Understanding ISO in Photography
ISO is one of the three fundamental pillars of photography, alongside shutter speed and aperture. It plays a crucial role in determining how bright or dark your photos appear, as well as how much noise (or grain) is present in the final image. But what exactly is ISO, and how does it impact your photography?
Let's dive into what is ISO!
What Is ISO?
ISO (And before that ASA) refers to the sensitivity of your camera sensor to light. A low ISO (e.g., ISO 100) means low sensitivity, requiring more light to produce a properly exposed image. A high ISO (e.g., ISO 6400) increases sensitivity, allowing you to shoot in low-light conditions but introducing noise (or grain in analogous photography).
Think of ISO like adjusting the volume on a speaker:
- Low ISO (100-200) = Clean, high-quality sound (low noise in photos)
- Medium ISO (400-1600) = Slightly amplified sound (some noise, but still clear)
- High ISO (3200-12800+) = Loud but with distortion (more visible noise in photos)
How ISO Affects Image Quality
While increasing ISO helps capture more light, it also introduces noise—a grainy texture that reduces the overall clarity of your image. The goal is to balance ISO with aperture and shutter speed to get the best image quality. It also reduces the dynamic range of your camera, meaning you will get complete black or white sooner from a given scene.
Use low ISO when: ✔ Shooting in bright daylight ✔ Capturing high-detail scenes ✔ You can use a tripod for long exposures
Use high ISO when: ✔ Shooting in low-light conditions ✔ Capturing fast-moving subjects (sports, events) ✔ Flash isn’t available or allowed
Try It Yourself: Adjust the ISO Slider Above
To truly understand how ISO affects noise, use the interactive above. Upload an image and adjust the ISO slider from Low to High to see how noise increases. It is hugely amplified for teaching purposes.
ISO Best Practices for Different Scenarios
Your main goal is to make a usable photo. Therefore aim for the lowest ISO setting that still gives you a sharp image. I have seen plenty of beginners trying to lower the ISO so much that their pictures become blurry. Keep in mind, it's often better to have a wider aperture with lower ISO if your subject allows it.
Here is a small list for ISO (But you don't need to remember it)
- Anything that doesn't move: Lowest native setting. You can compensate by slowing down the shutter speed.
- Daylight Photography: Keep ISO low (50-200) for crisp, noise-free images.
- Indoor natural light Portraits: Use ISO 400-800 when needed. Balance with aperture.
- Night Photography: ISO 1600-3200 can help, but use a tripod to keep noise minimal if some movement isn't a problem.
- Sports & Action: Higher ISO (sometimes >3200) allows faster shutter speeds. Aim for a minimal shutter speed instead of a maximum ISO.
Final Thoughts
ISO is a necessary tool that, when used correctly, can make or break your image quality. With this interactive tool, you can experiment with noise texture and get a deeper understanding of how it works.
Mastering ISO is about finding the right balance. And if you think you shouldn't go above a specific number, think again. It's always better to have a decent picture than to have no picture.