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What is ISO On A Camera? [The Comprehensive Guide]

If you’ve done photography before, you probably came across the term ISO. Now, the basic idea of ISO is, it is a setting in your camera that can be increased to brighten up the photo or be lowered to darken it. What that means is that, when you’re capturing a photo, you can use the ISO setting to increase or decrease the amount of light in it.

Generally, the ISO setting can be handled by the camera itself. But, if you want better control over your photos, you may want to adjust it manually. So, if you notice that your photos are coming out too bright or too dark, you can take control and get the exact exposure you want.

Now, to get a better idea about ISO, you need to be clear about what it is, how to use it properly, and what other stuff in your camera is related to it. So, allow me to familiarize you with the definition, variations, and use cases of ISO, all in one place.

What Is ISO On A Camera?

ISO is the scale of measurement for the Light Sensitivity of your camera. In simpler words, it’s a scale for how much light your camera can/should capture to have the correct exposure in different situations. There is an upper (max) and a lower (min) limit to how much light a camera can capture and the sensitivity measurement of them, defines the ISO Range for that camera.

The image sensors in modern digital cameras need to convert the incoming light into electrical signals for being able to process them. To increase the ISO sensitivity, the camera amplifies that signal, decreasing the required amount of light to take a brighter photo or vice versa in case the ISO level is decreased.

ISO Range & Why It Matters

After getting to know what is ISO in photography, you need to start off with ISO Range and why it is important. To explain why ISO range matters, I first need to explain what is considered as good ISO range. Also, You might be tempted to think that as higher the ISO can go, the better. While that isn’t completely wrong, it is not exactly correct either.

What is ISO Range?

Range is defined from the lowest ISO value your camera can achieve to the highest ISO value it can go up to. For example, an ISO range of 100-3200 means that the camera has a minimum ISO value of 100 and from there it can go up to a maximum ISO of 3200. This is also referred to as the Native ISO range.

Low ISO & High ISO

Now, to be specified as having a good ISO range, the camera needs to have both, great lower and higher ISO ranges. Most of the cameras these days come with a minimum ISO range of 100 while some higher-end flagship devices may go lower at 64 or even 50. Some latest smartphones can even go as low as 25. The brighter the subject/ambiance is, the lower on the ISO scale you should go. 

Low ISO and High ISO

As far as high ISO is considered, as soon you start moving beyond 800, it starts going on the higher side. Although going higher significantly brightens your photo, it can also increase the amount of digital noise. As high as you go, the more digital noise is introduced. Modern cameras can go up to 12800 or 25600 with the extended range going up to 25600, 51200, or even 102400.

Why Does ISO Range Matter?

ISO range defines how your camera is going to perform under extremely bright, regular, and extremely dark conditions. Most cameras do regular situations well but, it is the extreme situations which they might screw up.

For example, if your camera has an ISO range of 200-800, it’ll suffer in extreme situations. If the range is around 100-3200, it’ll perform well in extremely bright situations and decently to kinda bad in extremely dark situations (depends on how dark it is). However, if the camera has a range of 50-25600, it is going to perform excellently in both extreme bright & dark situations. Again, the higher you push the ISO, the more digital noise you’re gonna get.

Extended/Expandable ISO: Explained!

Definition of Extended ISO

Sometimes cameras can push the ISO beyond the native range to compensate for further brightness or absence of light. That capability is known as Extended/Expandable ISO. It generally shows up in Manual ISO Control alongside native ISO.

How Does Extended ISO Work?

As you might have guessed, Extended ISO is applicable on both lower and higher ranges. If a camera supports the feature, it might be capable of lowering the minimum native ISO or increasing the maximum native ISO, or both. For example, a camera might have a native ISO range of 100-12800, but, it might be capable of expanding that range to 50-25600.

Extended or Expanded ISO

Expanded ISO works by increasing/decreasing the exposure stop. For example, if you increase the exposure by 1 stop, the camera might be able to simulate twice the max native ISO. Similarly, by decreasing the exposure stop by 1, the camera might be able to simulate half of the min native ISO. Companies are looking into different methods to use Extended ISO but currently, this is the most commonly used technique.

Practicality & Effectiveness of Extended ISO:

As cool as it sounds, Extended ISO doesn’t really make much sense, at least right now. Lowering the minimum native ISO kinda works as its main purpose is underexposing the shot anyway. But, as brands keep pushing the limit on extending the max native ISO, that’s doesn’t really make much sense.

As mentioned earlier, even increasing your native ISO too much might result in a significant increase in digital noise. Now, when that native limit is pushed further using exposure measures, the image drastically loses quality and the digital noise levels also increase a lot. So, although you’re getting a brighter image, it won’t be as high quality, and in some situations, the images might even be completely unusable.

So, as tempting as those super-high values expandable values like 51200 or 102400 (or even lower values) might sound, it’s more of a marketing gimmick and less of an actual useful feature at this point. Pairing your camera with a wide-aperture lens and staying in the native ISO range works better.

The Relation Between ISO, Aperture & Shutter Speed

As important as ISO is in modern digital cameras, you also need the rest of the software & hardware to comply if you’re gonna get a good photo. Two of the most important things to keep in check here would be the Aperture of the lens attached and the Shutter Speed of the camera.

ISO, Aperture, Shutter Speed

To explain this let’s consider a poorly lit (low-light) scenario. If you have a wider aperture lens (for example f-1.8), it’ll let in way more light compared to a more closed aperture lens (for example f-4.0). So, with that, you can use a lower ISO even in low light. This is because, as the lens is letting in more light, it eliminates some of the need for digitally boosting the light input.

The relation of Shutter Speed and ISO is somewhat proportional. If you want to minimize the light input as much as possible (without changing the aperture), you’d want to set the lowest ISO and fastest shutter speed. As you require more and more light, you need to increase them to an optimal level.

If you have all of these things in auto though, the camera does all of the adjustments for you. But, when you’re on full manual or at least one or two of these settings are in manual, you’d want to get the adjustments done correctly, as that will make or break your photo.

ISO on a Digital Camera vs. ISO on a Film Camera

The concept of ISO in older film cameras is very different from what it is with digital cameras. With older film cameras, ISO was referred to as the film’s sensitivity to light. That had nothing to do with the camera, in which the film’s inserted. Even in this case, a film with higher ISO resulted in grainier photos.

On digital cameras, the situation is completely different. Here ISO is the measurement of the light sensitivity of the camera instead. You may find it mentioned as Sensor Sensitivity in some places but, that statement is actually incorrect. Your camera itself digitally amplifies the light input (converted to electric signals) to achieve the right exposure.

How To Properly Adjust Manual ISO?

Modern cameras come with pretty good Auto ISO capabilities and it’ll do the job really well most of the time. But, diving into Manual ISO has its own perks. A lot of the time Auto ISO will fail to deliver the desired results leaving the photo either overexposed or underexposed. You might even get a lot of extra noise in low-light scenarios.

In those situations, you would want to switch on your manual gears and adjust the ISO to get the precise brightness on your photos. Now, it can be a bit confusing at first but, with proper practice, you can master it pretty fast.

When you have a lot of light at your disposal, you would want to shoot in low ISO. For example, in broad daylight, you’d want to shoot in the lowest ISO setting on your camera. So, in case your camera supports an ISO 100 at minimum, use that. If it can go even lower, then go lower.

However, this changes if clouds are covering the sun. In that case, the lowest setting might feel way too underexposed, so you would want to go to ISO 200 or higher depending on how cloudy the day is.

In low-light situations, you want to shoot at higher ISO levels. For example, in the nighttime, you won’t have access to a lot of light so, you need to use ISO levels starting from 600 to 800 all the way up to 3200 or even higher. Crazy ISO levels like 12800 or 25600 can be used to brighten up the extreme dark scenes, but that’ll also introduce a lot of digital noise.

When you’re shooting in studio lighting situations, depending on how much artificial lighting you have, you need to adjust the ISO accordingly. If there is more than enough light, you can use lower ISO levels like around 100-400, but if the available amount of light is slightly less, you can shoot at a bit higher.

Advantage & Drawback of Auto ISO

Auto ISO or Automatic ISO is when the camera itself decides the optimal ISO depending on the lighting situation of the surroundings. This is extremely helpful when you need to take a quick photo and do not have the time to adjust the ISO manually. Or maybe you don’t like to dive into settings that much and you don’t need the lighting to be that perfect, then keeping it on Auto is what you’d want to do. So, the advantage to Auto ISO is sheer convenience s the camera will manage the lighting situation for you.

However, this doesn’t come without its drawbacks. Although Auto ISO gets the lighting situation right a lot of the time, it often gets that wrong as well. This can result in too bright or too dark photos where the exposure is way off the optimal level. Now, this also happens with smaller inaccuracies, but even in that case, you don’t get the exact result you were hoping for. In those situations, dialing into Manual ISO is the better option.


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