Friday, February 21, 2014

The F Stops Here: Photography Basics Part 1

Photography Basics Part 1: A Practical Guide to Aperture

View Part 2
View Part 3

This is going to be the first post in a small series explaining some technical photography basics which can help you improve your photography skills. With the improving sophistication of automatic metering systems in digital cameras, technical knowledge of photography is becoming less necessary. However, if you want to have artistic control over your images, you should learn a few basics.

What is an F stop?
"F stop" is another term for "aperture." Aperture is the name for the hole through which light reaches the film - or digital chip - when the shutter is lifted. This allows for exposure of the film/chip and also focuses the light onto the surface.
The F stop is expressed as a fraction. Thus, "larger" numbers actually mean a smaller aperture. For example, when people talk about "F 16," they really mean f/16, or f over 16. F/8 is therefore a larger aperture than f/16.
These numbers, by the way, are based on a mathematical sequence and they are scaled such that each number down (bigger number but smaller aperture) represents a halving of the light intensity from the previous stop.
Make sense?

What does that mean for me?
The size of the aperture determines two things: 1. The amount of light that reaches your film (in conjunction with your shutter speed, which is next week's topic), and 2. Depth of Field (which is mostly what we will focus on today).

What is depth of field?
Depth of field is a measure of how far back in the frame objects remain in focus.
This is an example of a picture with a shallow depth of field. It was taken with f/5.
You can see here in the example above that detail has only been captured in the lacewing's head. Objects father away from the camera, the rest of the picture, blur softly out of focus. This technique is often used for pleasing artistic effect.
Here is another example:
This picture also displays a shallow depth of field. It was taken with f/6.3
A shallow depth of field allows all attention to be focused on the subject, because background objects are not rendered in detail. This can be advantageous for macro images.
This photo has a greater depth of field. It was shot at f/9.
This photo has a greater depth of field than the previous examples. Note it was taken with a smaller f/stop. A smaller f/stop (eg, f/22) creates a larger, or deeper, depth of field. You can think of this as a small opening focusing the light more sharply, allowing more items in the frame to be rendered in detail. Notice that even items far away from the camera are recognizable. I could have stopped down even farther in this shot to obtain greater detail.

Another example, taken at f/7

What's the deal with the light?
Remember that we said the f/stop affects two things: the amount of light that reaches the film and the depth of field? Well, the farther down you stop (a smaller f/stop, a bigger number), the less and less light reaches the film. This means that your exposure will have to become longer to compensate - and that will be next week's topic (click here to read Part 2 of Photography Basics and here to read Part 3).

Feel free to leave any questions you have below.

Did you see this post about lighting? Check it out!

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