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What Does ISO Mean On A Camera: Everything You Need To Know

Published On:
July 26, 2021
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What does ISO mean on a camera? What is ISO in camera settings? What are the functions, benefits, and how to I use it effectively?

These are very common questions among beginner and intermediate photographers. Luckily, we're here to help!

In this article, we'll take a deep dive into what ISO means in photography and how it fits in the exposure triangle.

By the end of this article, you'll have a much better understanding of what ISO is, how to use it effectively, and ultimately be more effective and take better photos because of it!

Without further ado - let's get to it!

ISO Of The Past

ISO is a term that was originally used in film cameras, which represented the sensitivity of film to light (or iso speed). ISO divided the scale of film to be sensitive to different levels of light.

So, the film itself was more or less sensitive to light - meaning the more sensitive it was, the brighter the picture would be once developed.

I'm sure you can see the inconvenience of this. This took skill and experience with different film - you had to know how the film would react to any given scene. You also had to change film if you needed a scene brighter or darker(if shutter speed and aperture couldn't get you there).

Well, digital photography completely changed everything.

So, What Is ISO In Photography

First off, ISO is one of the three points of the exposure triangle. What that means is ISO, when used correctly, will help you make a well-exposed photo (which is the goal of photography).

ISO stands for International Standards Organization (or international organization for standardization), and it's an international standard that each country has adapted to. It represents the sensitivity of a digital camera's sensor to light.

Basically, the higher the ISO number - like 1600 (or 25600 for some cameras these days) means that a camera sensor is more sensitive to low-light situations (like indoors with little to no natural lighting).

This also means you're going to have a brighter picture in those environments because your sensor is now more sensitive to the light that is hitting it.

From an understanding standpoint - ISO is one of the easiest points on the exposure triangle, to understand!

Let's dive a little deeper into how it actually works.

How Does ISO Work

ISO on the other hand amplifies light that hits the sensor. It does this by increasing the exposure reading (and voltage to the sensor) based on your ISO setting.

So, if you take a shot at ISO 100 and another right after at ISO 800 (with the exact same lighting conditions), the ISO 800 shot will be much brighter than ISO 100.

Note: ISO increases the brightness of all sources of light. This would include ambient as well as light created by a flash.

Why Do I Need To Know About ISO On My Camera

Knowing how ISO affects your images is important because it will help you take a well-exposed photo. That means knowing which ISO setting to use for different subjects and scenes.

Too low of an ISO value and the picture will be too dark - too high, and the photo will be too bright.

ISO also offers you a great amount of creative control in regards to how you shoot by allowing you to change the brightness of your shot; from getting a brighter picture in darker settings (higher ISO values), or vice versa (lower ISO values).

Don't forget, ISO is one of the 3 points of the exposure triangle... it's essential to know to ensure you'll get the correct exposure in any situation.

And, you'll run into a situation at some point (if you haven't already) that you'll need to use ISO.

Knowing when and how to effectively use it is what we're going to discuss going forward in this article.

ISO Range

It's incredible how far technology has pushed cameras even in the last 10 years.

To bring 10 years ago into reality - the Canon T3i was dominating the market. We're talking about great photos and acceptable video. It was one of the first DSLR cameras that videographers accepted as a camera that would take video worthy of paid work.

As far as ISO goes - its range was 100 to 6400.

But, anything over ISO 800 was pretty much unacceptable.

Fast forward 10 years and companies like Sony and their A7iii can take very acceptable photo and video at ISO 6400 with a max value of 25600 (expandable to 51,200). Although you'd never want to run ISO at 25k - the option is there if you ever need it.

The ISO range of most cameras manufactured today is 50 to 25,600. This can change depending on the camera and the manufacturer - but this is the average range of cameras on the market today.

What Is Native ISO?

This is the ISO setting that doesn't require any additional voltage sent to the sensor to increase exposure.

Think of this as the 'base level' ISO setting.

You'll also get the most dynamic range out of your camera at this setting.

Lastly (but surely not the least) - you'll get the least amount of digital noise in your images (we will touch on this more here in a minute).

The 'universal' native ISO setting for most DSLR/mirrorless cameras on the market today is 100.

What Is Extended ISO?

The image above was taken at an extended ISO setting of 50 with off-camera flash

Extended ISO is ISO values below 100.

Yes, there are cameras on the market that allow you to go below 100.

This does the opposite of increasing your exposure - extended ISO values decrease (lower) your exposure.

There are claims that photos taken with an iso value below 100 are cleaner and have less noise. I have never been able to confirm this (and I shoot below 100 a lot). I haven't been able to confirm the claim, but maybe you could!

The major benefit of iso values lower than 100 - is shooting with a flash.

Cutting ambient light to create moody photos with flash requires a dark(er) exposure. To get to the exposure I want - I normally have to use a 3 stop (or 5 stop) ND filter and cranking the shutter speed to 1/250.

An ISO of 50 coupled with an ND filter allows me to get the images you see above.

This obviously depends on the time of day and weather conditions - but generally speaking - that's how I (you can too!) benefit from extended ISO.

Let me know of another benefit if you know one!

What Does ISO Affect?

Many beginner photographers that I talk to either don't know what ISO is at all or they're afraid to use it.

Not knowing what it is, is completely understandable. But why would they be afraid to use it?

Well, simply put, ISO affects image quality.

The higher your ISO the more digital noise that's created - and I know you've seen digital noise. Digital noise doesn't look good in most situations (some people like it for nostalgia/stylized photos)

With that being said, I live by two thoughts when it comes to ISO...

Respect ISO, But Don't Be Afraid To Use It

Let's be honest, there wouldn't be a reason to have ISO as an option if it wasn't a viable way to adjust exposure.

So, don't be afraid to use it.

But, don't overdo it! It's easy to 'go ham' with ISO in low-light environments. But get to know your camera, how it deals with digital noise, and make adjustments from there.

Remember, it's much easier to fix a bit of digital noise than it is to fix a really underexposed image.

When You May Have To Use ISO

Let's start talking about when you should (or have to) use iso to get the correct exposure.

Generally speaking, the ultimate 'goal' is to not have to go above iso 100. You get the cleanest looking and the best dynamic range.

But, there are times when you'll have to use high iso. Let's go over a few scenarios now.

Fast Shutter Speed May Require You To Increase Your ISO Setting

If you're capturing fast action (life sports or wildlife) - you're going to have to run a faster shutter speed.

Fast shutter speeds means your images may be underexposed.

Assuming you can't open your aperture any wider (or you want to keep it the same) - you'll be forced to adjust your iso settings.

Increase your iso one step at a time. Meaning, go from 100 to 200 and check your exposure. Trust the exposure meter in your camera and go from there.

This is what's great about digital photography (versus film cameras) - you can see your images right after taking them!

Slower Shutter Speed Indoors

Let's assume you're indoors and have your aperture wide open and your shutter speed is as slow as you can get it without introducing motion blur from camera shake.

You would then have no choice but to increase ISO. Much like the suggestions from the last section, start increasing slowly until your exposure meter tells you it's good.

Trust me, you would have the best image quality by increasing digital iso instead of an even longer shutter speed.

Astrophotography Requires ISO

Astrophotography is probably the hardest version of photography when it comes to balancing aperture, shutter speed, and iso.

It's very easy to introduce too much digital iso (esp considering you can't see the outcome till after the photo is taken on a DSLR).

I recommend introducing iso values as a very slow pace (much like the recommendations in previous sections).

Be prepared to take a series of shots that aren't good - but trial and error will lead to great results.

There You Have It!

I'm sure you can see the pattern in how to approach the use of ISO and how to manage it.

This includes:

  • Only increase iso when you have no other options (aperture and shutter speed adjustments should come first)
  • Native ISO for most modern cameras is 100
  • If all other options have been exhausted - increase iso slowly, checking exposure each step up.
  • Rinse and repeat the process whenever you need to use it!

At this point, you know what iso was, what it is now, and when and how to use it! If you haven't read our other articles on shutter speed and aperture - be sure to check those out as well.

Dive a little deeper and visit our other related articles, What Is Shutter Speed, Aperture: Everything Explained - where you can learn everything else you need to in regards to the exposure trianlge!

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Thank you all for reading and until next time, be safe and keep learning and creating!


What does ISO do on a camera?

ISO is a standard number that measures the sensitivity of your camera's sensor. The higher the ISO number, the more sensitive it will be to light. Typically, you want to use low ISO numbers in good lighting conditions because they produce less noise and are easier to edit later on.

What is a good iso range for a camera?

A good ISO range for a modern camera would be 50 to 25,600. A usable iso range is far more important. Modern cameras are much better at handling iso and digital noise. Brands such as Sony have improved on eliminating digital noise thus making higher ISO settings much more usable. A very acceptable usable ISO range is 50 to 6400.

How does ISO affect a photo?

ISO affects the photograph by influencing the way it is exposed to light. This will also include how the sensor captures the color and brightness of the scene. ISO increases voltage to your sensor thus making the sensor more sensitive to light. Assuming conditions are exactly the same, the higher the ISO, the brighter your image - and the lower the ISO, the darker the image.

Is lower ISO always better?

It depends. Generally speaking, yes. You want to keep your ISO as close to 100 at all times. But, an underexposed shit is almost always better with a little bit of digital noise than a shot with shadows that can't be recovered. Also, small to moderate amounts of digital noise can be removed during editing with little to no issues.
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