By Rob Nyffenegger
Editor’s Note: Sadly this is the last in the Foto PhreakZ series. Keep following Rob’s work on his website, Rob Nyffenegger Photography.
Episode 5 – Photographic Triangle
What is the photographic Triangle?
There are three basic settings on which photography is based. These are: ISO, aperture and shutter speed. Each one has an effect on the other. For a given exposure, whatever you change on one side of the triangle, you must balance out on another side. You as the photographer need to determine the most important settings for your purposes.
These three settings allow you as the photographer to take control of how the final image will appear dependent on your desired outcome.
ISO stands for the International Standards Organisation and the setting in regards to photography, describes the sensitivity of your camera sensor. When film was being used, it represented the sensitivity of the particular roll of film.
|ISO settings: 100, 200, 400, 800, 1600, 3200, 6400, 12800 etc|
Higher ISO numbers indicate higher sensitivity and means that the recording medium absorbs / records available light faster, while the smaller ISO numbers indicate less sensitivity, or slower absorption / recording light rates.
Think of the sensor / film as being made up of grains of sand. Smaller “grains of sand” require brighter light / more time to capture an image as opposed to coarser “grains of sand,” that absorb light faster. This property is handy to know when you are photographing in darker situations. The higher ISO settings will allow you to capture an image when it may otherwise not be possible.
There is always a give and take in photography. In this case, the higher ISO settings also introduce “noise,” in digital images – what was grain in film speak. So the higher the setting, the more pronounced the noise in the image. There are levels that can become unacceptable since it reduces the recorded quality of the image. However, depending on the circumstances, the significance of an event can help you in determining what the limit on the ISO setting will be. If it is a once in a lifetime occurrence and you require the highest ISO to capture the moment and you must get the shot, then getting the photo takes precedence over the introduced noise.
Always shoot on the lowest ISO setting you can to get the image you want. This minimizes noise in the final image and results in a better quality photo.
The aperture determines how much light is allowed to pass through the lens onto the recording medium, similar to how the human eye’s iris works. More ambient light means you can reduce the amount of light needed to record an image. One way to achieve this is to close down the lens aperture.
Now the setting values used to describe the aperture are opposite to what you might think they should be. For example, setting your aperture to f2.8 (aperture values are referred to as f-stops and is the ratio of focal length to aperture diameter), indicates a wide open iris and allows a lot of light to pass through to the camera sensor. A setting of f11 indicates a smaller aperture and hence less light getting to the sensor.
Now for the other effect of changing the aperture – altering the depth of field.
Depth of field (DOF), is the distance between the closest and furthest objects that are acceptably in sharp focus in your image. Altering the aperture on your lens also changes the depth of field in your image. To make things a little more exciting, DOF is also affected by lens focal length and the distance between the photographer and the subject. A photographer has to take all of this into account when capturing images to achieve a desired end result.
The above series of images shows the DOF change as the aperture is increased. The settings also demonstrate the adjustments required to maintain the same exposure level when reducing the size of the aperture.
The shutter speed on your camera determines how quickly the camera captures an image. Shutter speed settings look like this:
1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1”, 2”…. BULB*
The speed setting of 1 over a number is how fast as part of a second the shutter fires. So, 1/250 reads as one two hundred and fiftieth of a second and so on. So, 1/8000, is a very fast shutter speed and usually the limit of most DSLR cameras, with specialized cameras able to go significantly higher (1/100 000 for example), for high speed photography.
As the photographer, you need to determine what is the most important thing you are trying to achieve with the shutter? Am I trying to freeze a moment in time or convey motion? Can I use a slow shutter speed to capture more light or is the subject in motion and will this blur and possibly ruin my shot?
Experience will develop your sense of what speeds to shoot at in certain circumstances. For example, trying to take a photo of a helicopter or propeller aircraft showing blur in the blades, requires a shutter speed around 1/160 of a second. Using a faster shutter speed over 1/250 will freeze the rotating blades and the helicopter or aircraft will look like it is hanging in the air and unnatural. The same is true for sports. Are you freezing the moment or trying to show motion?
Compensating Exposure settings – As I mentioned, when you change one setting in the photographic triangle, you need to make an adjustment on one of the other two settings.
- F2.8 @ 1/500 = F5.6 @ 1/160th – keeping ISO the same
- F11 @ 1/15th = F8 @ 1/30 – keeping ISO the same
- F 8 @ 1/250th = F4 @ 1/1000 – keeping ISO the same
- F 4 @ 1/500 = F11 @ 1/60 – keeping ISO the same
- ISO 400 F4 @ 1/250 = ISO 200 F2.8 @ 1/250 – keeping shutter speed the same
Remember Foto PhreakZ – get out there, get Phreaky and get to know the photographic triangle. Build your understanding on how each setting affects the others and how they can be used to capture the best quality image. There is always give and take in the photographic triangle and when you change one setting, you’ll have to compensate using one of the other two.
Thank-you for reading Foto PhreakZ. I hope these episodes have helped in gaining a basic understanding of photography as well as stirring those creative vibes. Happy shooting!