Unlocking the Power of ISO for Stunning Photography in Any Light

Imagine this: You’re standing at the edge of a breathtaking sunset, camera in hand, ready to capture the scene. The colors are rich, the light is fading, and you’re kind of desperate to make the most of it. You adjust your camera, but something isn’t quite right—the shot either comes out too dark or too grainy. You feel a sense of frustration, unsure how to balance the lighting to get that perfect image.

This is where understanding ISO can make all the difference. ISO is a powerful yet often misunderstood setting that can transform how your camera handles light, especially in challenging conditions like the one you’re facing. But what exactly is ISO, and how can it help you capture moments like this with clarity and precision?

First, ISO isn’t completely a photography term. ISO is an acronym for the International Organization for Standardization, which sets standards for numerous conditions, including camera sensitivity. You may hear something conforms to ISO – something-number standards, which means that someone took the trouble to write standards and someone else took the trouble to meet those standards. That application is not germane to this use of the term, but it’s relevant in that it’s not what photography ISO is. Photography ISO still refers to the organization, but it specifically refers to how sensitive we allow the image-capturing apparatus to be.

PHOTOGRAPHER, MEET ISO; ISO, MEET PHOTOGRAPHER

Along with aperture (which I wrote about here) and shutter speed, ISO is the third element of the exposure triangle. For digital cameras, ISO refers to how sensitive your camera’s sensor is to light, and it’s a setting that the photographer can control. It’s very different for film cameras, where the ISO sensitivity is controlled by the film the photographer chooses. However, that sensitivity plays the same role in both film and digital cameras. A lower ISO value is ideal for bright conditions, and a higher value is great for low-light situations, but it doesn’t end there. For digital photographers, we can adjust the ISO to compensate for the other exposure factors, the aperture and the shutter speed. When you realize how the three elements operate together, you realize that if the aperture is open wider, or if the shutter is open for a longer time, or both, you don’t need as much light-sensitivity as you would if the aperture were smaller or the shutter was open for less time, or both, to capture an image of the same quality.

It doesn’t end there. The higher settings you may want to use in lower light will introduce “noise,” or grain into your photos, which will reduce the clarity and detail, making it feel just messier. Using lower settings will almost always produce cleaner, sharper images – if you can compensate for the lower sensitivity by adjusting the other exposure elements. There are post-production tools that can help clean up that noise and grain, but they aren’t foolproof and can introduce other issues into an image. It’s always going to be better if you can control that at image-capture time.

Bit of a tangent here: The lower ISO values can also help to maintain a higher dynamic range, which is the ratio between the darkest parts and the lightest parts of the image. It’s going to determine how much detail you’re able to see in the highlights – the brightest parts – and the shadows – the darkest parts. Higher dynamic range means you can see more details at the extremes, and lower dynamic range means you can’t. When a photographer wants to capture those details but can’t do it in one shot, she’ll use exposure bracketing Exposure bracketing is a camera setting, and not all cameras have it. The photographer takes three shots: one correctly exposed, one slightly underexposed, and one slightly overexposed, and does a merge in the processing program. The photographer can set the amount of over- and under-exposure for those shots, depending on the level of detail, the level of shadow, and the level of highlight. Without being able to control ISO, this wouldn’t be possible.

ISO IN FILM CAMERAS

While I can set the ISO level in my camera, back when I was (badly) shooting film, the only way to control that was in the film I chose. I could choose 100, 200, or 400 ISO for the cameras I used. Higher-end, professional cameras had more options, but back then, even if my camera could use them, I wouldn’t have known what to do with them. Most of the time I chose 200 “speed,” although that’s not the accurate term, but it’s what we called it. It was versatile enough for me to grab the kind of shots I was taking. If I knew I was going to spend enough time in early morning or twilight conditions, sometimes I’d use 400, but, truthfully, my photography skills at the time weren’t good enough for it to matter.

The ISO rating for film is determined during the production of the film, and it involves the size and type of silver-halide grains in the film’s emulsion. Traditional grains are mostly roundish crystals that can take on various shapes. They produce finer grain and higher image quality. Higher-ISO films are produced using Tabular grains, or T-grains, which are flatter and more uniform in their shape. The grains are suspended in a gelatin layer which is coated onto the film base. During exposure to light, the crystals undergo a chemical reaction which forms the image on the film.

Since a photographer can’t really swap out film rolls during a photo session, in order to capture images with different ISO levels, he has to have a couple of cameras loaded with the different types of film, and this isn’t unusual for film photographers. That’s just a limitation of film photography that many photographers choose to accept, but having the option to change it on a digital camera means I only have to carry one camera body.

UNDERSTANDING ISO VALUES

Most digital cameras today have ISO settings of 100, 200, 400, 800, 1600, and 3200, and the higher-end cameras extend this to 6400, 12800, 25600, 5120, and 102400. My old Fujifilm FinePix went as low as 64, and my new Canon R6 goes up to 1024000. I took the Canon into the deep guts of Fort Morgan down in south Alabama, and it was able to discern shapes even in some pretty dark rooms, at an ISO of 25600.

In bright daylight conditions, like in the image above, having a lot extra of light hitting the sensor is neither required nor desired. It will wash out the image, overexposing it and leaving you with a light or white box. You’ll use a lower ISO for those days. As you lose light, however, you’ll want to step up that ISO. Cloudy/overcast days can be a challenge, both for you and your camera, because there’s no amount of ISO-shifting that will create a sunny sky in a photograph where none existed in reality. (That’s the job of post-processing.) Going into darker areas will call for even higher ISO values.

ISO AND IMAGE QUALITY

Having the ability to use extremely high ISO means I can get some shots that I would just plain miss otherwise, but at a cost. The camera doesn’t “see” things the way you and I do, because the camera’s sensor is not an eye. It’s an electronic component that relies on electricity passing through circuits. When I pump up the ISO, the signal from the sensor to the Analog-to-Digital Converter (ADC) is amplified. That signal is actually an electrical charge, and boosting that signal introduces more static, which is what creates that “noise,” the grainy stuff you see in darker photos.

The image below was taking in Cathedral Caverns with my PowerShot (I can’t remember why I chose to use that one for this tour, but I did). I did set the shutter speed to manual at 6/10 seconds, and the camera adjusted the aperture to f/8.0 and the ISO to 1600.

It did a decent job of capturing the stunning shapes, but if you zoom into the dark area, you’ll see some of that noise.

WHEN TO ADJUST ISO

Sometimes – well, most of the time, actually – the camera does a decent job of deciding what settings to use. When I’m out documenting an event or capturing memories, I almost always let the camera do the choosing. Thanks to that preview screen, I can tell if it’s doing what I want it to do for me. If it’s not, I need to figure out what it doesn’t understand. Is the light lower or higher than the camera thinks it is? Is the camera unable to make the balance between an object in motion and the light condition? Many cameras, even higher-end point-and-shoot cameras, have “program” modes that anticipate the requirements for particular situations. For example, my Canon PowerShot has several modes: sunset, fireworks, landscape, portrait. The camera has a range of preset settings for each of those situations.

However, if you’re trying to be a little more creative, you can try changing ISO to see what it does for the shot, and then you can bring in the other elements (shutter speed and aperture) to play with the exposure as well. We generally want to use the lowest ISO that will capture the shot, because of that noise factor. As a result, you want to start at 100 or 200 and see if you can get the exposure right by adjusting the shutter speed (slower shutter speed to let more light in over the course of the shot) or aperture (wider aperture to let in more light). These can also present unexpected consequences. For example, with a slower shutter, you have to be careful not to move – a tripod helps here, but I’ve also braced myself against something and held the camera as still as I could. Opening the aperture may be a better option if depth of field isn’t a concern. You’ll just have to play around and see what you get. This is something you want to get really familiar with so that you can make the call on the fly, like when you’re on a cavern tour and have five seconds to get the settings and get the shot before the tour moves on and you’re left all alone.

HERE ARE THE GENERAL “RULES”

Feel free to break them and see what you get.

• Landscape – Low ISO
• Action – Higher ISO
• Night or dark environments – High ISO

YOUR TURN

I’d love to hear about your photography journey. ISO is one of the most challenging elements for me, because it’s usually just a short hop for me from underexposed to overexposed. I’m still learning, though, and I do expect it to get a lot better. Did you learn something you can use from reading this, or was there something I could have explained better?

Also, here are some links to some more great articles to give you even more information:

How do I choose the right ISO for film photography (learnfilm.photography)

How Does ISO Affect a Photo in Photography? (ISO Explained) (worldoftravelphotography.com)

What is ISO? Understanding ISO for Beginners – Photography Life

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