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8/10/2019 10 Things Youshould Know About Flash
1/6
L I b H T I N b H O W T U
I
sin
a
Canon
Spaedlite
540EXhigh
on a tripod
Gary William-
son made
these sun-
flowers pop
against a
dark sunset
W e m aintain that the s ingle m ost important acces-
sory for your
DSLR
is a full-featured T T L flash unit
W ith lightning in a botue, yo u can freeze action
solid, m im ic studio lighting, tam e harsh m idday
sunlight, balance o r unba lance) the color inascene,
an d produce w ild and w eird effects^with n o soft-
warerequired.Here w e presen t a primer on portable
flash th eory a nd practice.
B y D a n
i c h a r d s
^ All flash ph o
are double
exposures.
The two exposures occur
neously one by the am bie
the other
by
th e flash illum
tion.
Youc an vary each of
expo sures for a wide varie
different effects: You can m
them of equal hrightness
uneq ual or widely uneq ua
can give th em different co
8/10/2019 10 Things Youshould Know About Flash
2/6
u can even vary
tter effects, with one exp osure
urred and the other
p. This is what mak es
photograph y so muc h fun
EXPERIMENT
If you're
shooting, say, a foreground
leafy
, don t settle for the auto
ary both the am bient a nd
erent effects.
Adjusting the
aperture affects
both ambient
sthe apertureisthe lens's light
, opening it up or stopping it
lighten or darken both
esprovided the flash out-
tiskept at the same level. (With
eflashset to auto, itwillcompen-
byincreasing or reducing the
m ore on thisbelow. Since
large aperture admits a lot of light,
eflashcan emit less for proper
This will giveyou greater
reach and/or longer battery
Asmall aperture requires more
, and you r reach an d/or battery
USING A W IDE
aperture to
limit de pth of field in an outdoor
force
to exceed your camera's m axim um
debar, page 118 ).
a neutral-density (ND) filter
p (ND 1.8) filter will let you
op to V 2 5 0 sec from
1/8000
sec,
autofocus dicey.
Shutter speed
affects ambient
but no t flash
The flashISa very
ef burst occurring du ring the
tter openinga flash bu rst of
sec will provide the sam e
umination with a shu tter speed
Bounce
flash can
eat up flash
powernot
just because
of the extra
distance the
light must
travel, but
also because
even quite
reflective
walls or
ceilings
absorb
someof
thelight.If
your bounce
shots are
turning
out under-
exposed,
open up the
aperture.
of 1/30 sec as itwillwith a 1/250
sec shu tter
So
you can lighten
or darken the ambient exposure
by increasing or reducing the
shutter speed while maintaining
the same apertureand thu s the
same flash output.
YOU CAN VARY
theshutter
speed and still use autoexposure
ysetting the cam era to aperture-
priority mode. Now, when you darken or
brighten with exposure compensation,
the cam era will vary the shutter speed
but keep the aperture the same.
4
For na tural-
looking nil flash,
underexpose the
flash ex posure.
The idea behind natu ral nil is to
ma ke it look like soft a mb ient
light. As fill flash is o rdina rily
used for back- or sidelit sub-
jects, setting the flash illumina -
tion to the s am e level as the
amb ient l ight makes your strobe
obvious.Tokeep it subtle, use
the flash's exposure compen-
sation to dial down its o utpu t.
Settings in a range of-0.7 to -2
EVusua lly work well.
DON T FEAR
unnatural
fi l l.
For exam ple, a
2 stop
ambient
underexposure combined with full
flash exposure can dram atically isolate
a hum an figure or foreground object.
Flash h as
c o l o r .
While we
think
of flash as white light,
flash, like all visible
light
has a
color
cast.
Accessory flash m anu -
facturers set daylight balance at
around 5200-5500 degrees Kelvin
in color tem pera ture. This is actu-
ally a good deal wa rmer in color
tha n daylight on a blue-sky day
when color temp erature can go
as high as 10,000 degreesK(very
blue), leading to a mism atch in
color balance .Thisis why digital
cameras have se parate presets for
flash and daylight white balance.
Amore common mismatch:
flash with tungsten room light.
With a digital camera se t to flash
white balance, the foreground
subject will appear a neutral color
while background illumination
ou t of the range of the flash will
have a yellow-red cast. (Many
photographers like this look and
8/10/2019 10 Things Youshould Know About Flash
3/6
se t
it
up de liberately) Flip
the
camera s w hite balance
to
tung-
sten,
and
the background light
will shift to neutr al w hile
the
fore-
ground subject ap pears very blue.
Wan t to even the balance? Putan
amb er filter over the flash lens,
and set the cam era to tungstenor
auto white balance.
W I TH H L M you may
need toad danextra step
to coior balancing . Shoo ting daylight
fi lm under fluorescent l ights,
you
would put agreengel CC30)over
the fiash head tobalanceit withthe
greenish fluorescents. You
d
then
place
a
mag enta fi lter such
as the
Tiffen FL-D) over
the
came ra lens
to
neutralize thenow-overall green cast.
6
Autoflash varies
the duration
of the flash.
Modem accessory flash units
automate exposurebyreading
the bounce backof the flash
through
the
len s (TTL). (Many
uni ts
now
make this reading
via
a
brief preflash.)
The
camera/flash brain adjusts
the flash exposurebymaking
the burst shorterorlongerfor
lessorm ore light, respectively
The rangeoff lash bu rstsis
pretty astound ing a t5rpi-
cal accessory unitmayhave
durations from 1/1000 sec to
1/50,000
sec oreven less.
You also adjust manua l flash
power by changing duration,
almost always measured in frac-
tions:fullpower, 1/2,1/4,1/8,
etc., o ften down
to
1/64 power
for the shortest flash duration.
^ USE VERY BRIEFflash
^ ^ dura ti onsforextreme m otion-
stopping photos. Positioning the
f lash close toyour subject, usinga
wide aperture,and settingahigh
iSO w illall shortentheduration
of autoflash,andyoucandialin
high speed m anually, too. Keep
WithAA
batteries,
there is
no
free lunch:
Thebatteries
that give
youie
shortest
recycling
times,
NiMH
rechargeables,
giveyou the
fewest shots
per charge;
the ones
tha t give
youie
most shots,
disposable
lithiums,
havethe
longest
recycling
times.Alkaline
AAsland
in between.
the ambient l ight and/or ambie
exposure iow, though ,oryou m
just capture a ghostthe te rmf
ambient motion biurin afiash
TTL flash wor
better with the
camera in ma
exposure mode.
By
setting the am bient expo
you wa nt m anually, you elim
one variableand canconcen
ontheeffects of various flash
exposu res, positions, etc. Say
you re shootingaseriesofpo
traits outdoors withillflash
wantanambient exposure t
keeps the backgroundat ace
light level,butwiththecam
set to auto,itmight keep adj
this exposure as you change
position, focal leng th,or flas
outp ut. Better to lockitin u s
manual mode.
WITH l UFLASH in a
situation, it soften better
se ttheambient exposure1 sto
a litt le mo re overthemeter rea
This m akes thebacklighting ap
more reaiistic. With portraits,it
heipstoobscure background d
8
Flash follows
same hardnes
softness rules
ambient light
The broaderthelight source
softer the
light.
That s why s
portraits shooters use softbo
umbrellas,andbeauty dishe
their strobes. But the narrow
light source, the hard er the l
Sostudio shooters usesnoo
and gridstoget hard, even h
effects. Placing the light sour
closer to your subject mak es
broaderandtherefore softer
ing the light source farther a
makesitnarrowerandhard
Readallabout the qualities
light in 10ThingsYouMust
AboutLight in
our
May 201
or
at
PopPhoto.com/lighting
CONTINUESONP
8/10/2019 10 Things Youshould Know About Flash
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shutte
burst f
Niko n
Speed
gave C
Walbe
trai l in
I I That Syncing Feeling
Film and digital SLRs use focai-piace shuttersessentially curtains th at ope
and close to mak e an exposure. The curtains m ust be fully open for the flas
exposure, and these events are synchronized eiectronically in the cam era. B
at faster shutter speeds (depending on the ca mera , faster than 1/160 1/2
or 1/250
s e c ,
the curtains never fuily expose the focai plane.
Instead,
the
achieve high-speed exposure by traveling as a s lit across the focal plane.
Fire a flash during this exposure, and you'll have either a thin siice of flas
exposure or no flash im age. Fortunately, most mod em DSLRs have a failsa
that prevents you from setting the wrong sync
speed,
even in m anua i expo
iVIany m anufa cturers '
T T L
flashes offer highsp eed sync, a workaround th
puises the flash rapidly as the narrow slit traverses the focal
plane.
This giv
you flash sync at the fuil range of shutter speeds, at the price of iim ited dista
range. Good uses: fill for fairly close action subjects, or for outdoor portraits
taken at wide-open apertures that might man date very fast shutter speeds.
Rash sync is usuaily triggered at th e start of the shutter cycle. With mo ti
biur pius
flash, though,
this gives the weird effect of the subject mov ing ba
wards. Rear-curtain or trailing sync fires the f ash at the end of th e exposure
ma king for the trailing blur you see in the photo above.
I
NUMEROUS iight-modifying
devices are m ade for shoe-
mountflash,as well as accessories for
adapting shoe-mounters to studio gear
such as stands, umbrellas, and so forth.
Flash falls off
in proportion
to the square of
the d istance.
The beam from a flash unit is
cone-shaped shoot a relatively
close object and most, if not all,
of the light co ne will cover it As
you move farther
away,
though
a smaller portion oft he light
cone hits the subject, as more
the light sprays w ide. At a grea
enough distance, the flash s lig
becomes imperceptible to the
eye as well as to a sensor or fi
And it s a sq uare relationship:
you move tw ice as far away fro
your subject, you get only 1/4 t
illumination on the subject; tri
your distanc e, and you get only
the light. Setting the zoom hea
an accessory flash to tele posit
8/10/2019 10 Things Youshould Know About Flash
5/6
l create a narrow er
cone,
bu t
Y et
jus t becaus e you re far
om your subject doesn t m ean
has tob e . Y o u ca n
and fire from a
P US E FLASH FALLOFF to
* ^ your advan tage by varying
nce t>etween your subject
r subject mov e
For exac t
control over
a multiflash
witch them to
sure,
the major
L fiash system s can operate
and you can vary their out-
ireless controller. But
s pretty easy to adjust multiple
s using the ma nua l frac-
A quick starting p oint for a
fill and back-
e fill for
FOR ELABORATE
FLASH
setups and s tudio
provides
ke readings of m ult i-pop
n mm
to am bient readings,
for balanc ing exposures. O
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