Up to this point the only controlled lighting I have used has been using studio lighting, the rest of the time I have had to adjust to my surroundings.
David Präckel: Basics Photography Lighting
Control over lighting means the photographer is able to achieve the exact effect they desire. For example, if they wanted to capture a large depth of field they would need to use a small aperture and this reduces the amount of light hitting the sensor, controlling light means the exact settings the photographer wants to capture are achieved (see Photo progression post Week 5 for more).
Präkel begins by introducing the Flashgun. It is light, fits on top of the camera with the ‘hot shoe’, and is able to create bounced or diffused light to suit the photographer’s needs. Some downsides are, “the exposure is only correct for a set distance, which can produce dark backgrounds and overexposed foregrounds” (Präkel, 2007). Some flashguns can be external, connected by a wire or wirelessly, to allow the photographer full control over their shots light.
Präkel goes on to mention ‘guide numbers’ which is a concept I am still trying to understand. He says, “there are three key specifications for any flashgun – guide number (a measure of flash power for a given film speed), recycling time (the speed to recharge between flashes) and coverage (the angle that the flash beam covers).”
“Guide number = aperture x distance
To work out the aperture: measure the distance to the subject (use your lens scale). Divide the guide number by this distance to get the f-stop. Guide number of 45 (GN) Flash to subject distance is 8m (FD) Aperture is unknown (f) f = GN/FD 45/8 = f/5.6
To work out the flash distance: divide the guide number by working aperture to get the flash to subject distance. Guide number of 45 (GN) Flash to subject distance is unknown (FD) Aperture is f/11 (f) FD = GN/f 45/11 = about 4m”
I began by setting my camera to the window light (turns out setting a correct exposure was too low) and then adding my flashgun to my camera.
This turned out to be exposed correctly on my subject but underexposed outside. To fix this I did my settings again, with the light meter indicating the shot was over-exposed. Adding the flashgun again I took a much better photo of my subject with correct exposure throughout.
Präkel then talks about flash synchronisation. This is important when using cameras with a manual shutter as if the shutter speed is too fast, only some of the image will be affected by the flash. The limit on the Nikon D7000 is a 250th of a second.
He also touches on how the flash duration can affect how a photo looks. Instead of having a very quick shutter speed, the light being so fast has the effect of freezing a moving object whilst having a manageable shutter speed.
This comes on to rear curtain photography
This is achieved by having more than one flash with a relatively long exposure, one at the start and one at the end, in a dark environment. Using the example of someone running, with one flash at the start and on at the end, an initial outline of where the subject starts is formed. The second flash is the stronger outline of the two and motion blur is behind them. (This is seen better in this image);
The book goes on to talk about the on-camera flash. This flash is unflattering and can lead to red-eye and, if using a wide angle lens, can lead to hot spots of light. The on-camera flash also only goes in one direction and gives a very flat frontal light. But it is good as a fill light in an already light situation.