You're not alone if you've ever boosted exposure during editing only to discover excessive noise in your photos or videos—despite shooting with a low ISO. Many creators have been misled by the idea that a lower ISO automatically equals less noise. Let’s explain why this happens and how you can adjust your approach for cleaner, higher-quality images.

Understanding ISO and the Noise Floor

ISO is a camera setting that digitally amplifies the light signal captured by your sensor. Unlike optical adjustments (like aperture or shutter speed), ISO is an electronic modification that boosts exposure within the camera. While increasing ISO can introduce noise, simply keeping ISO low isn’t the solution—it’s more nuanced than that.

Here’s the key: The noise floor is your camera sensor's baseline amount of noise, regardless of ISO. It’s most noticeable in the darker areas of an image. If you underexpose an image by lowering ISO and then boost the exposure in post-production, you effectively raise that noise floor along with your exposure, resulting in a grainy, degraded image.

Why Underexposing with Low ISO is a Mistake

Many photographers and videographers believe shooting at the lowest possible ISO is always better. But when you underexpose your image in-camera, you leave critical details in the shadows once you boost the exposure in post-production; that initially hidden noise becomes glaringly apparent.

To illustrate, imagine this scenario:

At ISO 3200, a properly exposed image may show some noise, but it’s manageable.
At ISO 100, an underexposed image appears clean in-camera. However, boosting its exposure during editing reveals far more noise than the ISO 3200 shot. The shadows lose detail, and the overall quality deteriorates.

This is because when you underexpose, you’re not capturing enough light for your sensor to work with, forcing the noise floor to rise when you adjust later.

Finding the Right ISO Balance

To avoid excessive noise and retain detail:

Prioritize Aperture and Shutter Speed: Start by opening your lens aperture as wide as possible to let in more light. Lower your shutter speed if movement in the scene permits.
Use ISO Strategically: Gradually increase ISO until the exposure in-camera is correct. Modern cameras handle higher ISOs exceptionally well, so don’t fear using them for proper exposure.
Expose Correctly In-Camera: A properly exposed image with a slightly higher ISO will always look better than an underexposed image shot with a low ISO and corrected later.

Examples: Low ISO vs. Proper ISO Exposure

Let’s look at two examples to demonstrate this concept:

Proper ISO Exposure (ISO 3200): In a scene shot with ISO 3200 and proper exposure settings, noise is present but controlled. The image retains detail, sharpness, and accurate colors.

Low ISO Underexposed (ISO 100): A shot at ISO 100 but underexposed in-camera produces severe noise after exposure is boosted in post. The noise is far worse, and the overall image quality suffers.

Modern Cameras and Noise Handling

Today’s camera sensors are incredibly advanced, handling higher ISO levels with minimal noise. While noise can still appear in extremely low-light situations, proper exposure minimizes its impact.

Here’s what you should keep in mind:

Always expose your image correctly in-camera, using the exposure triangle: aperture, shutter speed, and ISO.
Don’t hesitate to raise your ISO if needed—it’s better to capture an image with manageable noise than one ruined by underexposure.

Final Thoughts

Using ISO correctly is a game-changer for creating professional-quality photos and videos. Don’t fall into the trap of always shooting with the lowest ISO; instead, embrace the tools your camera provides. When you expose your image properly in-camera, the results will speak for themselves.

If this post helped clarify ISO, consider subscribing to my YouTube channel for more photography tips, gear reviews, and tutorials. Let’s create better images together!

Until next time, happy shooting!

ISO Mistakes You NEED to Avoid