Exposure is the balance of three settings: aperture, shutter speed and ISO. Change one and the others may need to move to keep brightness steady. This sheet shows what each does and how to trade them off.
The Three Settings
| Setting | Controls | Bright side effect | Cost |
|---|---|---|---|
| Aperture (f-number) | Light amount and depth of field | Lower f-number lets in more light | Shallower focus zone |
| Shutter speed | Light duration and motion blur | Slower speed adds light | Blur from movement or shake |
| ISO | Sensor sensitivity | Higher value brightens the image | More visible noise |
The Stop Idea
A stop is a doubling or halving of light. Opening the aperture one stop, slowing the shutter one step, or doubling ISO each brightens the picture by the same amount. This is why you can swap one for another.
- Common aperture steps: f/1.4, 2, 2.8, 4, 5.6, 8, 11, 16
- Common shutter steps: 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30
- Common ISO steps: 100, 200, 400, 800, 1600, 3200
Which Setting to Prioritize
- Moving subject: set shutter speed first, then adjust aperture and ISO.
- Portrait or landscape depth: set aperture first.
- Dim light with no support: raise ISO before accepting blur.
- Bright light and a wish for blur: lower ISO, close the aperture or add a darker filter.
Sample Combinations to Try
Treat these as loose beginnings, not rules. A bright sunny day often works near f/8, 1/250 and ISO 100. A cloudy day might need f/5.6, 1/125 and ISO 200 to 400. Indoors near a window, try f/2.8, 1/100 and ISO 800 or higher.
Never look at the sun through a camera or lens while testing exposure outdoors.
Semi-automatic modes are a gentle way to practice. In aperture priority you choose the f-number and the camera selects shutter speed. In shutter priority you set the speed and the camera chooses aperture. Exposure compensation lets you nudge the result brighter or darker when the camera misjudges a very bright or dark scene, such as snow or a black cat.
Use the histogram on the screen to check balance. A graph piled against the right edge suggests clipped highlights, and one against the left suggests lost shadows.
A handy exercise is to hold the brightness constant while changing the look. Shoot one scene at f/2.8, then f/8, adjusting shutter speed to match each time. The brightness stays similar, but the background blur changes. Repeat with shutter speed and ISO to see each side effect.
FAQ
Should I always use the lowest ISO?
Use the lowest that still allows a sharp picture. A little noise is better than a blurred shot.
Why does my picture look dark in manual mode?
Check the exposure meter in the viewfinder and adjust one setting toward the center mark.
The Short Version
Aperture shapes focus depth, shutter speed shapes motion and ISO shapes noise. Decide which matters most for the shot, then balance the other two around it.