In this course lesson from
IP-101 we'll go over exactly what you need to create an exposure. We'll be covering key terms, techniques and what it means to create a photograph.
First off, let's talk about what an
exposure is. In the photography world, an exposure is the term we use instead of photograph. An exposure is the product of
exposing the film, or light sensitive material, to light for a certain period of time. The image created on the film, or light sensitive material, is a product of three main things.
- ISO
- Shutter Speed
- Aperture
These three elements combined is what gets us an exposure. We can't have an exposure without these three elements because each element yields a different effect on the exposure.
The ISO referes to the sensitivity of the film or sensor in your camera. When you buy a packet of film, there are numbers on the side, usually 200, 400, 800 or in some cases 1600. These numbers refer to the sensitivity of the film. Lower ISO number, the more amount of light you will need to properly expose the film.
A film with a low ISO is very sharp and clear, not grainy or riddled with noise. However, the higher the ISO, or sensitivity, the higher amount of grain or noise is apparent in your photograph. Also, the higher your ISO, the harder it is to get a clear focus on your subject.
For shooting at the beach in the middle of the day, ISO 200 is recommended whereas shooting at night on a busy city street, one might use 800 or 1600 coupled with a flash.
What does this mean for digital photography?
Well, a lot.
On every professional or pro-sumer camera, meaning it's not a point and shoot, you have an ISO button. This will let you change the sensitivity of the sensor in your camera. The sensor is the digital version of film and works the same way in conjunction with ISO.
A lower ISO means you'll need more light but your image will be clear and sharp, whereas a higher ISO needs less light but yields a grainy and often out of focus photograph.
When using a film camera it is VERY IMPORTANT that you set the camera's ISO to match the film's ISO before putting your film in. If you don't, your pictures will either be white or black.
When using a digital camera, switching different ISO's in the field is easy and doesn't require you to replace your "film" (because there is none?). This is an advantage in field photography and allows for experimentation with different ISO's to create that unique, never before seen, image.
Shutter Speed describes the amount of time your film, or light sensitive material, is exposed to light. Given the speed at which light travels, which is extremely fast (186,000 miles/sec) the shutter can't remain open too long before the film becomes over exposed. An over exposed image is usually very bright and often impossible to make out detail because of it's brightness.
Standardization of photography has given us all common shutter speeds to follow, whereas when we increase the size of our aperture by a stop, we can decrease the shutter speed to balance the exposure. But don't worry, we haven't covered what aperture or stops are yet.
Standard shutter speeds on cameras are usually written in fraction form because the amount of time the shutter is open is usually in fractions of a second. (yes, it can be very fast)
Common shutter speeds include:
- 1/1000 s (the "s" meaning second),
- 1/500 s
- 1/250 s
- 1/125 s
- 1/60 s
- 1/30 s
- 1/15 s
- 1/8 s
- 1/4 s
- 1/2 s
- 1 s
"B" stands for Bulb, which is a shutter speed you might find on your camera. This allows for the shutter to remain open for as long as you hold down the shutter button. The shutter button is the button we press to take a photograph.
Many photographers use a technique in "Bulb" called a "Long Exposure" where they might take a photograph of a busy city freeway at night and all the cars just look like streaks of white and red lights moving down a clear and focused highway. (Weekly Wackness usually promotes the use of Bulb in a reckless, nonsensical way)
Other photographs taken with a slower shutter speed include photographs of waterfalls or creeks. This is an effect called "motion blur" where objects in motion are blurry or stretched. This occurs in most shutter speeds under 1/60 s but if you're shooting a shutter speeds of 1/30 s and below, you'll need a tripod or a stable flat surface on which to place your camera. Why? Well, at shutter speeds lower than 1/30 s the motion blur is so intense that the pulse in your hand will cause the frame to move resulting in a blurry or out of focus photograph.
A fast shutter speed will give the effect of "frozen time," where everything is sharp and clear and in focus and you may see things one is unable to see with the naked eye like a droplet of water frozen in the air or a split second funny facial expression made by a usually good-looking friend.
The faster your shutter speed, however, the more light you'll need to hit the film or sensor and vice versa, where the slower your shutter speed, the less light you'll need to hit the film or sensor.
APERTURE
Aperture is a little more complex than the others, but we'll save the more technical advanced talk for later. First, the basics. Aperture describes how far open the iris is in the lens. Iris, you say?
The lens and the camera body are two separate things. The ISO and Shutter Speed are devices controlled inside the camera body. But something must happen before light can hit the camera body, it must pass through the lens. The lens gathers and focuses the right amount of light, and the shutter speed then controls how long that light hits the film, or sensor, and the ISO determines how sensitive the film or sensor is.
The
Iris is the device within the lens that controls the amount of light passing through. It does this by creating a circular opening determined by what are known as
F-Stops.
As depicted above, when the aperture goes from f/1.4 to f/2 the amount of light passing through the opening is cut decreased by half.
The aperture doesn't only affect the brightness of your image, but also how much of that image is in focus. We call this Depth of Field. When the iris is wide open at 1.4, the background areas will appear more blurry than when the aperture is at 5.6 or 8.
This effect is clearly demonstrated by pin-hole cameras. These cameras have a fixed iris opening that is really, really small. The size of a pin hole. The photograph generated by these cameras are very sharp and everything is in focus.
The depth refers to the focus range. If you're at 1.4 you may have only a half inch or an inch of space that is in focus. Whereas with 5.6 or 8 your focus range is great, a few feet.
All these together, ISO, shutter speed and aperture form together to create the exposure. Of course, focus does too. But in some cases, it doesn't. (see Weekly Wackness) Now you're ready to start experimenting! Don't get discouraged by photographs you don't like, through failure we learn and through learning only then can we succeed! Besides, most artists hate their work anyway!
DIY Practice Exercises
ISO: Practice using different ISO's and notice the difference in grain. (view on a computer monitor or the biggest screen you have) Experiment with these grain levels and sensitivities. A grainy photo isn't always a "bad" photo. Try using a black and white setting on your high ISO photos.
Shutter Speed: Practice shooting objects in motion at different shutter speeds. Take some photos of a waterfall or running creek at a very fast shutter speed and a very slow one. See the differences, note them for your own future uses. Freeze time with fast shutter speeds, capture a friend jumping in the air or a dog catching a frizbee.
Aperture: Use your aperture settings to create multiple depths of fields. Shoot a line-up of objects, or place objects at multiple distances in the background for greatest effect. Remember, higher aperture number, less light comes in, more in focus. Lower aperture number, more light comes in, less is in focus.
What do we call the aperture number?
