Most photographers try their absolute best to avoid ISO noise in their photos and some spend an age trying to rid their images of it in image editing software. But it's not as much of a problem as you think and here's why.
The general rule of thumb is that the higher your ISO sensitivity is, the more noise you get. If you don't know what I mean by noise, it's those little gritty granules that pop up all over a photo when you've bumped that ISO up. It normally occurs in low-light situations because photographers are trying to maximize the light sensitivity of their image sensor in order to attain certain aperture and shutter speed settings. By boosting the ISO up high you can keep the shutter speed fast which means sharper images when shooting moving subjects or when capturing shots handheld.
Alternatively, it could be so that you can maintain a narrower aperture if there's less light available, as you may want to maintain a specific depth of field to keep slices of your subject in focus, this is especially important on longer focal lengths as the perceived compression of the shot reduces the depth of field dramatically as you reach the telephoto range.
The rule of thumb is to keep ISO as low as possible to avoid the noise interference. That's because a lower ISO gives less noise and reportedly a better dynamic range/clarity in the shot. However, the technology in modern digital cameras is so sophisticated that high ISO noise is much less of a problem. There are noise-handling algorithms built into the camera's processing that aim to specifically reduce high ISO noise and help to keep it uniform and minimal across the entire frame.
This improved ISO noise handling comes in handy when image editing in Lightroom for example, because removing noise that is uniform across the image is much easier than editing a shot with patches of noise (such as in the shadowy parts of a frame). With a swift de-noise filter you can turn down the volume of noise across the entire frame, maintaining detail in the scene at the same rate, rather than removing it harshly from one area and hugely affecting the details in a spot that doesn't have a noise complaint.
Let me show you what I mean, below is a shot taken on a seven-year-old Nikon D750. One is taken at ISO 4,500 and the other ISO 12,800.
Notice much of a difference? No, me neither. And this noise-handling technology is seven years old. Processing power and in-built firmware processing have advanced massively since then so you can happily shoot ISO in its thousands if not tens of thousands without issue.
That said, it's all about balance. Keeping an eye on your exposure triangle and trying your best to balance all three settings is crucial to minimizing ISO noise and should be your first port of call to avoid noise in the first place. But even then, image editing software is incredibly useful for removing a lot of this interference if you do suffer from it. All I'm going to do is import the photo into Lightroom Classic, head to the detail panel, and up the Luminance slider slightly while adding in a little from the Detail slider to preserve details in the face.
"Does this really make a difference?" I hear you say. Well, look at a super close crop of the image, we're able to preserve the details in the eyes, nose, hair, and rest of the face whilst also reducing the noise in the shadowy areas on the right of the image. Bear in mind this is ISO 4,500 and we can edit shots to look like it was shot at a much lower ISO.
Lastly, I should say this: who cares if there's noise in it? Does it really matter? Some of the most famous and influential photographs in the world have plenty of noise. Have a look at Jeff Widener's "Tank Man" or "Alan Kurdi" by Nilüfer Demir, neither of those shots are completely pristine as you might expect from, say, a commercial studio shooting fashion, but it doesn't matter. It's about the photographic content, the subject matter, and how you want to portray your scene.
Of course, it completely depends on what the intended outcome is. If you need a photo that is crisp, clear, and technically perfect then perhaps shooting at high ISOs won't help you. Timing is another important factor when it comes to shooting with high ISOs or not. If you have all day, or several days to set up a shoot, light it, style it, meter the light, test shots, and more, then you might be able to afford a lower ISO. However, shooting something live, off-the-cuff, or documentary style you might find that isn't possible. There's also the expected quality from the viewer that matters. Live music, concert, and gig photography - all known to be taken in low light situations and so the viewer assumes that it might be noisy, gritty, punched with textures, and so on.
If you're a photographer who's worried about high ISO noise, or photo noise in general, there's a few tricks you can do to stabilize yourself so you don't end up worrying unnecessarily. Go through this checklist:
- Can you see your subject clearly?
- Is your subject/scene sharp where you intend it to be?
- Does the noise in the photo obscure details which you deem important in the photograph?
- Zoom out to a thumbnail, is the noise still noticeable?
- Compare it to similar professional images online — is the noise much worse?
- Can you do anything to correct it in image editing?
- Make the noise worse in an image editing software, look at it for a while, then remove it, are you now happier with it?
Hopefully, with that checklist complete you can focus more on the subject and the scene rather than the technical grit that comes with ISO noise. It should give you the opportunity to lay off yourself if there's some ISO noise in your shots, give yourself a break, and keep shooting.