Putting It Altogether, Outdoor Flash

Looking first at manual flash – we have 4 controls: – Aperture, ISO Setting, Flash to Subject Distance, Flash Power. The closer you move your manual flash to your subject, the brighter the light reaching the subject would be, and hence it would affect your exposure. Similarly, it should already make sense that if we increase or decrease the power setting on our manual flash, this too would affect your exposure. 40 Now, considering the controls available to adjust exposure between ambient exposure, and manual flash exposure, we can see that there are two common controls – aperture and ISO. This means that the shutter speed becomes the independent control for available light exposure. So when we balance manual flash to ambient light, it makes most sense to start by adjusting the shutter speed, since adjusting the aperture or ISO in an attempt to change the ambient exposure, will also affect the manual flash exposure. This is a crucial concept then for manual flash exposures – within a certain range, shutter speed has no effect on flash exposure. This is shown in the three images below. The manual flash power, flash distance, ISO and aperture were all held constant with just the independent shutter speed being adjusted for each image. You will see the exposure for the subject (which is primarily lit by the flash) stays constant whilst the background lit by ambient light gets brighter as the shutter speed is reduced thus allowing more of this to affect the final exposure. 1/160 @ f13 1/50 @ f13 1/13 @ f13 41 This key will allow us to better mix flash with available light – by controlling the shutter speed. The simple reason why shutter speed doesn’t affect our manual flash exposure, is that flash exposure is a pulse (or pulses) of light, and ambient light is continuous. You just need the entire image on the sensor be lit by the burst of light from your flash and, as we have seen, the FZ200 doesn’t suffer from high speed shutter synchronisation problems. Now let’s turn our attention to TTL Flash. TTL flash is totally different than manual flash whwn it comes to balancing ambient and flashlight. With manual flash you had the 4 controls for flash exposure – Aperture, ISO, Flash to Subject Distance and the Flash Power. With TTL flash however, none of those have an appreciable influence on the flash exposure. Your camera - flash setup will follow our chosen aperture and iso combination and will adjust any change in the distance to the subject, and give you what it deems to be correct exposure, by adjusting the output (power) from your flashgun. This means that we can now use Aperture and ISO and Shutter Speed – all three controls – to control available light, without having an affect on our flash exposure. (up to the limit of the output power from your flash gun) With manual flash, if you decided to change any of your settings (aperture, ISO, distance or power), you would have had to change something else to still keep correct exposure. 

Factors that affect flash exposure compensation

There are a number of controlling factors which would affect how your camera meters TTL flash, and would therefore affect how much flash exposure compensation that you will need to dial in. These are:  The reflectance of your subject  The ratio of subject to background size  how far the subject is from the background  whether the subject is off-centre or centred in the frame  the amount of ambient light 33  Whether the subject is backlit – (strong backlighting always require a lot more flash exposure compensation). This might seem quite daunting at first however experience gained by trial and error will soon help you to better understand where and when to use flash exposure compensation.

Flash exposure compensation

Before continuing on and discussing flash exposure compensation, which is primarily used to control the flash output power, it is worth spending a moment considering the two options for controlling exposure compensation within the camera: 1). Exposure compensation is used with the automatic shooting modes of P, A and S. and 2.) Flash exposure compensation Setting flash exposure compensation affects the flash output only. Ambient exposure is unaffected. This can be set on the external flash unit flashgun itself or used to control the popup flash on the camera. Flash exposure compensation is used to compensate for the flash output when the flash is used in Auto or TTL mode. It obviously can’t be set when the flash is used in manual output. With manual flash, you’d just be dialling the actual power output level up or down. 30 1.) Exposure compensation I know many new photographers have trouble understanding the concept of using exposure compensation when the scene or subject is light in tone, and conversely decreasing exposure compensation when the scene or subject is darker in tone. It does seem counterintuitive. EV adjustment (highlighted yellow) The reason for doing so, is that your camera’s meter is designed to expose for everything as a middle grey tone and will compensate for these light and dark subjects. If you are using one of the semi-automatic modes (P, A or S) the camera will expose for any light toned subject so as to make it look like average or mid grey. 31 As an example someone in a white shirt against standing against a white wall, will appear under-exposed. In this situation you need to increase the exposure compensation to prevent the under exposure. The same logic holds true for darker subjects or scenes. Someone in a dark suit against a dark wall, will have overexposed, or light, skin tones as the camera tries to make the dark subject again a mid grey. 2.) Flash exposure compensation There are two scenarios to consider when we think about how flash exposure compensation works: One is when the flash is merely used as fill in flash and the other when the flash is the principal or main light source. The flash power adjustment menu 32 There are probably many situations which fall somewhere in-between these, however having a good understanding of these two situations, will give a better sense of what flash exposure compensation does. When using fill in flash (TTL or Auto flash), you will most likely dial down your flash exposure compensation to output just a tiny bit of fill light. So in this case, your flash exposure compensation will be dialled down to around -1 to -3 EV. However when your flash is the main source of light, you will probably be setting your flash exposure compensation to around 0EV to +1 EV depending on the lightness/darkness of your subject and scene. 

Using Semi-Automatic Flash Units

When flash units started to become more popular more electronics found their way into them. One of 25 the most useful additions was the use of a photocell to measure the reflected light coming back from the subject and use this to extinguish the flash at that point. Early units did this by quenching the charge by “dumping” it into a resistor however this was inefficient, as the unused voltage had to be wasted. Later versions used in line transistors which effectively disconnected the voltage from the flash tube once enough light had been emitted. This had the tremendous advantage that power was not wasted and the flash unit only had to recharge from the residual voltage back up to the normal working voltage. Thus we had faster recycle times with longer battery life. Some units have sliding mechanisms with various neutral density filters or varying sizes of holes to change the “aperture” value. These flash units became far more controllable and gained popularity. 

Using External Flash Units

The use of external flash units with the camera really opens up the possibilities for much more creative flash photography and I will be covering this in greater detail in another section. Basically though the camera can control an external flash unit which is inserted into the hot shoe of the camera, or connected via a fully ttl compatible extension cable from the flash unit to the hot shoe of 21 the camera. It does this by a communication link through the hot shoe to the flash unit to control things like the position of the zoom head (if the unit has an auto zoom) and the value of the camera aperture setting if the flash gun is not used in the ttl mode. TTL compatible flashgun inserted in the hot shoe TTL flash gun in TTL mode on the hot shoe 22 Alternatively the flash can be triggered using a wireless flash transmitter and receiver system. However this does not provide ttl control so the flash unit has to be operated in a manual mode (or local auto mode of the unit) 

Flash Distance and Shutter Speed Synchronisation

The range of the flash is really determined by the ISO of the camera. If you are using iISO or Auto ISO the range will be from the closest focus of the lens at its current zoom position ( 30cms or 1 foot at wide setting to 13.5m 44 feet at tele position). Unlike DSLR cameras with FP (focal plane) shutter mechanisms the FZ200 which does not have such a shutter mechanism will synchronise flash across its 19 entire shutter speed range of 1 second to 1/4000 second (in slow sync mode) or 1/60 to 1/4000 in all other modes. This makes it useful if you want to use high-speed synchronisation when using external flash units with high ambient lighting conditions. Understanding the Flash Icons on the display To indicate the flash mode, and its charging status, the icon will on the display to give this indication Intelligent flash in the Fully Auto iA mode Intelligent flash in the Fully Auto iA mode – Charging state Intelligent flash in the Fully Auto iA mode with slow sync shutter Normal Flash enabled 20 Flash charging Fully auto flash Fully auto flash with red eye reduction Slo Sync mode with red eye reduction

Flash Modes in PASM operation

When using the pop up flash with this camera unlike some DSLR or compact system cameras that automatically raise the flash head when flash is thought required by the camera the FZ200 does not. In all modes it is essential to remove the lens hood to prevent shadowing on the image. In some situations in the iA modes it will display a message saying “raise the flash head” however there doesn’t appear to be much logic behind this and sometimes it doesn’t show this even in total darkness! If you decide you are going to use flash then you manually raise the flash head by releasing the lock switch on the side of the flash unit. You have four modes of flash operation you can select Fully Auto Fully Auto with Red Eye Reduction Forced Flash Slo Synch Shutter Mode Fully Auto Mode 15 In this mode the camera determines if the flash is required (based upon ambient light) for the exposure, and, if it does so controls the amount of light required by monitoring the light captured by the sensor in a short pre-flash burst of light prior to the main exposure. It then adjusts the main flash pulse duration to control the exposure. Close up flash will have a very short duration compared to subjects further away requiring a longer pulse of light to build the exposure. If the resulting images are dark or light then as mentioned previously the power can be adjusted 

Type of Liight Source

1. Full Flash. We normally refer to full flash when the flash unit is the principal or only light source for the image – it totally controls the exposure. It is usually essential when working at high exposures or trying to capture small and active subjects, such as insects. One negative consequence of using this method of flash lighting is that it usually produces black backgrounds and harsh shadows when used with small apertures. When used in bright sunlight the sun might be considered as a fill in light source to prevent these two conditions spoiling your image. 7 It’s not usually advisable to use the pop up flash of the camera or use a hot shoe mounted flashgun as more often than not the extended lens, or lens hood, may cause shadowing on the lower portion of your image. It also produces very flat and uninteresting lighting. If no other option exists but to use the pop up flash head or hot shoe mounted flash unit then it is better to add some form of diffuser to the flash to increase the size of the apparent light source. A larger light source provides a softer light. A simple hot shoe mounted diffuser is shown in figure 1.

2. Fill In Flash. Fill in flash is when you photograph a subject using daylight or artificial light as the principal light source and then add some degree of flash exposure to it. The flash is there to provide sufficient light to either lower the contrast if the principal light source is providing backlight or add some extra sparkle on a dull day. One important point to remember here is that you are not using the flash to arrest subject motion but just to add supplementary light to brighten shadows and lower contrast in the image. The ratio of light to dark areas “the lighting ratio” is usually kept to about 1 – 1 2/3 f-stops or simply stated the shadows are about 2 – 3 times darker than the principally lit areas. Remember this fill in flash cannot arrest subject motion so any subject motion needs to be controlled somehow (shooting on a still day rather than breezy 10 or using mechanical restraints on flower stems for example) in order to capture sharp images. 

Types of Light Source

Flash is an essential accessory for any type of photography that requires a high level of lighting either
to provide sufficient light to give us the correct exposure, enough light to allow us to use smaller apertures to get increased depth of field or to freeze action in our subject. Having an independent light source allows us to operate in difficult situations and achieve results that would be impossible in natural light. Flash arrests subject movement and permits us to use smaller apertures, and, combining this with low ISO settings for maximum image quality and saturation. Flash also adds tonal contrast to the image and additional sparkle in poor lighting conditions. When it comes to macro photography involving plants and insects it gives us the freedom to operate tripod free allowing us to track our subject or achieve the composition we want. 4 Learning how to use and control flash is absolutely essential if you are to progress using this light source in your photography. Obtaining consistent and predictable exposures, using flash, is one of the most common problems faced by newcomers and can be thing that prevents most users from adopting flash as a primary light source. To become totally proficient using flash as a light source you need to understand how light works and its effect on the subject. Learning the situations where flash will be helpful to your image will definitely improve your photography. Flash has a few minor problems to overcome – harsh shadows and black backgrounds are two areas, which cause quite a lot of concern to new users. Other criticisms levelled at flash in the past have been the manual calculations involved in obtaining the correct exposure and the unpredictability of the results. This hit-or-miss approach has been the major frustration for a lot of photographers. Modern cameras have higher levels of sophistication and have come a long way to take out the calculations needed when using flash. Most digital cameras now support TTL (through the lens) flash metering to some degree or other. 5 TTL flash works by monitoring the light reaching the sensor and the quenching the flash when the exposure is correct. This sounds like an ideal solution to the problem of flash exposure however TTL exposure for flash is just like exposure for conventional images – there are situations where it can be fooled. If your subject is bright, or darker, than a typical mid – tone subject then you will still need to use some form of exposure compensation in order to achieve the correct exposure for that scene. Again an understanding the metering modes of the camera will pay dividends in getting the correct exposure. Centre weighted or spot metering may help depending upon the subject and its size in relation to the background. When using a manual flash unit outdoors the quoted guide number (that’s the number by which aperture and distance when multiplied together give for a quoted ISO {usually 100}) no longer applies as there are usually no reflective surfaces to bounce back the light onto the subject. Consequently the exposure will be underexposed. If you are also going to be using a diffuser to soften the light than this will also reduce the flash power reaching the subject. If your main interest is using flash outdoors, for wedding photography for example, you may find it 6 prudent to purchase a more powerful flash unit to overcome these limitations.
source http://www.grahamhoughton.com/

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