This is a work in progress, but I thought I would share it here, its not a definitive resource, its just a few paragraphs to open your mind to on camera flash. I am no expert, far from it, but wanted to put across how I came to understand flash use. I will update it and refine it as I can.
How often do you not take a shot because the light isn’t right? Or take the shot anyway and end up with a disappointing photograph? We all do at some point or another. Many photographers will just wait for that magic light, but with the addition of a simple on (or off) camera flash gun, you can create that magical light wherever and whenever. Let’s be honest the pop up flash is a last resort, and often hinders as much as it helps. Avoid it unless you have no choice.
What I hope to do here, is give anyone who has no experience with flash an insight into what is achievable. If flash is used right it can produce powerful images, and if used correctly, you can’t always tell flash is involved. I am no expert, but you will be amazed at the leap your images will take just by getting out that speedlite and using it. Go on go get it now!
I own a Canon, but the theory is the same for any camera, Nikon, Sony, Olympus, the list goes on. This certainly isn’t the be all and end all, some of the theory and instructions are dumbed down a little, my science may be a little intentionally vague in places to ease you in, don’t worry it will get you started.
Flashes will sometimes be referred to as Speedlites, strobes, flashguns, the list goes on but the device is the same. Make sure you have a compatible flash for your camera if you intend to use it on the hotshoe, often a Nikon flash will not work on camera with a Canon and vice versa, so choose wisely. Be very wary of older flashes, they often had very high voltages which will fry your delicate DSLR’s circuits. Newer flashes have very small trigger voltages which are safe to use with modern cameras.
Most flashes and cameras will sync around 1/200th to 1/250th of a second shutter speeds and slower (e.g 1/60th). Any faster and you will get black banding across your images, as the photograph will catch the shutter moving across the sensor or film. Some cameras will sync faster some slower, check your manual and never go faster than this. Generally flashes have two modes that are pertinent to this short guide. TTL and manual.
TTL means “through the lens”, it has many names E-TTL, TTL, TTL II, and uses clever calculations to work out what flash settings based on the focal length of your lens, your aperture and to a lesser degree the shutter and ISO. This is your automatic mode, handy when you are on the move and need to be flexible. If you find the shot too dark or too bright you can use flash exposure compensation
Flash exposure compensation.
Setting flash exposure compensation affects the flash output only. Ambient/natural light exposure will not be effected this way only the flash light. i.e. aperture. Check your manual to find out how to do this.
Manual Flash Control
As it sounds, you control the flash entirely on your own, and can allow you to get really creative. Its far easier than it sounds, is best suited to shoots where you aren’t moving around and changing focal lengths too much, but we will talk about this later. Many flashes go from 1/1 power (full) down through ½, ¼, 1/8, 1/16. 1/32 and maybe lower.
Many flashes will zoom, from 24mm upto 105mm (or more), if you think of this as a cone of light, the longer the zoom the narrower the cone. This is to direct the light coverage at your subject. In TTL this will automatically zoom, in manual you will have to set it, depending on the effect you want to have. Not all flashes zoom but the decent ones will.
Rear Curtain Sync
This simple setting is a must, have it on at all times when using on camera flash. All it means is that the flash pops at the end of the shutter opening, not at the start. A flash pop will freeze action, that pop of light will capture your subject sharply.
With that in mind, its better to have it pop at the end than at the start right? Think of your photos as layers of light building up, if the flash pops at the start, any blur or movement will build up over the top of your flashed subject. Pop at the end and although your background may still have some blur or movement, your subject itself will be flashed and captured nice and sharp. Have a look later on a Dragging the shutter, for an exercise to show you the effect this has. The photograph of a bride and groom with sparklers in the background, below, demonstrates the effect of rear curtain.
The first thing to be aware of, is I always shoot with my Canon in manual mode with flash. To some that may sound scary, but it really is not as frightening as it seems, we will try a short experiment soon for those who are very new to flash that will show you just how easy and powerful the combination of flash and manual camera settings are. I also shoot raw, but that’s my preference, mostly for the white balance control it gives, which can be important with flash use. If you use your camera in Aperture Priority be aware that for Canon’s at least (someone can let me know for other brands) your flash will use fill mode, giving just enough light to match the ambient light, not recommended by me at least.
Working that Light
When you shoot in the sunlight, you have a pretty massive light source, and generally gives a soft spread of light. A speedlite in contrast is a tiny light source only a few inches across which gives a very harsh light and thus a hard shadow.
Light straight on from a flash fun will be very flat and unflattering, it will also look unnatural, especially if it’s in conflict with the direction and feel of the natural light. The secret to getting great light from a small source, is to give that small light more coverage. But how? Let’s understand our basic options.
This for me is the most effective method of increasing the apparent light source. Look for walls, ceilings or use reflectors. Simply bounce your light at an angle so that it hits your subject in a pleasing way. This is the best way to avoid flash shadow (lets face it its ugly in a shot), and gives lovely soft coverage. That’s our main goal right? Before you start though, give some thought to the bounce, the angle your flash head is at, the distance to the subject and how you want it to appear. What direction should it be coming from?. Don’t just bounce forwards either, think about bouncing off walls behind you for really good coverage or to the side.
Give this a try, go on do it now, no time like the present. Select TTL mode for ease. Grab someone, or find something to shoot, take a few shots with the flash direct, then try it bouncing off ceiling and walls at various angles. Note the difference in each shot. Move further away or closer, try again, think about the angle of the flash, and the lighting effect it gives. If your shot is too dark try the Flash Compensation and add a little, too bright, dial it down a little until it looks right. Take note which shots have that ugly shadow and which don’t. Hopefully something will click as you try this and you will realise how powerful a tool bouncing really is! Bear in mind if you are moving around or changing from portrait to landscape you will need to adjust the angle on the flash as you work.
TTL Flash bounced.
On a grey day, the clouds act as a natural diffuser, ever noticed how soft the shadows are on these days? How light seems to wrap around everything? Well you can apply the same effect to your strobe. If you have no ceilings or walls, then a diffuser is the next best option. In effect it is often plastic or other substance which spreads the light out as it leaves the camera. These come in all shapes and sizes, varying from small plastic caps that go over your flash, to white umbrellas often used for off camera flash. Some diffusers are more effect than others.
Balancing Flash light and Ambient Light
When you learn photography, you are taught how aperture and shutter speed interact. We are shown that is we widen the aperture (letting in more light), we can shorten the shutter speed to maintain the same exposure.
Longer shutter = Lets in more light
Smaller Aperture = Lets in less light
Shorter Shutter = Lets in less light
Wider Aperture = Lets in more light
This logic is why camera in manual is the best method to use. Once you get the grasp of the techniques it becomes more of something you feel than a scientific method. I am not going to blind you with jargon, and f stops, just try it, and you will get a feel for how it works.
For the purpose of flash though, things are slightly less dependant… If you can imagine, the flash is a tiny pop of bright light lasting a tiny fraction of the shutter speed, hence why shutter is really more a concern for the ambient light but flash is not
Aperture adjustments effect flash and to a lesser degree ambient
Shutter adjustments effect ambient
Ok so Im simplifying a bit there, but the basic concept is all you need to get started.
To demonstrate this take your camera and put the flash on the hotshoe. Select manual mode, set Shutter speed to 250th, ISO 200, Aperture F8 and your flash in manual on 1/8th power. Make sure you have rear curtain sync on.
Take a shot. You can bounce the flash but keep it constant for this exercise. Chances are the shot won’t be right, in all probability you may find the shot too dark. We could just increase the flash power, or we can easily adjust the aperture to increase or decrease the effect of the flash. If we want to darken the flash, we choose a smaller aperture, maybe go to f10? If we want to brighten the effect of the flash, we use a wider aperture, say f5.6. It may sound confusing but try it and you will see just how easy it is to tweak the effect the flash has on the shot with just the aperture.
Ambient Light and Dragging the shutter
So where does shutter come into it? Well that effects the available ambient light, be that street lights, a sunset or any other light. If the background is too dark for your liking, you can slow the shutter down to let more of that ambient light in. Carry on from our exercise above, once you have your flash settings nicely set, try slower shutter. Dial the shutter down one stop, take a shot see how it looks. Dial it down again see how it looks. Do this right down 1/8th of a second (or lower if you feel like it).
You can have great fun with this and create powerful images. All we do to drag the shutter, is slow the shutter speed right down, maybe to 1/30th of a second, maybe even slower. This is what allows you to mix the level of flash and ambient light to get the effect you desire, and not let the flash overpower your image but rather contribute to it. You might need a tripod for really slow shutters, or you will have to settle for a blurred background and only a sharp flash lit subject.. You can also increase the ISO to let more ambient in without slowing the shutter.
If the image ambient is too bright, speed your shutter to the sync speed remember), if you need even less lower your ISO to a lower setting. Beyond that you can try a smaller aperture as a starting point and adjust your flash power to compensate.
So that is the basics, have a play, take your time and you will learn in no time, that often the difference between a good shot and an amazing shot is carefully used flash. Its well within your grasp.
For more information, try strobist.com, who have great info on flash use. That will also lead you into the exciting world of off camera flash, which I won’t go into here, also known as Strobist technique where you can get really creative!
Special thanks to Brett Harkness Photography who ran an excellent winter wedding workshop, at which I took many of my wedding shots above.