What is ISO in Digital Cameras?...and When to Change an ISO Setting
This tutorial answers the question, what is ISO, and how to use the ISO setting function in your digital camera.(ISO is an abbreviation for the International Standards Organization. It is an organization that sets the standard ratings for numerous products and services.)
In digital photography, the ISO rating or number is an indicator of how sensitive a camera's image sensor is to light at a specific setting. Changing your camera's ISO setting will amplify or decrease the image sensors' ability to read and gather light during an exposure.
When your camera is set to a higher numbered ISO setting such as ISO 800, less light is needed to obtain a correct exposure than if the camera is set to ISO 100 for the same shot. That is, assuming other factors such as the camera lens aperture setting, and the shutter speed setting remains the same.
Some of the most common ISO settings/ISO numbers are listed below.
In digital photography, the ISO rating or number is an indicator of how sensitive a camera's image sensor is to light at a specific setting. Changing your camera's ISO setting will amplify or decrease the image sensors' ability to read and gather light during an exposure.
When your camera is set to a higher numbered ISO setting such as ISO 800, less light is needed to obtain a correct exposure than if the camera is set to ISO 100 for the same shot. That is, assuming other factors such as the camera lens aperture setting, and the shutter speed setting remains the same.
Some of the most common ISO settings/ISO numbers are listed below.
64 |
100 |
200 |
400 |
800 |
1600 |
3200 |
6400 |
12800 |
Each higher ISO number listed above makes the camera's image sensor twice as sensitive to light as the one before it. For instance, setting your camera's ISO number to ISO 400 will make the image sensor twice as sensitive to light than if it were set to ISO 200.
The Exposure Triangle: The ISO setting, camera shutter speed, and lens aperture setting are all part of what is known in photography as the "Exposure Triangle". These three things work together to produce a properly exposed images. Check the Camera Lens Aperture and the Camera Shutter articles to learn more about their functions.
A basic compact camera like the Canon Powershot ELPH 190IS has ISO settings that range from ISO 100 to ISO 6400. The Nikon D3500 Digital Slr camera has settings from ISO 100 to ISO 25600.
Automatic and Manual ISO Settings: When you use your camera in the fully automatic mode, the ISO number may be automatically set for you. The ISO number that the camera chooses will depend upon the amount of available light as well as the most reasonable shutter speed and aperture setting that will produce a well exposed image.
If are using a camera that can be set to manual, or a semi automatic mode, you will be able to choose the ISO number yourself.
Lower ISO numbers are better:. While it is a great thing to be able to increase your camera's ISO rating in order to get the shot you want, there is a down side to doing it. The down side is called "digital camera noise"
The higher your ISO setting, the more noise you will see in your picture. Noise is tiny dots or specks in the image that are generated when the image sensors' sensitivity is amplified in order to read more light.
Picture #1 taken at ISO 1600 shows excessive "noise" (click image to enlarge)
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Picture #2 taken at ISO 100 shows less visible noise. (click image to enlarge)
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Picture #1 was taken with a setting of ISO 1600. Picture #2 was taken with a setting of ISO 100. You can see that picture #1 is more grainy or speckled than picture #2. (Click either picture to enlarge. That way you will be able see more clearly what the noise would look like on an enlarged print) The difference between these two images is the amount of "noise" that is visible.
There is always a little noise in a photographic image, but the noise might not be visible unless the image is greatly enlarged or the ISO is set to a pretty high number. Also, as you can see, digital camera noise will be more visible in darker areas of the image.
The amount of noise in an image will also vary depending on the type of camera being used and the size of the camera's image sensor. Digital Single Lens Reflex cameras, because of their larger sensors and pixel sizes, will exhibit less noise than basic Compact Digital Cameras at higher ISO settings.
In any case, getting a nicely exposed shot with some noise in the picture is better than no picture at all.
When should the ISO setting be changed? A simple example would be when you are photographing a dimly lit scene or setting and it is not possible or logical to use the camera flash. Lets assume you cannot get a properly exposed picture, (the picture is too dark) and the camera is set on ISO 100. No problem!
Try changing to a higher ISO setting like ISO 400, ISO 800, or which ever ISO setting will allow you to get that properly exposed picture. As was previously mentioned, using higher ISO setting numbers makes the image sensor more sensitive to light. Therefore, less light will be needed to produce a correctly exposed image.
The next example applies if you have a camera that allows you to manually change your camera lens aperture and shutter speed settings. If you are not familiar with how they work together (along with the ISO setting) to make properly exposed images, please read Camera Exposure Basics.
Lets say you are trying to shoot a fast moving subject and your camera is set on ISO 100. Your camera's exposure metering system indicates that a lens aperture setting of F3.5 along with a shutter speed of 1/60 will produce a correctly exposed image.
However, the shutter speed 1/60 second might not be fast enough to "freeze the action. (moving subjects might be blurred in an image when you are using slower shutter speeds).
The best way to solve the problem is to start by changing your camera setting from ISO 100 to ISO 200. That will decrease the amount of light the camera image sensor will need for a good exposure. You will then be able to increase your shutter speed from 1/60 second to 1/125 second as you attempt to get a properly exposed image.
If that shutter speed isn't fast enough, change from ISO 200 to ISO 400. Then increase the shutter speed to 1/250 second. (let's assume that the shutter speed of 1/250 is fast enough to "freeze" the action). You will then have a nicely exposed image without any blur in it.
Keep in mind that each of the adjustments made to the ISO setting and the shutter speeds in the example above are equal steps. That way, the correct exposure will be maintained.
There also may be times that you might have to change the ISO setting if you want to use a specific lens aperture opening instead of adjusting the shutter speed. The same principle that was just used with the ISO and shutter speed combination can be used the same way with the lens aperture and ISO settings.
In any case, always remember that adjusting the ISO setting may save the day when the shutter speed and aperture settings are not producing the exposure you may want for your image.
So now, the question what is ISO?, has been answered and hopefully you will be able to use this information when making decisions about exposure settings for you images.