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What is ISO?

10 min read

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What is ISO

The acronym ISO refers to International Standards Organization. This gives us absolutely no clues as to how it is relevant in photography. The ISO setting on a camera controls how responsive the camera’s sensor is to light. This is universal across all brands and types of cameras. ISO settings are the same on phone cameras and on all types of film for film cameras.

The term ISO has been around since the early film photography days, but why is it still relevant in the digital age? ISO is one of the most important camera settings in digital photography

Along with shutter speed and aperture controls, different ISO values have an effect on the exposure of a photograph. So when you want to capture images that are well exposed, the ISO must be managed effectively.

Making Good Use of ISO in Photography

The ISO setting is one control on a camera that allows you to control how bright or dark a photo is. The other two are aperture and shutter speed. A high ISO setting means the sensor is more responsive to light. A low ISO setting has the opposite effect. So, in bright light, use a low ISO setting. When the light is low, use a high ISO rating. 

Choosing the right ISO for the lighting conditions will help you maintain a fast shutter speed when you need to. The camera’s base ISO setting is probably low and will not be suitable for all lighting conditions. Using a lower ISO means you will often need to use a slower shutter speed. 

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This is one of the key advantages of digital photography. You can choose a low ISO or a high ISO for each image you make. With film cameras, you do not have this option. You are stuck with the base ISO of the film speed until you change the film.

ISO Setting in Film

In terms of film sensitivity, ISO is used as a rating system to tell you how responsive the film is to light. This is the film speed.  The lower the ISO setting (i.e 50), the more time the film needs to be exposed. The faster the ISO film speed, the less light is required to take a picture.

This is the same in digital photography, you just have more flexibility to adjust ISO settings and can do so as often as you like. Using a film camera you must expose the whole roll of film at the same ISO settings. If you make ISO adjustments part way through a film it will throw out the exposure when the film is developed it will not be correct.

What are the ISO Values?

Each camera will vary, but the ISO value can range from ISO 50 to a much higher maximum ISO. Here are the ISO values you’ll discover in many digital cameras: ISO 100, ISO 200, ISO 400, ISO 800, ISO 1600, ISO 3200, and ISO 6400.

Notice how each number is doubled as the ISO values increase. When you double the ISO speed, your exposure value adjusts by double. So, if your native ISO setting is 100 and you change the ISO value to 200, your exposure becomes brighter. 

You can adjust your aperture and shutter speed to compensate for this. In digital photography, cameras usually allow you to manage the ISO settings in one-third of a stop increments. Aperture and shutter speed settings also adjust in one-third increments.

ISO and Noise

Increasing the ISO to a high value affects your exposure. It can help you set a faster shutter speed. But it does have its consequences. Every time you shift from a low ISO value, it creates something called digital noise. This is not the same as film grain.

Digital noise will show up as tiny spots or bright pixels on your photos. They are more noticeable in darker areas of the image and are less noticeable when you use a low ISO.

Digital noise is affected by the size of the pixels in the camera sensor. Larger pixels will result in less digital noise. This is why DSLRs and mirrorless cameras do a fantastic job at higher ISO values compared to compact cameras.

With this in mind, it’s a good idea to maintain a low ISO value and adjust the aperture or shutter speed first. Sometimes, however, lighting conditions are poor and you will have to compromise image noise for brightness. But with most modern digital cameras there is not so much noise as in older cameras.

Luckily, many cameras nowadays do an amazing job of managing sensitivity to light to maintain image quality. You can be more flexible in your exposure triangle settings. You can choose a fast shutter speed when you need to without such a risk of getting noise from your digital sensor in your images.

What is the Best ISO?

When you want to keep a fast shutter speed, in many situations it is not possible to produce an image with low ISO sensitivity. Such situations include those where there is low light and no tripod. Or where the motion is very quick such as in sports photography you will risk motion blur. In this scenario, you’ll want to use a high ISO. A low ISO is not suitable.

Man photographing outside on a sunny day looking at ISO settings in the DSLR camera screen.

On a sunny afternoon however, you won’t have any problems with light. You can use a low ISO. Between a sunny day outside to nighttime photography, you will have to experiment with low ISO and high ISO values. You need to find the right balance between exposure and image noise to find the best ISO. Here is a quick guideline of common ISO values depending on the lighting situation:

  1. Bright, sunny day outside: Use a Lower ISO, 100 or 200 or your base ISO
  2. Cloudy days, indoors, or window light portraits: ISO 400
  3. Indoor photography without flash: ISO 800
  4. Reserved for very low light conditions: A high ISO of 3200 or higher

Suggestions for ISO Settings in Various Scenarios:

  • Dusk: ISO 200 to 400
  • Stars: ISO 800 to 1600
  • Sunsets/Sunrises: ISO 200
  • Evening Parties: ISO 800
  • Stormy Weather: ISO 400

Since you want the sharpest photos possible the ISO is a setting to keep an eye on. Remember that the higher you set the ISO the lower light your camera can handle. At higher ISO settings the sensitivity to light increases. When you want a brighter image and avoid motion blur, you need the camera’s sensitivity to be higher.

Modern cameras are great, but sometimes it is still necessary to use a tripod and a longer shutter speed. This can help you get more depth of field when using ambient light or flash and avoid camera shake. When there is not enough light, the challenges of setting the exposure triangle are greater to capture a correct exposure.

Film ISO vs Digital ISO

If you are using a film camera there is a much better chance that you are already familiar with the ISO number. When you choose your film you select the ISO number. Digital cameras are not so constrained by a roll of film having one set ISO sensitivity. You can change the digital sensors’ ISO sensitivity for proper exposure of every frame.

In film photography, when the ISO is too high, photos tend to appear grainy.  Grain is often mistaken for being the same as noise, but it is not. How ISO affects the look of the film is different from the high ISO effect on digital sensors.

How does ISO affect a digital image? In low light, the higher the ISO, the greater the risk of digital noise than at the lowest ISO setting. With a low ISO number, you see less noise and smaller grain than at high ISO settings in a proper exposure.

What is Native ISO?

Native ISO, is a crucial camera setting that will help you in producing the highest image quality. This is the baseline setting your camera is automatically set to for the best image quality and detail. 

At this setting, your camera’s sensitivity is optimized. This particular ISO is best whether you are using a full-frame camera or a crop sensor. Most cameras have this setting as the lowest available. Understanding ISO helps you capture light and maintain the best image quality.

What is Auto ISO?

Auto ISO allows photographers to manage their noise balance while taking photos. Turning on Auto ISO is never a good idea if you’re prioritizing Shutter Speed or Aperture mode. Allowing the camera to increase or decrease the ISO based on the current exposure settings take more creative control from you. 

Getting a good grasp on understanding ISO and how it functions will help you make better choices about setting up your camera. This, in turn, will produce good quality photos. This is why it is important to control your ISO manually.

How to Adjust the ISO Settings?

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There are many ways to adjust the ISO depending on the type of camera you have. The following are the most common ways:

  • Get your camera out of Auto Mode. Including Auto ISO. Manually control the exposure triangle for the best results.
  • You can change the ISO value from the menu.
  • On more advanced or professional cameras, there is usually a dedicated ISO button. Press down on the ISO button while turning on the dial to change the ISO values. If you don’t see an ISO button, you may be able to customize it. Check your user manual for more information. 
  • Some cameras will also feature wheels where you can quickly change the ISO.

ISO Camera Setting Tips

  1. Do you hate that flashy look of photos indoors? Turn the flash off, lower your aperture and raise your ISO. You shouldn’t need a flash.
  2. Want to tell a story with your photo? Open your aperture all the way (lots of people refer to this as wide open) and blur out some elements of the photo. This is a shallow depth of field.
  3. Photographing sports? Set shutter speed faster and your subject suddenly becomes sharp! Use a higher ISO to help you maintain a fast shutter speed.
  4. It helps to take three or four pictures, each with different settings, so you can get a feel for how each setting will change your photo.

Debunking the ISO Myths

There are many misconceptions about ISO and how it works. Let’s take a quick look at the most common myths:

  1. ISO is related to exposure.
    Interestingly, ISO is not part of exposure. Whereas aperture and shutter speed physically capture more light into the camera sensor, ISO doesn’t do that. Instead, ISO brightens or darkens a photo based on the captured image. This is why many photographers don’t consider ISO part of the exposure triangle.
  2. ISO is the sensor sensitivity.
    This is probably the most common myth about ISO, and it’s actually false. ISO doesn’t reduce or increase the amount of sensitivity in your camera sensor. In fact, your digital camera only has a single sensitivity. ISO simply brightens your photo based on the current exposure. It maps how bright or dark the photo will be based on the ISO values.
man taking photo of sunset mountains with ISO 200.

Conclusion

Learning to control ISO helps to get your images correctly exposed. It helps us control the other two parameters of the exposure (aperture and shutter speed) which all work together to create a proper exposure. 

  • The higher the ISO, the more responsive the film or digital sensor is to light.
  • ISO speed affects aperture and shutter speed choices.
  • The higher the ISO, the more grainy or noisy pictures may appear.

Knowing how these parameters work together will help you grow as a photographer. This understanding helps develop your creative vision. Especially when you are photographing in various light conditions. With enough practice, you’ll be turning the dials and adjusting your ISO settings without thinking twice.

We hope this information was useful and that you’re ready to start controlling your ISO! Let us know your thoughts, comments, and experiences below about ISO.

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  1. This lesson sums it up just fine so that I understood it exactly with a few precise words- rather than a lot of long paragraphs. I will play around in your site more. This was my first spot on the website.

    Thanks for the information and for taking your time to post it.

    Margaret

    1. Your welcome. I hope you enjoy the rest of the lessons. If there’s anything you think we’re missing let us know. We’re always looking for new lesson material.

  2. Enjoyed the review on ISO. I now use a digital camera most of the time. If I set it to “No Flash” Does this force the camera to automatically increase the exposure time in a low light setting? I like to use a tripod and often do not want the glare of a flash.

    1. If your camera is set to automatic then it will automatically update the exposure. If it’s set to manual you will have to compensate for not having a flash. It’s great that you use a tripod in such cases and I agree that a flash can ruin any great composition.

  3. Hello,

    From the lesson I have understood what ISO is, but i still have not figured as to when one could use higher ISO’s or lower ISO’s. Could you give an example. In the sense, if you are capturing a bright object, is the ISO to be set to at a relatively high number and vice versa?

    Awaiting your response!

    Thanks in advance,

    Nutts

    1. Because lower ISO provides higher quality photography it’s recommended that you use low ISO sensitivity as often as possible. High sensitivity ISO, around 1600, results in grainy photography. High Sensitivity is typically used when you want to capture very quick motion such as in Sports Photography, or when you cannot make the shutter speed any slower or open the aperture any larger in low lighting conditions.

  4. Thanks a lot, it is what we say less words more knowledge. i am beginner in photography and i am gaining a lot of information from this site. ENJOYING PHOTOGRAPHY WITH MY NOKIA N86 8MP Camera. KEEP GONING DUDE

  5. Thank you for this wonderful lesson very straight forward and easy to understand! i’m a beginner and I’m trying to learn everything i can! congratulations to the admins for the good work!

    David

  6. NOW I understand why I’m getting grainy photos in certain low-light conditions. I need to use the ISO setting! A simple discover that will make a huge difference in my low-light photos.

  7. Hi,
    Thanks a lot for understanding on ISO..I’m new to photography and want to learn it badly, I first thought ISO was just to improve the light factor? but never heard the term aperture before? not sure what that is, I have a Canon Rebel XT.. I was planning on buying Nikon D90(felt really comfortable with it)not sure to ask but do you favour Canon and why ?
    Kindly let me know.

  8. Oh! at last i got the answer,(what is ISO?)…
    I m a beginner and very confused about ISO & Aperture.Now i get it.Thanks a lot……I also want to learn more from u…I know u help me to be a professional…

  9. WOW. It is nice. Straight & to point. Now I have a question, somehow I think maybe it has to do with ISO but not sure. I have a basic Nikon CoolPix S570 with wide 5x zoom & no clue what that means either lol. BUT, I want to know how to blur the background in a photograph. Maybe what the wide 5x zoom means Thanks in advance!
    Tammy

    1. What you’re referring too is the depth of field. To get the effect you’re talking about you need a wide open Aperture. And a long focal length (Zoomed all the way in). You’ll have to use manual mode to change the settings, even then your camera may not have a long enough focal length or an open enough aperture to make the effect you’re looking for.

  10. Your ISO really help me lot to make my photography better. Thank once again for the details you provided about the difference between Film ISO and Digital ISO.

  11. I love to do photography but i am little slow in english thats why sometimes I don’t understand but this time it was very easy and quick to learn photography. I tried this at my own I got wonderful pictures
    Thanks to this website who teaches a free photography course very easy and quick
    Aditya

  12. Thanks,now I understand better about digital ISO.I use to take my pictures, the Nikon D50 and Nikon D80.Thanks again.

  13. I have had my Nikon D80 for 2 years and don’t know how to use it properly. I have now learned about ISO. Will practice tomorrow at day light. Any tip on how to get great pictures with the Nikon D80 will be appreciated. I love photography. Thanks to all who reply.

  14. um…
    I’m 14 and I’m still a bit of an amateur i have a Nikon D70, my dad is also a pro photographer but he doesn’t have time 2 give me photography lessons so I’m learning the hard way. I do a lot of action photography, any tips will help, also if you would like to see some of my photos and point out my flaws its on the following url:http://www.flickr.com/photos/steenkamp/ thanx 4 all u ppl who do give some tips

  15. The lecture was great but I wanted to know if zooming has any thing to do with ISO because whenever I zoom the picture appears darker.

    1. ISO isn’t effected by zooming but the aperture is. The more you zoom in or the longer the focal length: the less the aperture can open and that’s why you are getting darker pictures when you zoom in. After you zoom you have to re-evaluate your exposure.

  16. I have a cannon 5d and am still learning. My photos have been selling well but I am concerned that they don’t have that real sharp clear look to them. Can you give me any tips. Also if the iso should be lower and it isn’t a really bright room would I just have to change other settings to let more light in instead of going higher in iso. The last practice I did was in a bedroom and the photos were very noisy.
    This is the best site I have come across by the way. IT’s fantastic for us beginners !!

  17. Just found this site…I’m a beginner myself and I really want to learn Photography and hopefully get a degree. I actually learned a lot with not so much of reading long paragraphs. I like how its straight to the point and understandable at the same time.

  18. God bless you all for all the information on this site, I’m just about to buy my first dslr and I’ve always loved photography and wanted to be a pro. I’m excited and eager to learn, I’ll update you as I get along.

    1. Lowest is always best, but it depends on if you can use a tripod or if your subject is in motion. If they are moving and there isn’t much light you’ll have to increase the ISO. It’s kind of a last resort setting.

  19. This is great! I´ve heard all this concepts before but had no clue what they meant. I love it how you “tranlate” them into examples. Now I know what to do with ISO! It´s not chinese anymore. This is exactly the type of site I was looking for to learn about photography in simple words. Thanks again!

  20. love the site! have a question on ISO: when I’m on manual mode I currently have ISO on auto. But having read the above I understand that the lower the ISO the better. so if I’m setting aperture and shutter speed I’m assuming that the ISO will automatically adjust to get the best exposure? which may mean the ISO goes higher than it needs. So it would be better to set this manually too?
    also when you’re in fully manual, which do you set first? aperture or shutter speed and ISO? I know it’ll differ if the subject is moving or not – if moving you want to reduce shutter speed. and then for static pictures would you always set aperture first to control the depth of field?
    so far I’ve been trying to get my head around the technical side of things, but when it actually comes to taking a photo on manual mode I feel completely at a loss!!! Are there any good starting points? I liked the guidelines for aperture dependent on how much natural light there is but not sure where you would start on shutter speed….
    Looking forward to your response
    Thanks

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