Camera photos look grainy mainly because of a high ISO, too little light, underexposure that you brighten later, or heavy cropping. To reduce noise, give the sensor more light, lower the ISO and apply careful noise reduction when editing.
Why Noise Appears
Digital sensors collect light and then amplify the signal. In dim scenes the signal is weak, so amplification makes random variation visible as speckles. Small sensors, heat during long exposures and brightening dark shadows in editing all add to it.
- High ISO settings amplify the signal and the noise together.
- Underexposed images that you lift later show noise in the shadows.
- Long exposures can warm the sensor and add speckles.
- Cropping enlarges the noise along with the subject.
- Smaller sensors generally show more noise than larger ones at the same settings.
Reduce Noise While Shooting
- Use the lowest ISO that still gives a sharp, well exposed image.
- Open the aperture to let in more light, if the depth of field allows.
- Use a slower shutter speed with a tripod for still subjects.
- Add light with a lamp, window or flash.
- Expose toward the bright side without clipping highlights, since brightening a dark file later increases noise.
- Shoot raw so you have more room for noise reduction.
Reduce Noise When Editing
- Apply luminance noise reduction first, in small steps, and compare at 100 percent.
- Add color noise reduction to remove colored speckles.
- Keep some sharpening so detail does not turn soft and waxy.
- Use masking to apply stronger noise reduction to the shadows and sky and less to faces and texture.
- Consider the noise reduction tool built into your raw editor or a dedicated program.
Know the Trade-Offs
| Method | Benefit | Limit |
|---|---|---|
| Lower ISO | Cleaner image | Needs more light or a slower shutter |
| Wider aperture | More light | Thinner focus zone |
| Software noise reduction | Smooth tones | Can remove fine detail |
| Flash | Adds clean light | Changes the look |
A little grain can look pleasant, especially in black and white, so do not remove it all.
Check Your Results
Compare a few frames at the same size before judging noise. Look at the shadows and at flat areas such as sky, since that is where speckles show first. Print a test or view the image at the size you plan to share, because noise that looks harsh at full zoom can be invisible in normal use.
FAQ
Is grain the same as noise?
They look alike. Grain is the term from film, and noise is the term for digital sensors.
Does more megapixels mean more noise?
Not necessarily. Noise depends on the sensor and how you view the image, so compare at the same output size.
The Short Version
Noise comes from weak light and strong amplification. Get more light, keep ISO as low as you can, shoot raw and use gentle noise reduction.
