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LET THERE BE LET THERE BE LIGHT LIGHT SOME THOUGHTS ON FLASH SOME THOUGHTS ON FLASH PHOTOGRAPHY PHOTOGRAPHY

LET THERE BE LIGHT SOME THOUGHTS ON FLASH PHOTOGRAPHY

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Page 1: LET THERE BE LIGHT SOME THOUGHTS ON FLASH PHOTOGRAPHY

LET THERE BE LET THERE BE LIGHTLIGHT

SOME THOUGHTS ON SOME THOUGHTS ON FLASH PHOTOGRAPHYFLASH PHOTOGRAPHY

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LIGHTINGLIGHTING In the early days of photography the only In the early days of photography the only

source of light was, of course, the sun, so source of light was, of course, the sun, so most photography depended upon long most photography depended upon long days and good weather. It is said that days and good weather. It is said that RejlanderRejlander used a cat as a primitive used a cat as a primitive exposure meter: placing the cat where the exposure meter: placing the cat where the sitter should be, he judged by looking at sitter should be, he judged by looking at its eyes whether it was worth taking any its eyes whether it was worth taking any photographs or whether his sitter should photographs or whether his sitter should go home and wait for better times!. go home and wait for better times!.

The first artificial light photography dates The first artificial light photography dates back as far as 1839, when L. Ibbetson back as far as 1839, when L. Ibbetson heated Quicklime to create heated Quicklime to create LIMELIGHTLIMELIGHT; ; he made a Daguerreotype in five minutes he made a Daguerreotype in five minutes which, he claimed, would have taken which, he claimed, would have taken twenty-five minutes in normal daylight. twenty-five minutes in normal daylight.

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MagnesiumMagnesium

In the 1850’s it was found that burning a In the 1850’s it was found that burning a

strip of Magnesium ( a metal) in oxygen strip of Magnesium ( a metal) in oxygen produced a brilliant light that was used produced a brilliant light that was used for lighting for photographing caves.for lighting for photographing caves.

Soon this form of lighting was used for Soon this form of lighting was used for

Studio portraitureStudio portraiture but Magnesium was very expensive, but became less so in but Magnesium was very expensive, but became less so in

the1870’sthe1870’s

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Flash photographyFlash photography

This, coupled with the introduction of This, coupled with the introduction of dry platesdry plates in the 80s soon led to the in the 80s soon led to the introduction of magnesium flashlamps. introduction of magnesium flashlamps. They all used the same principle: a They all used the same principle: a small amount of powdered magnesium small amount of powdered magnesium would be blown, using a small rubber would be blown, using a small rubber pump, through a spirit flame, pump, through a spirit flame, producing a bright flash lasting about producing a bright flash lasting about 1/15s. It also produced much smoke 1/15s. It also produced much smoke and ash! and ash!

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Then in the late 1880s it was discovered Then in the late 1880s it was discovered that magnesium powder, if mixed with an that magnesium powder, if mixed with an oxidising agent such as potassium oxidising agent such as potassium chlorate, would ignite very easily. This chlorate, would ignite very easily. This led to the introduction of led to the introduction of flash powderflash powder. It . It would be spread on a metal dish, the flash would be spread on a metal dish, the flash powder would be set off by percussion, powder would be set off by percussion, sparks from a flint wheel, electrical fuse sparks from a flint wheel, electrical fuse or just by applying a taper. However the or just by applying a taper. However the explosive flashpowder could be quite explosive flashpowder could be quite dangerous if misused. The smoke made up dangerous if misused. The smoke made up of Magnesium Oxide was also most of Magnesium Oxide was also most unpleasant and slow to disperseunpleasant and slow to disperse

This was not really superseded until the This was not really superseded until the invention of the flashbulb in the late invention of the flashbulb in the late 1920s. 1920s.

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This is a still from a U tube film made by a Texan guyThis is a still from a U tube film made by a Texan guywho made a replica of an old flash pan, filled it with who made a replica of an old flash pan, filled it with powdered magnesium and potassium chlorate and powdered magnesium and potassium chlorate and

ignited it with a percussion cap ignited it with a percussion cap (out of doors! )(out of doors! )

Certainly early flash photography could be a hazardous business. It is said, for example, that M.Riis, working during this period, twice managed to set the places

he was photographing on fire!

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Knowing how much light was Knowing how much light was needed was, as now, a problemneeded was, as now, a problem By varying the amount of flash-By varying the amount of flash-

powder, the distance covered could powder, the distance covered could also be varied. To give some idea, also be varied. To give some idea, using a panchromatic film of about using a panchromatic film of about 25ASA and open flash technique, at f8, 25ASA and open flash technique, at f8, a measure of 0.1 gms of flash would a measure of 0.1 gms of flash would permit the flash-subject distance to be permit the flash-subject distance to be about 2.5 m, whilst 2.0 gms would about 2.5 m, whilst 2.0 gms would permit an exposure 10m away. permit an exposure 10m away.

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Flash bulbs appeared in the Flash bulbs appeared in the 1920.s1920.s

These consisted of a glass globe filed with These consisted of a glass globe filed with a fine Magnesium, Aluminium or a fine Magnesium, Aluminium or

Zirconium strip, and Oxygen, and fired Zirconium strip, and Oxygen, and fired ( as in exploded!) with electricity. ( as in exploded!) with electricity.

The shutter held open, the flash fired, and The shutter held open, the flash fired, and the shutter closed. Hence the “BULB” the shutter closed. Hence the “BULB”

setting on your camera to-day.setting on your camera to-day.

In the 1930s the electric trigger was fired In the 1930s the electric trigger was fired by the shutter itself….by the shutter itself….Synchronisation Synchronisation

had arrived!!had arrived!!

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This is my old flash gun This is my old flash gun from the 1950,sfrom the 1950,s

The bulbs were wrapped in thick blue plastic for The bulbs were wrapped in thick blue plastic for safety, and to correct the yellow colour caste.safety, and to correct the yellow colour caste.

The bulb had 1/10th sec delay in ignition, and so the camera had a “M” connection which delayed shutter opening by1/10th sec. There was a second instantaneous “X” connection for electronic flash in later cameras.

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Electronic flashElectronic flash

Today's flash units are electronic flashtubes. An electronic flash contains a tube filled with Xenon gas,

where electricity of high voltage, stored in Capacitors and charged with small batteries, is discharged to generate an electrical arc that

emits a short flash of light.

A typical duration of the light impulse is 1/1000 second, but can be much less. The majority of cameras now have an electronic flash unit

built in.

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SynchronisationSynchronisation In In fixed lens camerasfixed lens cameras, the Shutter is , the Shutter is

made up of a spring loaded diaphragm made up of a spring loaded diaphragm in the lens.in the lens.

This is manufactured to open very This is manufactured to open very quickly, remain open for the designated quickly, remain open for the designated exposure time and snap close again.exposure time and snap close again.

Electronic flash is of very short Electronic flash is of very short duration, and is synchronised to flash duration, and is synchronised to flash when the shutter is open.when the shutter is open.

The shutter speed setting is irrelevant The shutter speed setting is irrelevant in normal situations.in normal situations.

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Single lens interchangeable lens reflex cameras are quite different.

•The shutter is immediately in front of the sensor and covers the whole of it.

•They are called FOCAL PLANE SHUTTERS

They, traditionally, consist of two curtains which move across the sensor in about 1/100th sec. One curtain starts to expose the sensor, and the second follows to

cover it. Exposure is determined by the size of the gap between them.

For example if the gap is half the width of the sensor, the exposure will be 1/200 sec and only half the sensor is exposed at any moment, and a flash will only

expose half the scene.

In this example the minimum exposure that which would expose the whole sensor is 100th sec.

Modern camera shutters are more complex with several titanium “curtains” working more quickly, but similar limitations will still apply.

•Don’t panic: your modern up to date camera will automatically grab the correct exposure when you switch on the flash, but you need to know the limitations.

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CalibrationCalibration Manufacturers allocate “guide numbers” to Manufacturers allocate “guide numbers” to

flash guns according to their “strength”.flash guns according to their “strength”. These numbers will specify a film speed,These numbers will specify a film speed, usually 100 iso and whether it is in feet or usually 100 iso and whether it is in feet or

metresmetres We used to have to divide the GN by the We used to have to divide the GN by the

distance to the object to set the aperture, and distance to the object to set the aperture, and we still may need to do so with remote flash we still may need to do so with remote flash units.units.

e.g. an object 5 metres away from a e.g. an object 5 metres away from a GN 20 gun will need F 4 to give adequate GN 20 gun will need F 4 to give adequate

exposure exposure

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Guide NumbersGuide NumbersFlash fall-off.

This illustrates everyone’s experience of the relationship of light intensity and distance

The flash Gun in the Illustration has a Guide number of 22 (ie f11 times 2M). Doubling the distance requires 22 divided by 4, or f5.6. or four time the aperture.

Your camera will calculate this for you if in Auto. Mode.

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Older Flash GunsOlder Flash Guns

Early guns had a printed table on Early guns had a printed table on the back to help set aperture.the back to help set aperture.

Then they were made with a diode Then they were made with a diode sensor to detect the reflected light sensor to detect the reflected light from the object and quench the flash from the object and quench the flash instantly, perhaps after 1/10000 sec.instantly, perhaps after 1/10000 sec.

We now have “through the lens” We now have “through the lens” sensors which do the same thing sensors which do the same thing much more accurately. much more accurately.

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Modern FlashModern Flash

Nowadays we expect to stick the flash gun Nowadays we expect to stick the flash gun on the camera, which we set to AUTO-on the camera, which we set to AUTO-PROGRAM and everything is done for us. PROGRAM and everything is done for us. The shutter is set at the minimum setting, The shutter is set at the minimum setting, the object distance is measured, the the object distance is measured, the aperture is set to let in enough reflected aperture is set to let in enough reflected light from the object and the light is light from the object and the light is quenched appropriately and all is perfect.quenched appropriately and all is perfect.

Or so the handbook says….Or so the handbook says….

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Incorporated Flash GunsIncorporated Flash Guns

Most of our modern cameras have a Most of our modern cameras have a flash unit incorporated.flash unit incorporated.

Problems with this:Problems with this: 1. They are of low power, with a range of about 3 Metres 1. They are of low power, with a range of about 3 Metres

at at 100 iso, and a tendency to provoke “noise” at higher iso 100 iso, and a tendency to provoke “noise” at higher iso

values.values. 2.They are too near the lens axis and shine light into any 2.They are too near the lens axis and shine light into any

Eyes’ retinas, giving “RED EYE”Eyes’ retinas, giving “RED EYE” 3. They cannot be angled, or “bounced”3. They cannot be angled, or “bounced”

Christmas is here……Buy a SPEED LIGHT!!!Christmas is here……Buy a SPEED LIGHT!!!

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Advanced flash Advanced flash techniquestechniques

Aperture preferred Automatic Aperture preferred Automatic settingssettings. You may want to exploit . You may want to exploit depth of field effects, and suddenly depth of field effects, and suddenly you need to understand Guide you need to understand Guide Numbers.Numbers.

You may need to go fully You may need to go fully ManualManual, , and the same applies. and the same applies.

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Bounced FlashBounced Flash

STRAIGHT FLASH.

Harsh light. Background shadows.

Reflections and Uneven brightness.

BOUNCED FLASH off White ceiling

No, or soft shadows and even gentle tonal range.

BEWARE OF COLOURED SURFACES!!

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““SLOW- SYNCH”SLOW- SYNCH”

This is a technique of using a LONG This is a technique of using a LONG exposure at night with flash. This exposure at night with flash. This allows background detail to show allows background detail to show through, rather than inky black.through, rather than inky black.

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Rear Curtain FlashRear Curtain Flash Normally ,with front curtain flash, the gun Normally ,with front curtain flash, the gun

fires immediately the shutter is fully open, fires immediately the shutter is fully open, even though the exposure chosen may be even though the exposure chosen may be much longer.much longer.

With With rear curtain flashrear curtain flash the gun fires just the gun fires just before the rear curtain moves to cover the before the rear curtain moves to cover the sensor. sensor.

If you are using “slow-synch” as well this If you are using “slow-synch” as well this allows a retreating car to keep ahead its allows a retreating car to keep ahead its rear lights rather that drive through them, rear lights rather that drive through them, for example.for example.

You will need a tripodYou will need a tripod..

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Rear curtain flashRear curtain flashWith normal flash (front curtain) the rear lights, in this example, leave an image after the car has been flashed. With rear curtain flash the car is flashed later and appears to precede the light trail. This shot was probably taken with a longish shutter speed to record the car movement and background detail (slow sync).

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Fill flashFill flash This is using balanced flash in full day-light if the This is using balanced flash in full day-light if the

object is back lit or has heavy shadows from object is back lit or has heavy shadows from harsh sunlight.harsh sunlight.

This used to be a bit of a gamble, and I used to This used to be a bit of a gamble, and I used to set the gun at a faster film speed to make it set the gun at a faster film speed to make it under expose and give a natural balance.under expose and give a natural balance.

Look at some press photos and see how they can Look at some press photos and see how they can over-expose fill light and make the subject look over-expose fill light and make the subject look artificially bright, like I used to do.artificially bright, like I used to do.

Now its all done for you with the correct camera Now its all done for you with the correct camera and flash settings. The camera will expose and flash settings. The camera will expose correctly for the background and release enough correctly for the background and release enough flash to lighten the shadowsflash to lighten the shadows

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NO FLASH.

Correctly exposed window

Black foreground

AUTOMATIC BALANCED FILL FLASH

Both the window and the flowers are properly exposed

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Off Camera FlashOff Camera FlashFlash guns can be fired remotely.

I used a extension cable for this to give a more contrasty print with modelling shadows and dimmer background.

Modern cameras can fire multiple remote flash wirelessly and this has been demonstrated at previous meetings.

Shadows can be a little hit and miss, and Portraits need careful placing of the nose shadow and precise fill lighting to look “right”.

Studio flash units have a modelling light incorporated to achieve this, and are moved about to adjust relative brightness using the inverse square law.

Flash Meters are placed near the subject and indicate the correct Aperture to use after a trial flash.

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Have a

Great Chrismas

and

Best Wishes for

2010