Flash – Let there be light!
We all know that in situations in which there
isn’t enough light, or that the natural light doesn’t work in our advantage, we
use flash, that little bulb that sheds some light on the subject. But what is
that mysterious flash, and how can we use it to our best advantage? In this
tutorial I’ll discuss the flash and its qualities. I will concentrate on
external flash for those of you who are more advanced and I am sure that many
will want to further their knowledge after learning more about flash. A small
warning, I incorporate some advanced terms and concepts and I’ll try to explain
things as simply as possible.
This tutorial’s bright spots:
does the modern flash works?
light with your flash
flash - advantages and options
– not what you think
– Mellowing the atmosphere
for flash photography
of flash photography
1. Introduction to flash photography – Question - how
a photograph is created? That’s right, by light emitting from an external
source reflected off different objects. But what happens when we don’t have
enough light where we are, for example at night or in a dark place? Right
again, we use flash or a long exposure. The second option is in most cases
irrelevant and this is why I’ll focus on the former. The flash’s role is to
serve as a comfortable and available light source and to light the scenes the
photographer wishes to capture.
2. The first flashes – Photography as we
know it began in the 19th century, and right from the start early
photographers thought about solutions to the problems brought up in the first
clause. The first flashes were made of magnesium powders and other materials
that when ignited created a short burst of light. Naturally, blowing up noisy
smoky compounds for a photo was quite unpleasant. How did it work? The ancient
photographer would open the lid off the lens (ancient shutter), held the
magnesium ribbon in his hand, lit it and immediately cover the lens and run
away before the people in the photo begin to complain about the smoke.
3. The modern flash – Thankfully,
flashes today work much more efficiently and comfortably than 150 years ago. We
shall now discuss the flash’s structure and how it operates:
– The flash needs an energy source and in most cases it is 1.5 Volts batteries
that we like to call “AA batteries”.
– In fact there are 2 capacitors, a main one and a secondary one, whose job is
to store large amounts of electricity from the batteries. The power from the
batteries is augmented from 1.5 Volts to about 300 Volts in the capacitors,
while the capacitors charge you can hear a high-pitched sound that anticipates
the flash’s fire.
– This device augments the power from 300 Volts to thousands of Volts (!) and
delivers the power to the flash’s light bulb.
bulb – A glass cylinder filled with Xenon gas, which usually doesn’t conduct electricity.
In the flash process, electricity is conducted from the secondary capacitor
with voltage of thousands of Volts in order to ionize the Xenon gas and turn it
into a conductor for free electrons. After that the main current is delivered
from the main capacitor to the bulb, and is converted to photons, meaning –
light! Naturally, This whole process happens in a flash (…). After the flash is
drained, the process repeats itself.
4. Light measuring with the flash – When the camera
measures light, it takes into consideration the light reflected off the
subject. But how is it that the camera can measure light when the only light
available is about to come from the flash? Good question… The answer is that
the camera shoots a tiny flash right before the real flash and uses it to
measure the light reflected off the subject. The real flash is determined
according to this measurement. For a more detailed explanation, read about the differences
between TLL and E-TLL in section 9.
5. Guide number and Working distance – Every flash has a
guide number (GN), which measures the intensity of the flash, the number is
stated in meters according to ISO 100. In order to double the GN you’ll need to
increase the energy 4 fold.
Formula: To determine the relevant working
distance (the distance the subject shoul be from the camera) with the flash the
following equation is used: GN/F-number (Guide number divided by the aperture).
For example GN 42 in F4 will permit a working distance of 42/4 or 10.5 meters.
What affects exposure with a flash? I see that you’re asking all the right
questions. The relevant factors are:
– The shutter speed doesn’t influence the subject’s exposure when flash is used
because the flash is faster than the fastest shutter speed. This is why the
shutter speed only affects the background’s exposure and ambient light.
b. Aperture – The aperture is
the main factor that affects the exposure with flash photography since it
determines that amount of light that enters the lens. As a rule, use the widest
aperture you can (the lowest F number) in order to use the flash most efficiently.
If we close the aperture then either the flash won’t be strong enough (see
formula in section 5) or it will be too strong and blind the subjects.
– The higher the sensor’s sensitivity is, so the efficiency of the flash will
increase. Doubling the ISO will increase the GN by 1.4 and after ISO 100 will
double the GN.
– That’s an obvious one. The distance between the camera and the subject is one
of the most influential factors on exposure in flash photography – you need to
keep your subject within the flash’s range and is the case of several subjects
it’s recommended to keep them in the same plane from the flash in order to
guarantee equal lighting.
In most advanced cameras there is an option of positive or negative flash
compensation. This function gives us more control on the scene’s exposure by
over or under exposing the subject.
– In reflex (SLR) cameras, when using high speeds, the shutter exposes
the film in several stages and not just once. This is why the synchronizing
speed of the flash is limited to the maximal single exposure speed of the
film/sensor. In most cameras this stands on 1/250 when the usual range is 1/125
–1/500. In some of the digital cameras this problem was solved by using an
electronic and not a mechanic shutter. See “Fast Synchronization” regarding
synchronizing speeds higher than the camera’s maximal sync speeds.
Flash photography modes:
flash – Automatic flash is the simplest mode for junior photographers. In this
mode the camera decides when and when not to activate the flash. I recommend
you use your judgment and not to use this mode.
eyes – With on-camera flash we suffer by the phenomenon of “red eyes” which is
caused by a reflection of the flash light which is close to the lens off the
back part of the subject’s eyes (the retina) which is rich in blood vessels. In
some animals, by the way, the eyes shine and reflect some of this light as part
of a night vision mechanism they possess. Anti-red eye flash fires a
preliminary flash that causes the pupils to contract so that when the main
flash is fired the retinal reflection in minimal. Red eye effect does not exist
with external flash (see section 9).
synchronization – is used in night photography when you want to activate the
flash and maintain the low shutter speed in order to expose the background. The
regular synchronizing speed is usually at a minimum of 1/60 and longer
exposures permit enough light from the background to enter the lens. I
recommend you use a tripod for this mode.
curtain – Unlike front curtain where the flash is fired at the beginning of the
exposure, in Rear curtain the flash is fired at the end of the exposure.
flash – It is used in situations where the daylight is strong but you want to
“fill in” the shadows created by sunlight. For this mode we use negative
compensation flash to soften its effect but still leave enough of it to light
the shadowy parts.
– almost every camera has in internal flash. We will now discuss the
differences and possibilities of the external flash.
a. Power – An internal flash
is weaker compared to an external flash. This is because there is less room for
the flash apparatus we learned about earlier, such as the capacitors, bulb,
transformers and of course the batteries used are those of the camera and so an
external flash will be significantly stronger compared to the camera’s internal
– An external flash solves the problem of red eyes because the distance between
it and the lens is great enough so that the angle won’t allow light to be
reflected off the retina.
to the camera
– There are several ways to attach a flash to a camera, a common one being the
“Hot Shoe”. This is a metal groove with several contacts on its bottom on which
you slide the external flash on. Another way to attach a flash is using a
synchronizing cable and a special flash adaptor.
the Lens (TTL)
– spares us the need to manually adjust the flash before every photo. There are
several variations on the method such as A-TTL, I-TTL, E-TTL etc. The
differences between the methods are the light measuring technique. What are the
differences and how do they work? A flash working on TTL fires without a
preliminary flash and measures the correct exposure while the flash is shooting
and stops the flash when it has been achieved. E-TTL is a more recent method that
has been developed by Canon and is carried out by shooting a weak preliminary
flash through which the camera measures the light with a light sensor and after
calibrating all the chosen data fires the main flash. This method exists in the
advanced Canon cameras developed since 1996.
– Advanced flashes are equipped with zoom heads that adjust according to the
lens’ focal length. In a wide lens the light is dispersed in the space and in a
narrow lens it is focused on a narrow area in a more efficient way to enable it
to reach a longer distance.
– As stated in section 8, the synchronization speed of the camera is limited.
But sometimes the need arises for faster shutter speeds, such as in strong
daylight. This is why “fast synchronization” was developed. The flash emits a
series of ultra rapid fires one right after the other throughout the exposure
and by doing that exposes the film (or the sensor) to light in each stage of
the exposure. The disadvantage of this mode is that the intensity of the flash
becomes much weaker because instead of one strong flash there are a lot of
short weak ones. This is also the reason why the shorter the exposure speed is
in fast sync so will the flash intensity be lower (it flashes less times) until
even from a distance of a meter at speeds of 1/4000 it will be difficult to
achieve good exposure. In electronic shutter speeds you can use higher shutter
speeds than in mechanic shutter cameras.
g. Strobe – In this mode the
flash fires several short flashes for about half a second. It is a good mode in
case you want to see how shadows fall in the scene or achieve special effects
such as motion of freezing it. In today’s digital world this is a less
meaningful function because you can shoot a picture and see on the screen
exactly how the shadows fall. Using this mode is mainly out of habit.
– Meaning flash that isn’t on the camera but is activated as a reaction to
another flash. The firing mechanism is a reaction to the light emitted from the
other flash or through a wire/wireless connection in more advanced flashes. The
first kind of flashes fire in a predetermined intensity while the second kind
fires according to the light measured by the camera as the data are transferred
through the wires (or air in the wireless mode).
i. Repeat – Ultra fast flashes
are determined by the flash frequency per second and the length of the flash.
For example, a frequency of 20 flashes per second for half a second will cause
ten flashes. This is used mainly for creative effects in photography, freeze
is recommended to use a flash from the same manufacturer as the camera since
the communication between them is best.
There are two main techniques with flash photography, the first is direct and
the second is bouncing it off walls. It’s important these walls as white,
otherwise the flash reflected will be in the color of the wall.
– The flash is directed straight forward towards the subject. It is
characterized with harsh shadows and a little lighting from above (perfect for
motor vehicle license quality photos)
Bouncing from above
– The flash is aimed to the ceiling (the existence of a ceiling is mandatory
for the success of this technique), and you take the picture. The advanced
flash knows that it is pointing to the ceiling and will compensate for the long
way it has to go with TTL. The end result if lighting from above that is also
called butterfly lighting and it is soft due to the diffusing qualities of the
Bouncing from the side – The flash is pointed to one of the walls, measuring
the flash is done the same as bouncing off the ceiling and the end result is
quality lighting from one side also known as window lighting or Rembrandt
you see, you can achieve a studio light effect with an external flash.
– A flash usually creates very strong contrasts in the lighting with sharp
shadows because of the small size of the light source. A good way to improve
this disadvantage in by the use of a diffuser. The diffuser is made of plastic
and is placed on the external flash. Its Job is to soften the light and create
gentler shadows and soft uniform lighting. It is highly recommended you use it
in direct flash photography. Take into consideration that it's required to increases
the intensity of the flash to get the same illumination with diffuser. In
studio flashes other, more effective diffusing methods can be used such as
umbrellas, soft box etc. whose job is to diffuse the light even more and to
create very soft and pleasant shadows.
Tips for flash photography – Beyond what we’ve learned there are some other tips
that will probably come in handy:
in the fog/smoke – A lot of photographers that use flash can be found in smoky
environments, such as parties. In these situations the flash is bounced of the
particles of the smoke and the camera is “blinded”. This is why a diffused
flash is recommended in these situations, or even not using a flash at all.
Also, try and not to get too close to the subjects.
from long distances – When using flash in long distance photography you should
try and close the aperture as much as you can, take the diffuser off and point
the flash forward. Increase the ISO a level or two and adjust the conditions so
that the working distance is maximal using the GN formula.
the flash off the camera – You can take the flash off the camera and work with
it by pressing the “shoot” button on the flash. Automatic flashes will shoot
with full intensity but manual flashes are more flexible. In this way you can
achieve interesting exposures.
flashes per scene – Define the camera to the longest exposure possible, take
off the external flash and start flashing a lot, really painting with light.
The shutter should be set to around F5 to prevent light from being smeared and
to prevent flash over exposure.
of Flash photography
– I am adding some examples for different applications of the flash photography
guide for demonstration.
Shooting models on the beach – An example of external flash Nikon SB800
on a tripod while shooting a model (my ex-girlfriend) on the beach in Netanya.
The flash was on full intensity, the camera was set to F/8 and the shutter
speed to 1/500 at ISO 200 when the camera wirelessly controls the flash.
implementation of the photo – Nina was jumping and I was shooting from a low angle
while the flash fired wirelessly like in the previous demonstration and is not
shown in this frame. Aperture F/7.1 Shutter speed of 1/320 ISO 200. The
background is deliberately under-exposed in both photos to make the photo more
powerful and to bring out Nina, which is lit by the flash. Without the flash
she would have appeared as a silhouette. More examples can be views in my
photography – in macro photography we use extremely closed apertures to add
depth of field to a difficult scene (I recommend you read the depth of field
tutorial and the macro photography tutorial). Because the aperture is so closed,
it is almost mandatory we use flash to light the subject. In real macro
photography we are so close to the subject the lens is blocking the flash, so
we have to take the flash off the camera and work with it wirelessly or with a
synchronization cable. The results are breathtaking. The first photo is lit
from the upper-left side and the second from the left.
– The flash is a unique and advanced device that enables us, the photographers,
to shoot in situations where the available light is working against us. We’ve
learned how it all began, how the flash is built and how it works, what an
external flash is and its advanced functions and how to make the most out of
flash. The possibilities are endless. As always, the best way to learn is to put
the theory into practice.
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