Outdoor Flash For Nature Photographers E.J. Peiker

Transcription

1 Outdoor Flash For Nature Photographers

2 Introduction E.J. Peiker Co-founder NatureScapes.net 49 years of photographic experience, 16 years professionally: Audubon National Geographic Outdoor Photographer Barron s Dorling Kindersley National Park Service State Parks Arizona US Navy Marriott Hotels Many Others 27 Years in Microprocessor and Chipset Development and Manufacturing for Intel Corp.

3 What We Will Cover Why Outdoor Flash? Equipment for Best results Understanding Flash Hardware Flash Synchronization Flash As Fill Light Flash As Main Light Balanced Ambient/Flash Exposure Auto-flash vs. Manual Flash Key Message Flash Situation Tips

4 Why Outdoor Flash Using Flash to enhance your photographs in outdoor situations can open up many new photographic opportunities and allow you to get excellent results even in less than ideal conditions: Cloudy Days Shade Mixed Light Backlit Situations High Contrast Situations

5 Why Outdoor Flash Outdoor Flash can be used to handle otherwise impossible situations: Bright background but subject in shade Bringing out colors that might not otherwise be seen Reducing contrast so that your sensor/film can record the scene Color correction on subject without impact to background

6 Equipment What the Pros Use: Powerful Flash Unit for maximum flash range Canon 580EX/600EX Nikon SB800/SB900/SB910/SB5000 Sony HVL-F60M Flash Bracket to avoid red/steel eye and to avoid lens hood blocking Wimberley Really Right Stuff Fresnel attachment to narrow the beam and boost flash output as well as speed recycle time Flash Extender FX (Better Beamer) Harbor Designs MagMod Flash Power Pack to dramatically speed cycle time Canon/Nikon Quantum Cables Off Camera cable Power Pack to Flash cable

7 Understanding Flash Hardware Flash Unit Consists primarily of a high discharge flash tube, capacitor to store charge, and control electronics Capacitor is charged by the batteries. The capacitor is then discharged into the flash tube producing a short duration light pulse Duration is typically from ~1/800 at full power to 1/32,000 sec at minimum power Flash power output is adjusted by a change in the flash duration not in brightness Flash head usually has zoom capability to reduce wasted light beyond the lenses angle of view. Coverage is between 17mm and 200mm for higher end flash units.

8 Understanding Flash Hardware Camera In a basic automatic TTL (Through The Lens) flash system, the camera uses electronics that detect the amount of flash output that is reaching the scene via a light accumulator inside the camera that measures reflected light off of the film/sensor plane. When the light level reaches a predetermined level, it cuts off the flash from further discharging its capacitor. (pre 2005 gear) In a modern TTL (ittl, ettl) flash system, the camera also commands a short duration pre-flash to measure the light required to light the scene on the multi segment meter. It uses the meter segment that is located where the active AF sensor is, thereby biasing the flash output to the in-focus subject. Finally, it couples this with distance information from the lens to make a final flash output calculation. In a manual flash system, the camera simply tells the flash to fire at a specific time. The amount of flash power discharged depends on what flash power setting is selected on the flash by the photographer. Power is modulated via flash duration.

9 Understanding Flash Hardware Flash Bracket When the angle of incidence between the flash head and the center axis of the lens is less than 3 degrees, red-eye will occur in most living things that have a retina Red-eye happens when light hits the retina and bounces back into the camera lens. When the angle of the flash is increased, the light bounces back but misses the lens By elevating the flash or getting it off camera, the risk of red-eye is dramatically reduced Big lenses or large lens hoods can block the output of the flash resulting in part of the frame being darkened. A bracket elevates the flash thereby preventing this.

10 Understanding Flash Hardware Fresnel Lens (Flash Extender, Better Beamer, Project-a-flash) When using medium to long telephoto lenses a large amount of light is wasted to illuminate areas outside the frame The Fresnel lens concentrates this light to a much narrower beam that is usually equal to a 300mm lens field of view Flash power concentration into a tighter beam of light results in the approximate doubling of the flash unit s effective range Since the flash is more concentrated, less flash power is required per shot allowing for faster flash recycle time

11 Understanding Flash Hardware Auxiliary Power Pack Typical flash recycle times on fresh AA batteries are in the 3-15 second range after a full discharge depending on the flash unit and the freshness of the batteries With a Flash Power Pack, the AA batteries in the flash head power the flash unit s control circuitry and LCD panel The flash tube capacitor is charged by the auxiliary power pack resulting in flash recharge times of about a second after a full discharge and much less for partial discharges As a result, the AA batteries in the flash unit can last weeks instead of hours

12 Flash Synchronization Most cameras have a maximum flashsync speed of 1/125 1/320 sec most common is 1/250 with some pro oriented models going as high as 1/320 second This is the fastest shutter speed that can be used to prevent the shutter curtain from blanking part of the flash in a normal flash photograph The shutter speed must be at the sync speed or slower to get a full power flash pulse (1/250, 1/125, 1/60, etc ) Three types of Flash Synchronization Front Curtain (First Curtain) Synchronization Rear Curtain (Second Curtain) Synchronization High Speed Synchronization

13 Flash Synchronization Front Curtain (First Curtain) Synchronization This is the default flash mode for most cameras and flash units Sequence of events: Shutter button is depressed Shutter curtain opens Flash fires Selected exposure time completes Shutter curtain closes Advantage shutter fires as closely as possible to the time when the photographer trips the shutter Disadvantage if photographing a moving subject or at slow shutter speeds, this method can lead to a ghost or trail in front of the image

14 Flash Synchronization Rear Curtain (Second Curtain) Sync Usually selectable via a custom function or menu selection Sequence of events: Shutter button is depressed Shutter curtain opens Selected exposure time progresses to near completion Flash fires Shutter curtain closes Advantage for a moving subject, any ghost or trail will be behind the subject which is much more natural looking Disadvantage if a long exposure is required, the flash will fire quite a bit after depression of the shutter button potentially missing the action

15 Flash Synchronization High Speed Sync Most cameras with external flash units allow shutter speeds much faster than the fastest synchronization speed by putting the camera and flash into high speed sync mode Sequence of events: Shutter Button is depressed Flash starts pulsing at a very fast rate Shutter opens Shutter time completes Shutter closes Flash stops pulsing Advantage flash can be used at any shutter speed which allows for fill flash even on bright days or when wide apertures that require fast shutter speeds are used Disadvantage dramatically reduced flash output and range, flash does not freeze action since it is on for the whole duration of the exposure

16 Taking Flash Photographs Every flash photograph is two exposures in a single frame The flash exposure primarily lights the subject and foreground The ambient exposure lights both the subject and the background Flash power falls off geometrically with distance thereby having less to no affect on the background depending on it s distance relative to the subject Flash exposure is determined by the power output of the flash Ambient exposure is determined by the ISO, shutter speed, and aperture

17 Fill Flash Fill Flash is used to supplement the existing ambient light Primary light source is the ambient light Secondary light source is the flash Use Fill Flash to: Brighten shadows (reduce contrast) add a catch light to eyes balance color in the shade Procedure For Fill Flash Set ambient exposure to be the same as you would for a non-flash shot Ambient exposure is determined by your ISO, shutter speed, and aperture (fstop) Set your flash in a reduced output mode: Suggest using -3 as a starting point for Nikon, and -2 for Canon and Sony Brighter subjects often need less and darker subjects might need a bit more flash power

18 Fill Flash In a Fill Flash shot, by definition, the flash exposure is less than the ambient exposure Canon Pro bodies and Nikon DSLRs show both ambient and flash exposure scales simultaneously in the viewfinder: Two separate scales on some Canon bodies, a flash indicator with the numerical deviation from zero on Nikon. Sony can display the info in the detail mode viewfinder display. All other DSLR s toggle between ambient exposure and flash exposure scales in the viewfinder or the flash exposure reading is on the flash itself you can usually toggle between ambient and flash reading by hitting the lightning bolt button on your camera. In a fill flash shot, the flash exposure reading will be lower than the ambient exposure reading (for example ambient at 0, flash at -2)

19 Fill Flash No Flash Harsh Shadows Dead Eye Lacking in Feather Detail on wings Fill Flash Harsh Shadows Minimized Eye detail including pupil and catch-light Much better dark feather detail

20 Flash As Main Light Flash as Main Light is used when there is not enough ambient light on the subject to make an adequate exposure Primary source of light on the subject is the flash unit Secondary source of light is the ambient light Use Flash as main light in these situations: Dark days Night Deep shade Subject in Shade, background in sunlight

21 Flash as Main Light Procedure for Flash As Main Light Put the camera in Manual or Program mode Insure Shutter Speed is at you sync speed or slower Select a flash power level that provides more exposure than the ambient light In a Flash as Main Light shot, the flash exposure is more than the ambient exposure Canon Pro bodies and Nikon DSLRs show both ambient and flash exposure scales simultaneously in the viewfinder. Two separate scales on Canon, a flash indicator with the numerical deviation from zero on Nikon. Sony on the detail display mode in the viewfinder All other DSLR s toggle between ambient exposure and flash exposure scales in the viewfinder or the flash exposure reading is on the flash itself you can usually toggle between ambient and flash reading by hitting the lightning bolt button on your camera. In a Flash as Main Light shot, the flash exposure reading will be higher than the ambient exposure reading (for example ambient meter reading is -2 and flash at -1/3)

22 Flash As Main Light No Flash Required long shutter speed to expose bird resulting in washed out background Exposure: 1/100, f/5.6 Photographs were taken 5 seconds apart Flash As Main Allowed 2-stop underexposure of background to retain blue ocean color while properly exposing the bird Exposure: 1/200, f/8 Allowed stopping down for better Depth of Field Tip of Bill is sharper

23 Balanced Flash/Ambient Exposure Balanced Flash/Ambient Exposure occurs when the flash and ambient light contribution to the photos lighting is approximately equal Flash exposure scale and ambient exposure scale in the camera are equal Can be useful when background is receiving reflected sunlight and light on subject is behind a cloud.

24 Automatic Flash All modern camera/flash systems have a Through The Lens (TTL) Flash metering system: Light accumulation is measured in the camera during exposure until the predetermined amount of light is accumulated. This exposure is set by your flash exposure setting. Newer advanced systems use a short pre-flash to help determine proper flash exposure (could cause the subject to flinch resulting in an undesirable pose) Once the correct amount of light has accumulated, the flash is shut off. Works well in most situations but does usually require flash exposure compensation to prevent an over flashed look For flash as main light shots, try a starting point of -2/3 outdoors (+2/3 for Canon users indoors if the walls are white) Try a starting point of -2 to -3 outdoors for fill flash. Go slightly more negative if photographing a subject with bright white and slightly less negative if photographing a subject that is mostly dark to mid-tones.

25 Manual Flash If the subject to camera distance is fixed, more consistant results can be achieved by putting your flash into manual mode For Flash as Main Light, read the scale on the flash and adjust flash power until the distance scale on the flash matches the subject distance. For Fill Flash, read the scale on the flash and adjust flash power until the distance scale on the flash is half the subject distance. This will usually give a pleasing effect. Adjust up or down to taste. If using a Fresnel flash extender lens, cut all flash powers above in half Example Flash as main light using Fresnel lens with subject at 20 feet, set flash power so that the distance scale on the flash head reads a 10 foot range Example Fill flash using Fresnel lens with subject at 20 feet, set flash power so the distance scale on the flash head reads a 5 foot range

26 Advantages Manual Flash Flash power is not influenced by the brightness of the background Flash output is repeatable and 100% predictable regardless of the subjects position in the frame Flash output is not influenced by tonality or brightness of the subject Disadvantage Restricts you to a very narrow distance range unless you are willing to constantly change flash power settings Can cause you to miss action at a different distance than you have set your flash power up for

27 THE KEY MESSAGE Every flash photograph is two exposures in a single frame 1. The flash exposure lights the subject 2. The ambient exposure lights the background since flash power falls off geometrically with distance You can control each independently! You have control of the subject and the background independently

28 Flash Photo Situations Situation: Subject is front lit in diffused sunlight with no noticeable harsh shadows Solution: No flash is needed

29 Flash Photo Situations Situation: Subject is front lit in sunlight but the sun has gotten a bit high in the sky or from a bright cloudy sky and the subject is casting shadows on itself Solution: Fill flash add light that is between 1 and 2 stops below the ambient light (flash compensation to -1 on a dark subject and -2 on a light subject)

30 Flash Photo Situations Situation: Subject is side lit with one side too dark to fully resolve Solution: This is a situation where you are trying to get contrast under control. Underexpose the ambient slightly (up to 1 stop) and add flash to compensate. This will bring the bright side back up to the correct brightness and substantially increase the exposure on the dark side thereby balancing the light.

31 Flash Photo Situations Situation: Subject is in shade, background is in shade and it s too dark to get adequate shutter speed Solution: Take a flash as main light shot by setting the camera between 1/60 and 1/250 note that slower shutter speeds will brighten the background but if the subject is not still, may suffer from motion blur

32 Flash Photo Situations Situation: Subject is in diffuse light with brighter background Solution: Add fill flash to restore the light balance

33 Flash Photo Situations Situation: Subject is in mixed lighting (dappled light) resulting in parts of the subject being too dark and other parts too bright Solution: Treat this as a Flash as Main Light situation by reducing the ambient exposure significantly so that it has minimal effect on the photo, say 2-3 stops or more below the ambient exposure and then use flash to light the subject

34 Flash Photo Situations Subject in DEEP shade and the background is bathing in bright sunlight Understanding that every flash photograph is two exposures in a single frame The flash exposure lights the subject The ambient exposure lights the background since flash power falls off geometrically with distance Vary the shutter speed and aperture to lighten or darken the background to taste Vary the flash output to lighten or darken the subject

35 Additional Considerations Light is subject to the inverse square law: A subject that is twice as far, will require 4 times the flash output (2 squared = 4) Corollary A subject that is half as far will require ¼ the flash output Example of how this affects your flash photos: Indoor people shots: Faces are too bright and backgrounds are too dark. Cause background receiving significantly less flash than subject Possible fixes» move subject closer to background (could cause harsh shadows)» move camera and flash farther from subject and use longer focal length» bounce the flash to make relative distance from the light source more equal.» Place remote flashes to light the background

36 Additional Considerations Beware of Av mode and flash Canon does not limit how slow the shutter speed can go with flash in Av mode by default If you are not careful, the shutter speed can become very slow resulting in ghosting or a blurred image superimposed on the flash exposure Recommend Manual Mode, Program Mode, or even Tv Mode if light is changeable to prevent this. Learn to adjust the flash compensation from the camera, not on the flash head Possible on all Canon bodies and all Nikon Bodies except those without built-in flash Faster, can keep eye and subject in viewfinder, can make on the fly flash adjustments Note that Nikon in-camera compensation and flash head compensation is additive. On Canon cameras the flash setting overrides the in camera setting unless flash is set to zero.

37 Homework Assignment Homework Assignment: Set up an object in shade with the bright blue sky as background. Adjust flash power and ambient exposure independently to get different effects: Shutter Speed and Aperture control the brightness of the sky Flash Power controls the brightness of the subject

38 Resources Best article I ve seen on how flash works (Canon centric but applies to all advanced TTL systems): E.J. Peiker s ebooks: Ducks of North America The Photographer s Guide West