Sunday, 30 December 2012

Types of light

So, to start things off again, not really a practical post here... more of a thought post.

Have you ever really thought about the different types of light? I don't mean tungsten, daylight etc. Rather, more generally, the broad forms of lighting which can result in a final image?

It's obvious, but I think it still bears thinking about:

1. Ambient light
2. Ambient minus Controllable Ambient
3. Ambient minus Controllable Ambient plus Flash
4. Flash alone (which is really just a version of the one above)

1. Ambient light

In any non-studio situation, I'll always look to make the ambient light do the heavy lifting for the lighting of an image. If you want to light with ambient though, you've got to start thinking in terms of direction and quality of light. Positioning a model next to a window is the classic example of doing this. This step, when done well, is the first step to rising above the everyday photographer who just clicks a photo of what is in front of him or her, without thought about how to improve the quality and direction of the light.

2. Ambient minus Controllable Ambient

The next stage is thinking about how you can control your ambient. This can give you a touch more flexibility than purely the idea of moving into good light. So what can this mean? Example might be to switch off lights and purely use daylight through a window. It might be equally to close a window, and purely use internal lighting. Similarly, using a diffuser in front of a window which is streaming direct sunlight into a building would be another example. I'd also include the use of a reflector in this, where the reflector is reflecting ambient light. This step is the first step to moving on from being a basic ambient light photographer, to being someone who crafts and controls the light around them. This is a fundamental step to great photography.

3. Ambient minus Controllable Ambient plus Flash

This further stage is where it really starts to get interesting. You now have the power to control ambient light almost completely, subject to having sufficiently powerful lighting. Subtlety is the absolute key here though, and it should always be your approach to work through step 1 and step 2 before coming to step 3, although I do have a habit of jumping to step 3 then working backwards when speed is important. I've called step 3 the addition of "Flash" but it's any light source. For most photographers now, that'll mean flash, but for many it can mean constant sources of light such as Tungsten, Halogen, HMI, Fluorescent etc.

The fundamental point to step 3 is the fact that suddenly you're adding new light that wasn't there when you walked onto the location. This can be immensely subtle, such as a small hair light or background light just to bring a subject out, although they're still lit by ambient light in the main.

But sometimes subtlety isn't what you're after, and that's the exciting thing about adding your own light. Suddenly you have the opportunity to build light on top of ambient light, and by doing so, you're controlling the level of ambient. I've found people seem to have trouble with this, so I thought I'd try the approach of this bar graph:

Think of the height of the graph as your overall exposure. If you underexpose, your bars wouldn't reach the top of the graph, and if you overexposed, the bars would go right over the top of the graph. This graph simply assumes there is a correct desired exposure of some form which is indicated when the bars accurately touch the very top of the graph.

So as you can see, if you're only using ambient light such as on the left bar, then it's contributing 100% to your exposure. However, as you add flash power progressively, you can see that the level of contribution from the ambient is decreased. The reality is that you're adding flash power then adjusting the camera to correct for it, which is thereby reducing the ambient light taken in.

You should now see that there is a fantastic opportunity to use a flash light as key and ambient as fill. If you want subtle flash effects, you only slightly overpower the ambient light and it should have a "clean ambient" feel to it, while if you want a contrasty and dark feel, then you significantly overpower the ambient light with flash. Another way to think of it is that you have absolute control of the contrast ratio between your flash and the ambient, right up to the available power of your flash. The more contrasty you want the scene, the more you overpower the ambient, and thereby reduce the fill light coming from ambient.

4. Flash alone

Flash alone is slightly a myth. If you had enough light to focus your camera, then there is likely some form of ambient. Essentially though, this would be studio photography, where you're working in a dark room with ambient heavily overpowered by studio flashes. Why is there a distinct difference here? Well it's a whole different ballgame, because you're suddenly in the position of doing all the work with no ambient to do the heavy lifting. As such, it becomes more about light modifiers, reflectors, diffusers etc.

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