VIEWS: 84 PAGES: 5 POSTED ON: 3/15/2010
Choosing a Flash Gun
Flash In the good old days flashguns were simple and cheap, but using them properly was difficult. You had to use a complicated chart to work out the distance, aperture and film speed, and then trust to luck to get the exposure right – complicated and time consuming – and there was no looking at an LCD to see if the exposure was OK, you had to wait until you got the prints back from the chemist. Then came flashguns that used a “thyristor”, a small sensor on the front that measured the light bouncing back from the subject and cut the flash at the opportune moment to give perfect exposure - most of the time – providing that you remembered to set the correct aperture on the camera. Certainly easier and still cheap (I bought mine for £19.99 at Eric Fishwicks along with my trusty Zenit-E Camera, the only camera I’ve ever owned that you could knock nails in with !) These days flash technology has gone to a new level. For a start most cameras actually have a small flash built in – very convenient, not especially powerful, but certainly adequate for simple jobs. Dedicated flash units now connect directly to the camera’s metering systems, they set the shutter speed and aperture and they know where you’re focussing, what focal length you are using to control the amount of light directly. Many include zoom functions, linked to the zoom of the lens – very sophisticated – and very expensive, a decent flash these days will set you back £200 or more. The other downside is that flash units are dedicated to a particular makes of camera. With a few notable exceptions from third party manufacturers you can’t use a Canon Flash on a Nikon and vice-versa for example. Choosing a Flash Gun If your camera has a built in flash do you really need an external unit? Well if you just take the odd photograph and only use flash indoors or in poor light with the subject near the camera – probably not, but if you ever want to use flash more creatively then you will need an external flash gun. If you have been using a cheap compact camera you will almost certainly have come up against the evils of on-camera flash. It has been said that this destroys more photographs than any other factor. It can cause washing-out of subjects, horrific red-eye, or the over- exposure of one part of the frame and the under-exposure of the rest. Even on more expensive cameras, the little pop-up units that come as standard there simply because they are cheap to manufacture; not only, therefore, do you get a fundamentally flawed piece of engineering, but you get a fundamentally flawed piece of engineering which has been put together with poor components. Anyway – enough of my whinging – assuming that you decide you need an external flash gun, what factors do you need to consider? – let’s take a look. Factors to Consider Fittings Flash units connect to camera in four main ways. 1. Hotshoe. The flash clips on a bracket on top of the camera. Dedicated flash units exchange information with the camera via proprietary digital contacts - small data pins on the flash hotshoe, and as noted you can’t normally mix and match flash units from different makers. A Canon flash unit won’t work properly on a Nikon camera, for example. Or rather, it may fire at full power but flash metering and other features won’t function. With this type of set-up you get fully automatic control, but the flash unit itself is still directly above the lens not the best place in many ways, flash can be quite harsh and even thought the flash unit is further away from the lens than with a pop-up flash red eye may be an issue. However, many units have, or can be used with diffusers, can be angled or bounced, power output controlled and automatic red-eye reduction used. 2. PC Sync Cable Many (not all) cameras have a small round PC Sync socket (nothing to do with computers by-the-way. PC comes from Prontor-Compur - a manufacturer of mechanical leaf shutters back in 1900-and-frozen-to- death). For those cameras that so not have a PC socket, a cheap adaptor can be purchased which sits on the hotshoe Such a connection is simple – no data – no dedication just an instruction to fire – so we’re back to the good old days of setting it all up manually (to some extent anyway). This type of connection is sometimes used for studio flash; hence it remains popular on “high-end” cameras” 3. Hot shoe Sync Cord A dedicated cord connects all the contacts on hotshoe with all the contacts on the flash unit allowing you to move the flash from the camera and retain full dedication. Ideal where you want separation of the camera and flash by a small amount and commonly used for “hammerhead” flash units. 4. Wireless Many cameras and flash guns support wireless operation, the more sophisticated do this by Radio communication, others via a light-trigger (and some by a combination of both). This allows you to put the flash where you want it and not be hampered by wires. Most decent flash units have multiple wireless channels that can be selected – useful if you are in a room full of people with the same type of camera/flash, you can set the channel so that their camera does not trigger your flash or vice-versa. You can also get small light sensitive slave units which trigger another flash when a camera-triggered flash fires (about £4 on ebay). Dedication As has already been said if you want fully automatic, dedicated flash control (and who doesn’t – you need to make sure that you purchase a flash unit which is “dedicated to your camera”. If you forego dedication then you can use almost all “simple non-dedicated” flash guns on your camera - but they will only work manually – you will have to set-up and work out what settings to use two notes of caution. One: Some older flash units (and studio flash) used quite high “strobe trigger voltages” to fire the flash which can damage the flash circuits of modern digital cameras. If in any doubt it’s safer NOT to use older flash units – or use them in situations where they are not directly linked to the camera – no problem with using them wirelessly. Two: Most cameras use the "standard hot shoe" as defined by the International Standards Organization (ISO 518:2006 if you want to get technical), so all standard flash guns will fit this hotshoe (manual only, if not dedicated of course). The exception to this rule is Sony/Minolta who in 1998 adopted the proprietary "Maxxum" hot shoe, designed to be more robust as flash units became heavier. As a consequence however “normal” flash guns do not fit Sony/Minolta Cameras (at least not without an adaptor). Power The power of a flashgun is given as a "guide number" (GN for short). So, if you're choosing a flashgun for its power, this is the number you need to look for. The bigger the GN, the more powerful the flash is and the further the distance it will cover. Flashguns nowadays have their own automatic exposure system. This means that when you take a picture at less than the maximum distance, the flashgun itself will reduce its power output automatically for this reduced distance, giving you the correct exposure. Style It’s worth paying a bit more and getting a flash unit that will swivel horizontally, and tilt vertically especially if. Some people prefer to use “Hammerhead units” as they generally provide high power and long battery life with versatility, have a convenient grip. They also move the flash unit ways from the lens reducing red-eye. Battery Life/Recycle Time The last thing you want is the flash not to fire, battery life can vary enormously – obviously high-power flashes will use more power than but battery life is affected by all manner of things such as subject distance etc, even temperature. The recycle time how long it takes the flash to recharge after shooting. If you are going to do a lot of flash work indoors then one with the option to use mains power may be attractive to you. Personally I always use rechargeable batteries, make sure that they are fully charged and carry a spare set. (By the way – if you are using the built in pop- up flash on a camera that can reduce the number of shots you can take very substantially). The best rechargeable batteries I’ve come across are rated at 2900mAh and can be had for about £6 (inc p&p) for a set of 4 on e-bay. Using Flash It is worth remembering that every time you take a picture with flash, you are actually making two exposures at the same time. One is the picture you would have taken if the flash hadn't fired, the other is the exposure created purely by the flash. In the most typical situation of using flash in a dark room, the light from the flash should totally overwhelm the exposure your camera would make without it. Both exposures are defined by the ISO and aperture, but the camera's exposure is also affected by the shutter speed. If this is slow enough for the camera to have exposed the picture without flash, then you will see both images in the final result. Indoor/Night Direct Flash Using direct flash, that is a camera mounted flash pointed directly at the subject, is very convenient but is not without problems. Direct flash will illuminate the objects in the foreground but objects in the background may appear poorly lit or hard to view. Bleached colours, harsh shadows and red eyes can be common and the smaller the light source the harsher the shadow, so pop-up flash users beware – If you just have to use direct flash, if possible, move your subject away from any walls or large objects. This way you illuminate the person or object without the nasty shadows in the background. Flash with red-eye reduction Red-eye in subjects can often be a problem in portraits taken with flash. It's caused by the flash lighting up the blood vessels in the eye which are then reflected back to the lens. This is a particularly common problem when subjects are close to the lens. Most cameras have some kind of built in red-eye reduction system which is usually a single flash shot, a sequence of flashes, or a more prolonged and less distracting light before the main flash is fired. This works by reducing the size of the pupil prior to the picture being taken. Another way to get rid of red eye is to remove it digitally with Photoshop, or avoid it in the first place by getting the subject to look slightly away from the camera. Diffusers One of the simplest ways to make direct flash less harsh is to use a diffuser, there are a range of commercial diffusers available most simply clip over the flash unit and soften the light. You can also make your own from bits of muslin and/or old plastic milk bottles ! Bounce Flash The idea behind bouncing the flash from another surface is to break up the intensity of the light and diffuse it. Direct flash as we mentioned before tends to leave harsh shadows, overpowering light and sometimes causes "red-eye". Watch the exposure though (should not be an issue with a dedicated flash), and for colour casts from reflected surfaces. Off Camera Flash This is really taking bounce flash a stage further, the flash is mounted off camera, perhaps on a tripod, and triggered wirelessly or by cable. With this method you can have the flash at any angle you desire and of course you can keep the flash near the subject as you move the camera away. If you want to get creative you can have multiple flash units – which is when we start getting into the realms of Studio Flash. Daylight Flash While low light scenes are most often the reason for using flash, it can also be used to more creative effect, even in daylight, to freeze the action of a moving object, reduce shadows, or to create a different temperature of light than that provided by the scene itself. You are pretty much able to just set your camera up as normal with the settings you desire and simply set the flash to auto. Try using Av mode or aperture priority for fill in and just shoot as normal. Take a reading from behind your subject, recompose and shoot. The fill-in flash will take care of the main subject and your reading from behind will take care of the background. Slow-sync and Fill-in flash It may seem odd but apart from low light situations, the other key time to consider using flash is in bright light – so called “Fill-in Flash” is weaker than regular flash, but is strong enough to add light to darker areas of the image such strong shadows. This is useful for situations when the subject needs illuminating but the background doesn't, or when daylight alone casts shadows onto a subjects face. It can also be used to add attractive “Catchlights” to the eyes of subjects Slow-sync mode activates the flash when using slow shutter speeds and is useful for balancing the light between background and subject, and so is often used in night time portraits.
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