The Wild Photographer

What's the Deal with ISO (and why you should care...a lot)

• Episode 63

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ISO is one of those photography tools that feels like a superpower… right up until it bites you. In this solo deep dive, Court unpacks why ISO is both a “magical unicorn” and a ruthless double-edged sword: it can rescue your shot in low light, but it can also quietly inject noise and crush editability.

You’ll learn what ISO actually does (and what it doesn’t), how to think about it in terms of light and "stops" and how to use it strategically in the field—especially in the real-world low-light scenarios we all love to shoot. Court also shares his go-to ISO workflow, how to set guardrails so your camera doesn’t go rogue, and why modern de-noise software changes the risk/reward equation—but doesn’t eliminate it.

If ISO has ever felt confusing, intimidating, or like the setting you touch only when you’re desperate… this episode is your new playbook. 

Expect to Learn:

  • What ISO is (in plain English)
  • ISO as part of the Exposure Triangle
  • Stops and ISO math (the simple rule)
  • The tradeoff: noise + reduced editability
  • Manual ISO vs Auto ISO
  • Avoiding Auto ISO “oops”
  • A field-friendly hack: slight underexposure
  • De-noise software: powerful but not magic
  • Two mechanical ways to keep ISO lower

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Court Whelan (00:00)
ISO is this silver bullet, this magical unicorn in photography. I love it. It's one of the most incredible tools we have. I also hate it because high ISO can really degrade a photo. can make it less editable. It can add noise and grain. It really deteriorates a photo. So ISO is this double-edged sword where it's an amazing thing. We can shoot in lower light than ever.

but we have to be just as careful as ever because even though we can go to hire ISOs, the noise and grain is still there. so today's episode is all about ISO. What's the deal with it and why you should care a heck of a lot about it. Before we get into the episode, wanted to thank our sponsors.

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Great company to work with lensrentals.com. Okay, so let's dive into the episode now.

What is the deal with ISO and why you should really care about it? So first up, let's talk about the word or the term ISO. What does it mean?

Well, ISO, it's an acronym, but it doesn't stand for anything really specific camera related. It's actually an acronym for this International Standardization Body of Measurements. And these are the same folks that make sure that the measurement of a bolt or a screw or a light fixture is set to universal standards. They just also happen to govern this camera light sensitivity as well.

So don't worry about exactly what ISO spells out or the terminology there. I want to tell you more importantly, what it does in your camera. So ISO works in a very unique way and it ultimately allows more light sensitivity in your camera. doesn't actually allow more light in your camera. That's an important distinction. So aperture, that opening of your lens, physically lets in more light. ISO just makes your sensor more sensitive to light. Okay, so very, very important distinction there.

However, what it does for you is very, very similar to what aperture and shutter speed would do if you're letting in more light. So the basic gist is that when you crank your ISO up and it acts in units of like 100, 200, 400, 800, every time you double it, you're actually doubling the amount of light that is getting into your camera.

And it does so by a very unique process. Essentially what it does is it sends a very small electrical signal through your camera's sensor that does make your sensor more sensitive to light. Okay. Now this is a great thing because we can increase the amount of light coming into our sensor. might be dawn in the Serengeti. It might be deep in a rainforest and our photo is just too dark. We're having to shoot at far too low of a shutter speed or we're having to dial that aperture

to a really, really small F number, even though we want a big depth of field, or maybe your lens doesn't go below F 7.1 or F 5.6, and we're kind of stuck at that as our quote unquote maximum aperture. ISO is once again, this silver bullet, this magical unicorn riding in to allow us more light into our camera's sensor.

And it does so through this little electrical pulse. Okay, so it's a great thing because we now have this tool to increase the amount of light. However, there is a very strong negative in that the higher the ISO goes, the more noisy or grainy the photo becomes. You may have heard these terms, noise and grain are kind of the same thing. It's essentially different colored pixels that just pop up somewhat randomly in your scene, or it might look like you took a printed photo.

and just rubbed some sandpaper on it a little bit. It's just kind of rough, it's textured, it has this noise in it that is very, very undesirable. You generally do not want noise ingrained in your photography. There's this little trend, especially on social media right now, where ⁓ people are manually injecting noise to give it that vintage look. And in older cameras, this is very, very similar to like ASA film ratings. When you had those higher film ratings like ASA 800, 1600,

they would look a little bit more noisy and grainy and that was just kind of a look from yesteryear. In the age of digital photography, we tend to not like that look. It looks less clean, it looks less sharp,

But more importantly, as this ISO increases, we just can't edit the photo as much as we normally would before it starts to get really, really degraded. So I'm going to talk a little bit about what a high ISO actually means. It's very subjective as a high ISO 400 or 800 or maybe 6,400. What do these numbers mean? But I do want to come out the gates with this strong benefit that you are able to increase the amount of light perceived by your sensor with essentially the click of a button, the turn of a dial.

but you do have this negative that it can degrade your photo as it goes

it's, there's usually a threshold in most cameras and most people's let's just say tolerance above a certain ISO where the photo just starts to look bad.

okay, so ISO works largely in the same kind of terminology as aperture and shutter speed. In fact,

When we talk about aperture, shutter speed and ISO, we usually refer to them as what's called the golden triangle. If you want to keep exposure the same, meaning the same light and dark in a scene, if you change one of these, the others have to adjust. So

have this terminology of a stop of light. And what a stop, STOP of light is, is essentially doubling or halving the amount of light. So I'll give you an example. If you're shooting on

a steady aperture and a steady ISO and you go from one hundredth of a second to one two hundredth of a second of a shutter speed, you are having the amount of light instead of one hundred. It's one over two hundred. OK, so exactly half. That's one stop of light. Now, that would be one stop of light in the darkening direction or in a faster direction. The other stop of light could go the other way and you can go from one over one hundred to one over fifty. So you.

halve the shutter speed and you double the amount of light. And aperture works in a very similar way. It's not as linear as shutter speed. And as you'll see in a second, as you'll learn in a second, it's not as linear as ISO, but aperture, if you're at F 5.6, you will double the amount of light going down to F4. You will halve the amount of light going from F 5.6 to F8. So this is not the episode to go into a deep dive in aperture and shutter speed. have other episodes on that. I'll encourage you to listen and check those out.

But ISO, what I like about it is it is more linear. So just like shutter speed where you can do quick math of, you know, what is one half of 100, okay, 50. That means I'm doubling the amount of light. It's a longer time my sensor is open to let in more light. ISO works the same way. And so every time you double ISO, you are letting in twice amount of light. Okay, I'm gonna say that again. Every time you double the ISO, you are letting in twice the amount of light.

So as you can imagine going from 200 to 400, you double light 400 to 800, you double light 800 to 1600 and so on and so on. You are doubling light every single time. Okay. So every time you double that light or have the light, you are going one or the other direction by way of stops. That is one stop. the applicability here is that if you're on a photo trip and your guide is saying, Ooh, I would let in another stop of light here because it's just really, really dim.

that means you want to go ahead and double your ISO. Okay, so going from 400, if you are going to let in another stop of light, that means boom, ISO 800.

so next up, how and when to set your ISO. You can do this in a couple of different ways. The traditional way is to manually set it. You have your ISO in a menu system, you have it on the back of your screen, you tap it or you dial one of the dials and you increase or decrease ISO based on your settings. And this is fine. This is how we've had to do it for a long time. But in the last several years, auto ISO has made significant improvements.

such that nowadays you can do this technique. This is what I use for 95 % of my photos is you can actually shoot on full manual plus auto ISO. And this is a great technique where you set the aperture, you set the shutter speed, but then you let your camera choose the ISO for you. And this is wonderful because we usually have an idea of aperture, right? That's gonna be our creative vision for how much blur or how much is in focus, what our depth of field is.

We also usually know if we need a faster, a slow shutter speed, or if we just have to set our camera at the minimum shutter speed to prevent hand movement. usually what I'm thinking about ISO is when I'm in challenging lighting conditions. think dark, dim rainforest under the canopy. Think really early morning safaris. This might be in Alaska. This might be on the tundras of Canada looking for polar bears. And it's just low light. It's beautiful light, but it's low light.

planes of the Serengeti, you're getting that nice, soft, angled, real yellow-orange light. These are some of the best times of day to photograph nature, wildlife, landscapes. However, you have this very real challenge of there not being as much light in the ambient atmosphere as, say, three hours later, right?

So as a result, I'm hyper focused on ISO because I really can't change aperture and shutter speed all that much once I'm at their minimums. Let's use an example. So I'm photographing a lion in the Serengeti. I'm on my 100 to 400 millimeter lens and I can't go below f5.6, meaning I can't go to f4. The lens will not let me. It's not a good enough lens or it's not a big enough lens. So then I'm thinking my shutter speed. Okay, so this lion is

moving, it's walking, I'm gonna need to set a certain shutter speed in order to freeze that movement, assuming I'm not going for any sort of intentional motion blur, But I know I need to shoot at something like one over 250, one over 320, something in that range. So then I'm putting auto ISO on my camera and letting the camera figure out, okay, to get this aperture, to get the shutter speed,

my ISO has to be X.

the next way you can do this is you can go ahead and dial in ISO on your own, not use auto. And this is fine. This is no problem. It does take a little bit of extra time. It's one more thing to have to manage and monitor and deal with. I've personally found that by shooting in auto ISO mode, there's a couple of big advantages. One, my camera usually gives me a lower ISO than I would have surmised on my own, than I would have guessed. And that's a good thing. Remember low ISO is always a better quality photo.

The other thing that I've found is that I can actually shoot a lot more shots because I'm not having to manage this thing. I'm not having to think about it. The third thing is that I can actually quickly adjust my exposure based on stops using my exposure compensation tool. And so this is a little tool on your camera that has a little plus or minus symbol and you can dial it left or right and just quickly add or remove light from the scene.

And so if you just wanna quickly increase or decrease the exposure of your scene, there's usually a dial or a button on your camera, oftentimes linked to that little plus or minus symbol. And the camera, by having auto ISO, will just adjust ISO for you.

So this is fantastic. Now the problem here is that if you go willy nilly and just shoot at a super fast shutter speed or have a really deep depth of field for low light conditions, your camera, if it's deciding auto,

ISO for you,

it might ramp it up so high and you might not realize it and you're shooting at like ISO 12,000, 25,000, multiple shots, multiple scenes and realizing, oh my gosh, these photos are just gonna be no longer usable. So what is an appropriate range for ISO? Well, to me, I have a full frame mirrorless camera and I personally find I'm able to go up to about

ISO 6400, ISO 8000 without having much degradation or what degradation in the image there is, I can deal with by denoising it in Lightroom or Camera Raw. We'll talk about denoising in a bit. For different cameras, you have different thresholds. If you have a small point and shoot, you're gonna see noise probably over ISO 400 or 800. You have a lower threshold. If you are in a crop frame sensor or a more introductory camera, you are going to see that

issue appear at ISO 800 or 1600. So this is one of the major gifts, one of the major advantages of full frame cameras and one of the major advantages of keeping up with the latest camera tech because as those sensors improve, you are going to have a higher and higher ISO threshold such that you can shoot at high ISOs and get the same photos as low ISOs on older cameras or more inexpensive cameras. So

There are a lot of reasons to upgrade to a full frame, but this is by far and away my number one reason why I shoot on full frame is I have so much more leeway when shooting in low light conditions. So the range of ISO, the best thing to do is to look at some YouTube videos and some tests, or create your own tests. Go out in conditions that you normally shoot in.

and take photos at 200, 400, 800, 1600, 3200, 6400, put them on the computer, start zooming in and seeing where do you notice a little bit too much noise and grain. So if you can think about the advantage of a bigger, better full frame camera, if you can go,

to ISO 6400 and meet that threshold versus a different camera and topping out at say ISO 3200, I now have twice as much light I'm able to get into my camera sensor than the other option, than the alternative. And that can be huge. It's not huge for shooting in midday conditions. It may not be huge for shooting if you're using a flash or if you're doing, know, tripod work and landscape photography, but if you're doing a lot of wildlife stuff,

If you're doing a lot of fast moving stuff, if you're shooting in low light conditions, having the ability to go twice as much light is a very, very big game changer. And so something you can do, if you do choose to take my advice on the full manual mode with auto ISO is you can go into your camera's menu and actually tell it the range, the upper limit that you would like to reach with your ISO. Meaning you can tell it, I don't want you to go above ISO 3200.

when choosing automatic ISO because that's going to set your camera's limit so that you don't get those bad photos. Now, what you're going to see is your, you know, let's just say the light is dim enough that your camera would have chosen to go higher if it was permitted is you're going to notice your photos are darker than you'd like because again, it tops out at that certain ISO that you set it at and without changing shutter speed or aperture, you will get a dimmer photo and that's okay sometimes.

you know, that's not necessarily a bad thing if that's your limit and your threshold. But one other option, this is another reason why I really like that exposure compensation meter, is that sometimes when I am in dim conditions, I will actually dial my exposure to minus one third, minus two thirds of a stop, just to A, buy me a little better ISO, so my camera doesn't have to go quite so high.

But also let's not forget that in dim conditions, we kind of want to portray that dimness. know, to get a fully even exposure at 5.30 AM on the Serengeti is not going to be realistic. It's not like what your eyes saw. Your camera is trying to choose an even exposure based on, you know, this magical 18 % gray pixels across the scene. That's actually a real thing. It's choosing a very, very digital proxy for what an even quote unquote exposure is.

So a great hack having to do very intimately with ISO is in those dim conditions, you can dial your camera's exposure down just a little bit by one third, two thirds of a stop, and that will ultimately yield a lower ISO because it doesn't have to let as much light in your camera. Now there's one thing here I want to warn you against is that ISO tends to be most visible, or I should say the grain and noise of high ISO tends to be the most visible.

in dark photos. Okay, so you want to be careful with this balance of not just under exposing everything with a high ISO because that grain and noise is gonna be a lot more visible. You can try this out. You can go photograph some night scenes and see what it looks like with ISO 3200, 6400 when the sky is predominantly dark. That noise is really, really expressed.

So it's worth noting that high ISOs tend to look the worst in really dark scenes, which is very unfortunate and borderline counterintuitive in the sense that

ISOs in dark scenes. So, know, like what gives, man, right? That's the time you need it. So you're telling me it looks worse in those scenes? Well, yeah, that's just how cameras work. it's a very, very important

important thing to think about, do not treat ISO lightly. I look at it as this wonderful, magical silver bullet that allows me more light, but I know how quick it can turn a photo from great to just mediocre. But here's where you can get into a little bit of another hack, and this is denoising software. So in all the major camera editing platforms like your Lightroom, your Camera Raw, the full Photoshop,

a third party program like Topaz de-noise These are all programs that have really advanced de-noising capabilities and de-noising is basically the ability to go in, hit a button and the software magically looks at your photo and removes that grain. It's

pretty amazing. It's getting better with every new version of software. So every new version of Lightroom has better capabilities here and it is a game changer. Let's be honest. It's a really, really big game changer. I'm often faced with the question. Do I denoise all of my shots or do I denoise all of my shots over ISO 1600 or 3200? And the answer is no. And this kind of goes back to what I was talking about before in that dark shots tend to look

the most noisy and grainy. So there's a little bit of subjectivity there. In addition, I may not be so sensitive to noise and grain for every single shot, especially in daylight conditions, especially with very busy scenes. it's a wildflower filled meadow with mountains and snow and dappled clouds, you're really gonna see the noise and grain most when you have a lot of even colors and textures.

and even lighting. again, when we're thinking the night sky, when we're thinking the blue hour, when we're thinking, you know, very minimalist photos, that's when noise and grain is going to appear the most. So I don't have to do denoising for all of my shots. Now you might be asking, well, what's the risk? There actually is a downside to denoising. Denoising is going to basically forcefully unsharpen your photo to remove all that noise and grain, and then it's going to resharp and select parts of it. So I'm going to say that again.

to de-noise, actually is this two-fold process of unsharpening and resharpening your shot. And it works really well a lot of the time, but the idea of unsharpening and resharpening can be bad for certain shots. And I can't give you a perfect playbook on which shots it's good for and which shots it's bad for, but I've noticed that I really prefer to look at each photo individually, figure it out if the noise is within my tolerance. Sometimes,

a 3200 ISO shot on one scene is a little bit too bad for me, yet an ISO 8000 scene is just fine for me. So it's not completely across the board that I would do any sort of major adjustments or systematic workflows. I do treat each photo on its own.

So the last thing I'm talk about is how to improve your ISO with mechanical abilities. And what I mean by that is you can get a lower ISO

in two different ways. You can either get a much faster lens as they call it. So a faster lens would mean it has a lower F number at its quote unquote maximum aperture. I realize aperture terminology is very confusing, but the basic gist is that if you have a low F number, that's considered the same thing as having a very big maximum aperture because those low F numbers have a very big opening to light through your lens to your sensor. So one thing you can do

like again, let's picture Dawn on the Serengeti, is if you're finding that your ISOs are just far too high, you might need for your next trip or for the rest of your photo career, think about faster lenses. If you prioritize times a day or scenes or regions or wildlife subjects or landscapes that are just typically very dim, like that's when you like to shoot, that's when you think your best photography is happening.

you might want to get a faster lens. And this is not a light decision because, light, yeah, pun intended. This is not an easy decision because faster lenses are really quite expensive. So for instance, the Canon 100-500, very classic zoom telephoto lens, very sharp. It has a maximum aperture at 500 millimeters of F7.1. That is...

not very fast, that is going to give me a high ISO because it doesn't let in nearly as much light as a lens that would have a max at f4 or f2.8. But just to give you an idea, the commensurate lens, if I were to go to a 600 millimeter f4 by Canon, it takes a lens that would cost $3,000 and turns into a $14,000 lens. So.

I wanted to put this out there as it is indeed an option. It's something that I covet. but they are very, very expensive and they're very, very big. They're hard to travel with. Even if I was given one of these lenses, I would often have to scratch my head as to whether I wanted to bring that big bazooka and have to lug it along and have to balance it and try to handhold it and consider bringing a monopod, et cetera, et cetera, or just have the much more travel friendly version, which is usually that zoom telephoto.

with not as great of an aperture. Now the other thing you can do is you can stabilize your shots. such that you can shoot slower shutter speeds. Remember, we're talking about this golden triangle. So a good way to reduce your ISO, whether you're setting it or it's on auto, is to shoot at a slower shutter speed. That's another way it lets more light in your camera, right? So you can do that if you're shooting a landscape shot.

by putting your camera on a tripod, plain and simple. This is something that I do often for sunrise, sunset photography, but also just kind of dawn in the mountains when I wanna capture that Alpenglow, when I wanna capture big fields of wildflowers with big deep depth of fields, when I wanna photograph that starburst effect and I'm shooting at F22, a tripod is one way to lower my shutter speed as long as my scene is not moving.

like the mountains aren't moving, you can shoot at a very slow shutter speed. And oftentimes I'm able to get down to something like ISO 100. That's fantastic and phenomenal. That's like the best ISO you can get. There are some times you can go lower to like ISO 50 on certain brands and cameras, but ISO 100 is sort of the pinnacle. That's your highest quality photo.

So that's just a really good trick out there. Now it doesn't work if you're photographing wildlife that is moving. You have to have really sedentary wildlife to shoot it one 10th of a second, even on a tripod and one 20th of a second. So it's a bit of an issue if you're not photographing landscapes, if you're photographing people in dim conditions, that's another thing where a tripod isn't gonna help a whole lot. But again, tripod is really, really great for ensuring a low ISO in those conditions.

and if you don't have the ability to get that bigger aperture, i.e. lower f-number,

your only real recourse here.

Okay, so there we go. A full deep dive into ISO. So we talked about, what it is. It's this electronic pulse that goes through your sensor. The good part is that it lets in a lot more light by your sensor, but it adds noise and grain. We usually think of ISOs as this very linear stop wise equation. So as you go from 400 to 800, we are increasing light by a stop, brightening our shot. As we go from 400 to 200, we are decreasing by a stop.

The range is very, very subjective. I highly recommend you consider doing some experimentation or reading some articles about your exact make and model of camera body. But generally I think that the best ISO is 100, 200 is not much worse, even though you double the amount of light. So 200 is one of my best lower numbers. I rarely try to get to 100 unless I'm using a tripod.

but 200 to roughly 3200 is a pretty safe sweet spot for most modern cameras. If you go for the bigger, better full frame cameras, you can probably double that one more time to 6400, but setting a range in your camera can be helpful. I'll be totally honest, I do not set that range myself. I set it all the way to 25,000 because I know that if it's a really great shot that I have to get, that I have to have a certain shutter speed for, I have to have a certain aperture for,

I'm relying a little bit on de-noise in my programs afterwards. So de-noise is definitely there as another layer to the silver bullet equation. de-noise will rescue your shot even at high ISOs, but I do not rely on it. I always try to get the lowest ISO possible given the conditions. And remember that ISO is a tool. You really have to think about shutter speed and aperture first and foremost.

ISO is coming in to the rescue to allow you to shoot at 1 over 320 if you need to to stop wildlife movement So at the end of the day I do advocate for using ISO even high ISOs to the best of your ability Because you really have to think about what are you trying to do with your photography? Are you trying to get that deep depth of field? Are you trying to freeze motion and ultimately ISO is that magical way that very very effective way?

to have your cake and eat it too, oftentimes when it comes to light and photography. Thanks very much and talk to you next time.


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Court Whelan

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