Exposure / Learn by doing
F-stop explained simply
What is “F-stop”?
A number describing the size of the lens opening relative to its focal length. F/2.8 is a wider opening than f/8.
- 01f/4
- 02f/5.6
- 03About half the light
How do you use F-stop practically?
A small exercise
Compare f/4 and f/5.6 on the same lens. F/5.6 admits about half as much light, so compensate with shutter time or ISO.
- Make a starting version and keep it so you can compare fairly.
- Try the change in the exercise. Keep unrelated choices steady where the exercise allows.
- Compare the result at the size your viewer will actually see. Write down what changed and whether it helped.
How does F-stop solve a problem?
F-stops give photographers a shared way to discuss exposure and depth of field.
What can go wrong?
A bigger f-number means a smaller opening. It does not mean more light enters the lens.
How do you turn the idea into a useful solution?
Start with the specific problem in your image or brief, try the exercise, and keep the version that meets that need. If the result is worse, return to the starting version and change one choice at a time.
Quick check: can you explain the three ideas in the diagram?
f/4 → f/5.6 → About half the light. Explain how each relates to the exercise. Then compare the starting version with your result and choose the one that meets your brief.
Related video lesson
Exposure basics — Canon
This related lesson gives wider context for the topic. Camera menus and software versions may differ from yours.
Loading the player connects to YouTube. You can also watch the lesson on YouTube.Keep exploring
Try the idea in a studio shoot
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