Not the cleaning product; the lighting one. But you knew that.
I’ve written before about my use of flash, but I’ve never written about yours. What made me think about it was an article on Emulsive, plus Em’s own opinions on the unhelpful arses who tend to answer questions on social media.
So here you go: flash 101. That said, this is not about how to light a scene with flash; this is about connecting a flashgun to your camera and getting the exposure about right. You can then learn how to use flash lighting by trying stuff out.
We’re talking here about electronic flash. There may still be the odd bulb or Magicube around, but they must be rarer than free beer.
Electronic flash – let’s just call it flash – is a very brief and intense pulse of light. Packing even the small amount of energy from a battery into a very short pulse means that the flash can be very bright – the candle that burns half as long burns twice as bright, as they didn’t say in Blade Runner.
Your camera has a connection or method for triggering the flash just at the point the shutter is fully open. Most cameras have a ‘shoe’ bracket that the flash clips into, called a hot shoe because it has an electric contact in it to trigger the flash. Older cameras have a variety of fittings. Without the contact (a cold shoe) or without the shoe, you need to find a little round socket that a flash cable can plug into. Some older flashguns will take a cable connection, some even have a cable fitted, or you can find adapters that take a cable feed into a hotshoe fitting. If you need to find the cable port on your camera, it looks like a miniature version of an old coaxial TV socket. It can be set flush in the camera body or be on the side of the lens like a short stub of pipe. If it is labelled or there are several, use the one marked X or PC. If it’s on the lens, there may be a pointer with X, V and M symbols. Set this to X. Some old Russian cameras have a setting around the shutter speed dial for M or X. Again, set it to X. The X setting fires the flash when the shutter is fully open. The other settings are for flashbulbs. If your camera has a hotshoe and none of this other nonsense, it’s already set up to use flash.
In reading order: cold shoe; hot shoe; cable socket on lens; flash setting on lens; cable sockets in body; flash setting on shutter speed dial. The last one also shows an X on the speed dial, which is the fastest capable speed for flash, in this case 1/30.
A word about putting old film-era flashguns onto digital cameras: care. I’ve heard that some old flashguns can send voltage back down to the connection that triggered them. I hear tell that this can damage some modern digital cameras. If you are worried, buy a cheapo Chinese radio trigger to fire the flash with.
So, now what?
Rule 0 – get your hands on at least one flashgun. Ignore the ones that are dedicated to a particular camera. Even ignore the ones that are automatic or have sensors, although they are handy. Old manual flashguns are unloved and cheap. Get some.
Rule 1 – you control the exposure of the flash using the lens aperture. The flash pulse is much shorter than even your fastest shutter speed, so the shutter speed can’t reduce the amount of flash light. In fact you may need a slow shutter speed. Both curtains of a focal plane shutter have to be out of the way, and sometimes this only happens at speeds slower than 1/125 or even 1/60. Check on your shutter speed dial for a speed that’s a different colour or a setting marked X. You should only use this speed or slower.
Rule 2 – the flashgun has a way of telling you what aperture to use. Some flashguns have a distance vs aperture calculator on the back. Or you can try to find the Guide Number (GN) in the manual or online. The GN will be a distance and an ISO, so something like 12 metres (100 ISO) would be typical. If you were shooting at 100 ISO, focus on your subject and read-off the distance. Divide your GN by your subject distance (in the same units) and that’s your aperture. So if my subject was at 3m, with this flashgun I should use 12/3 = f4 as the aperture. At 400 ISO I could close-down by two stops, so f8.
Rule 3 – surfaces. Flashlight bounces and fills like a torch beam. If you are shooting indoors, you might get smoother and rounder light by bouncing the flash off a wall or ceiling rather than pointing it directly at the subject. This is where you really need an automatic or sensor flashgun, as they can sense the right amount of light rather than trying to use the GN.
Be aware that flash bounced off a green wall will light the subject in green.
Rule 4 – slaves. These are little sensors that (usually) clip to the hotshoe fitting of a flashgun. They sense the brief pulse of a flash going off and trigger the flashgun they are attached to. They can do this fast enough that your camera sees both flashes. This is great for any old flashguns you can find (rule 0) – put a slave cell on them, maybe some coloured cellophane over the light and put them round the back or side of your subject. Or in the next room to shine through the door. Or inside a car or house you are shooting from the outside. Now you get to play with your light balance. To start with, unless you are after an effect, make sure the GN and subject/ backdrop distance for your slave flashes needs a wider aperture than your main flash. Then they will throw less light. Some flashguns will let you reduce their output. Or you can tape a tissue over the light. If you don’t want to trigger the slaves with a flash on the camera, fire one of them with a radio trigger or a long cable.
A slave cell also lets you fire separate flashguns from a simple point and shoot. Tape a bit of tissue over the camera flash if you need to tone it down.
Rule 5 – fill-in. It’s possible to balance the light from a flash with the daylight on your subject so that the flash fills-in the shadows. Measure your subject distance, refer to your GN and set the aperture one stop smaller/ darker to underexpose the flash. Then adjust the shutter speed to expose the scene correctly as though the flash was absent. If the shutter speed you need is faster than you can use for flash, you need more flash power or to get closer. Cameras with the shutter in the lens can usually work with flash at any shutter speed, so are good at fill-in lighting.
Get this right and it looks like you have used a reflector to fill the shadows (without needing an extra pair of arms). You could also underexpose the background for drama. Or put a blue filter on the lens and a yellow one on the flash to make the background go day-for-night blue.
Rule 6 – play. Flash freezes motion, so follow a moving subject with the shutter held open on B then trigger a flash just before you lift your finger. Try multiple flashes for a strobe effect. Try a flash from one side through an orange filter and one from the other side through blue, to get that modern orange and teal look. Put a flash on the end of a selfie stick, trigger it with a slave and you have instant side-lighting. Get a chum to point a flashgun at the back of a subject at night and fire it with a radio trigger to get backlighting. Put the camera on a tripod at night, lock the shutter open and walk around your subject firing a flash at it. Have fun.
Want more? Read the Strobist.
See? Nary a snarky comment made. It can be done.