertures are consistent

cross lenses (an aperture of f/8 has

he same effect whether its used on a0mm lens or a 500mm lens), lenses

ont offer the same range of settings.

or instance, expensive fast lenses

ffer very large maximum apertures for

heir focal lengths, such as f/2.8 on a

rofessional 300mm lens, compared to

/5.6 on a cheaper equivalent. As well

s letting more light in (and enabling the

aster shutter speeds that give them

heir name), faster lenses enable you

o capture a shallower depth of field.

How aperture affects depth of field

f/16

Narrow aperture:

f/2.8Wide aperture: f/2

A wide aperture offers a

band of sharpness. Both

up and distant backgrou

details will disappear int

Such a shallow depth of

demands accurate focu

here, the mallard has moits head, so its no longe

Choosing a narrow aper

extends the depth of fiel

this can be more forgivin

it comes to focusing erro

Narrow apertures can re

slower shutter speeds

blurred pictures caused

camera shake, as seen h


3/4

For landscape photography, or any other situation

that requires an extended depth of field to keep

everything sharp from the foreground to the

background, youll want to use narrow apertures.

However, as weve seen this leads to slower

shutter speeds; this is no problem if youreshooting with a tripod, but if youre shooting

handheld sharpness can be lost through camera

shake. The solution here is to increase the ISO to

compensate. First, set the aperture, then set an

SO that brings the shutter speed within the safe

handheld shooting speed of the lens (aim for

1/focal length, so 1/50 sec for a 50mm lens).

Up the ISO toget more DoF

Although wide apertures reduce the

depth of field, the effect depends on

how far the subject is from the lens.

The farther away the subject is, the

greater the depth of field even when

a lens is used at its widest aperture.

Take these two examples: both were

shot at f/2.8, but at different distances

from the subject. The shot of the goose

doesnt work because the background

still looks comparatively sharp, and thebird blends into it. The dandelion image

is more successful: the close focusing

and wide aperture combine to produce

a shallow depth of field that separates

the flower from its surroundings.

Why distancematters

Previewing depth of field

Pressing the depth of field button accurately

previews the DoF at the selected aperture of f/11

1/160 secatf/4; ISO200

A wide aperture of f/4 means the

extreme foreground and backgroun

detail appears out of focus

The bright view provided by the wide-

open aperture of f/2.8 in Live View

s difficult to gauge the depth of fieldwhen looking through the viewfinder, as

he image you see is shown at the lenss

widest aperture setting; the aperture

ouve dialled in isnt actually set until just

efore the exposure is made. Most EOS

D-SLRs have a depth of field preview

utton, which youll find near the lens

mount: holding this down sets the lens tothe selected aperture, so you can gauge

what will be sharp; the downside is that the

narrower the aperture, the darker the

image in the viewfinder. The alternative is

to use Live View mode: if you hold down

the depth of field button the bright image

on the LCD will enable you to judge the

depth of field accurately, even when using

narrow apertures in low-light conditions.

f/2.8: focusing at 20ft

f/2.8:focusingat1ft


4/4

1/50secatf/16;ISO1600

Its better to choose a narrow

aperture, then increase the ISO to

enable a safe handheld shutter speed

Fisheye lenses5hintsandtipsfor

1 Choose your viewFisheyes generally come in

two flavours: full-frame or

circular. The effect depends

on the lens design and the

size of the sensor inside the

camera, so check the specs

to make sure the results will

be what youre expecting.

3 Exposure issuesThe inclusion of such a

wide expanse of scenery

can cause severe contrast

problems if you have a

bright sky and a darker

foreground. You may need

to shoot several bracketed

exposures, and combine the

images in post-processing.

5 Try before yoWant to have some

fun without having t

splash out? The am

Canon EF 8-15mm f

lens is only 52 for

from LensesForHire

also check out their

guide at bit.ly/IKNB

2 Get closeBecause of the incredibly

wide view of a fisheye lens

(up to 180 degrees, corner

to corner), youll need to get

much closer to a subject

than would ordinarily be

the case in order to prevent

it from looking too small inthe picture.

4 Check the edgesIts all too easy for your feet

or your shadow, or a set of

tripod legs, to appear in

the bottom of the picture in

fisheye shots. Make a quick

check of the edges of the

frame before you press the

shutter button.

picture than it does using the same focal

ength on a full-frame camera; its a bitike cropping the shot in Photoshop.

Attach a 50mm lens to an APS-C D-SLR

ike the 700D, for instance, and its

effective view will be the same as that of

an 80mm lens (50mm x 1.6 crop factor

of the smaller sensor). On a full-frame

camera such as the 6D, theres no crop

factor it captures the full view of the

ens. In order to get the same image size

as on the 700D, youd need to be closer

to the subject, and, as weve seen, the

closer you are to a subject the shallower

the depth of field becomes.Of course, cameras with smaller

sensors can be useful if youre looking

to maximise the depth of field in your

shots, and a technique called hyperfocal

focusing will also help you to maximise

front-to-back sharpness in a scene.

This involves manually focusing the

lens at a distance that will capture sharp

detail from half the hyperfocal distance

to infinity see our step-by-step

walkthrough on page 71. Q

Each month we highlight a Canon EOS D-SLR or type of lens

and provide handy advice to help you get more from your gear

In association with...

SpecialistlensesThe problem with using very n

apertures to extend the depth

is that it can reduce sharpnes

a phenomenon called diffract

wider aperture will produce a

image but with less DoF, so yo

to decide which is more impor

or set an aperture somewhere

middle. Not so if you use a tilt-

lens: these pricey chunks of g

enable you to use a wide aper

maximum sharpness, and the

lens to adjust the plane of focu

maximise the depth of field.

I

Depth of Field Workshop

Documents