Camera ISO Settings Explained – Sensitivity to Light

Welcome to my post ‘ Camera ISO Settings Explained ‘. The term ISO in photography has been around since the early days of film. It stands for Industry Standards Organization. This is the governing body that sets the standards for sensitivity to light for photographic mediums such as film or a digital sensor. ISO also sets standards for hundreds of other products.

Sensitivity to Light

When we depress the camera button to take a photograph, light travels through the lens and is projected onto an image sensor that is placed inside the camera body. By the way, film used be where the image sensor is in modern digital cameras. The image sensor can be adjusted so it would react differently to light. It can be set to react fast or slow to the light falling onto its surface.

If you are shooting outdoors in a sunshine, you may want to set it react slow. Because there is an abundance of light available. You may run into the risk of making your photograph overly bright if you set it to react fast where more of light available. These settings are excellent choice for sharp images.

Indoor photography or where there’s lack of good light source, you may want to set the sensitivity to fast. These setting gives you a good starting point. Keep in mind higher settings can produce more grain and could rob your photograph from the finer details you may want in your photo.

ISO Settings

The ISO is also referred to as the film speed. Of course the film is almost obsolete, so we will be talking about the image sensor. The speed is expressed as numbers. Typically, these numbers look like,50, 100, 200, 400, 800, 1600 and so forth. Notice how they double in size. Every time the ISO is increased or doubled, the camera needs half as much light to produce the image. My camera goes all the way up to 12800.

Smaller numbers reflect that the image sensor will react slow to light. Numbers in the range of 100 – 400 are useful for sunny beach days or sunny snowy days. Using these setting will give a desired exposure in bright situations.

Settings in higher ranges such as 400-800 are useful for indoors where standard household lighting is available. A flash unit may be required to fill in that extra needed light. As I have mentioned earlier, when we start going higher, the grain or noise in your photo could become a problem. Modern digital cameras are becoming more technically advanced. Engineers are constantly working to reduce noise yet still use a higher ISO.

Auto ISO

Digital cameras can be set to auto ISO. This means the camera will automatically select the ISO based on the lighting conditions. Most point and shoot cameras, and cameras in you mobile phone are all automatic. The problem with auto ISO is that the camera raises the ISO if there’s lack of light, therefore producing images that are noisy. This is where learning a fully manual camera pays off. This allows you to control every aspect of the shot.

How to Select Best ISO settings

Photograph is a combination of ISO, aperture, and shutter speed. All three are dependent on each other. As guideline, use lower speeds in bright situations, higher speeds in low light or dim situations. In order to select the best ISO settings, you must also select the best aperture, and best shutter speed. This is called the Exposure Triangle. I will be writing a separate post on that topic. Also, learning by doing is the best approach. It is much cheaper nowadays to practice on a digital SLR camera, than it was on old film cameras.

I hope you have gained some insight on what is iso and how it is applied.  Remember to read my other posts on “Lens Aperture Explained,” and  “Shutter Speed Explained.”   Please feel free to leave questions or comments below


Pardeap Sambi

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  1. Hi Pardeap,

    I had no idea what ISO meant until reading your article. To be honest, I am not a photographer so I also wouldn’t know to look into this at all. However, I do like taking pictures and I think the ones with natural light are the best. My question is whether or not you can adjust ISO on modern cameras? If so, are the numbers you listed standard or are they changed by companies. For example, if Fuji came out with a camera would their ISO numbers be 75, 125, etc.?

    1. Author

      ISO numbers are standard across all cameras.  You can adjust ISO on DSLR cameras.  On fixed lens cameras, it may or may not be possible. That depends on the make and model. 

       Other cameras such as cell phones, all the setting are automatic for the most part. 

  2. I have been a photographer for over 30 years, and ISO was an everyday word back in the day.  I had two cameras I used for shooting because I had one with 100 ISO in it, and one with 400 ISO in it.  Each gave a completely different photograph.  I took wedding photography, and I would take pictures back and forth with the two cameras.  Think about how things have changed since then.  It’s so much easier now, but I can’t help but think far less artistic.

  3. You know I have seen ISO on DSLR’s for years and never fully really understood it.  I knew it has something to do with lighting, though.  

    What would you recommend that the typical DSLR ISO setting has as a minimum or maximum, though?  Also, do cameras with an auto ISO typically cost more or is that a standard feature?

    Sorry for the newbie question.  I am going to be taking some pictures shortly of animals and people and want to make sure I do it correctly.

    1. Author

      Most modern SLR’s ISO ranges from 100 to 12800. If you’re shooting animals outdoors with natural sunlight, then iso settings of 100 to 200 would give you nice results.

      All modern DSLR cameras have an auto mode.  This mode does all the work for you. It selects all the necessary setting including iso based on the lighting conditions.

      And don’t be sorry for any newbie questions. That’s the aim of my site is to educate people about lenses and camera bodies , and photography in general.

       Get that camera out and start taking photos!

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