What Is The ISO On A Camera – Recognize the Need of Light

Nikon d7100

The ISO is important in your camera, but what is the ISO on a camera and for what purpose? This thing is one of the other two important channel in the camera (Aperture and Shutter speed) 

The use and function of the ISO on your camera is simply to add a light or brightens in the image or a subject that you want to take the picture. It helps to increase the sensitivity to light, that function in the image sensor.

Many beginners are looking for the answers of what is the ISO on a camera. You will go to ‘M’ manual mode. 

To use the ISO it allows you to be like a photo director, you will decide to the result for your image it is like an application of adding or decreasing the light.

To do by pressing a button and dialed controls on the camera to lower or higher the ISO sensitivity. Let’s start an exercises 🙂

For example, set on a camera your shutter speed then select also your aperture then lastly look your ISO.

  • Shutter speed : 1/250s
  • Aperture (opening) : f/5.6
  • ISO : 100

Now, my question to you. What do you think about this settings? Is it for daytime shooting or for nighttime shooting? The answer is daytime shooting.

Notice that the aperture is f/5.6 and if you look on the chart of aperture of f/5.6 it is semi wide open hole.

Relationship of Aperture, Shutter speed, ISO

As you fix the aperture you have to adjust the shutter speed and the ISO if your image under or over exposure. While the opening(Aperture) is bigger at daylight make your shutter speed faster or increase it by one step or two forward, if your image is over exposed example from 1/250s to 1/500s and so on.


That is the important for beginners to learn how to use of the ISO. In three letters I. S. O. Will make your image bright.


Charge Couple Device
A CCD or Charge Couple Device (The Image Sensor)

The Acronym of ISO

It stands for International Standardization Organizations, but the word Organization in the digital camera do not directly turn into as organization due to various companies and technology produce products. Early days of the camera or manual camera is called ASA and accepted as the ISO.

The Invention

The above picture is the Charge–coupled Device or (CCD) was invented 1969 by two guys below image in the United States by George E. Smith and Willard Boyle.

Two Men Invented the CCD
The Inventors of CCD, the sensor image now is use also in digital camera.

A device that allows the movement of electrical charge, and in the device within manipulate in that area, like for example a conversion into a digital value. And this is attained by shifting the signal between the stage within the device to one at a time.

What are the ISO

You have in your DSLR or digital camera the ISO parameters. Note that as you increase the ISO on your camera the grain start to appear or it is called the “Noise”. If you go directly to see the ISO parameters you have:

  • ISO 100……… Your low ISO or this is your base.
  • ISO 125
  • ISO 160
  • ISO 200
  • ISO 250
  • ISO 320
  • ISO 400
  • ISO 500
  • ISO 640
  • ISO 800
  • ISO 1000
  • ISO 1250
  • ISO 1600
  • ISO 2000
  • ISO 2500
  • ISO 3200
  • ISO 4000…….. In here you will find the noise in the image specially when you night shooting.
  • ISO 5000
  • ISO 6400…… High ISO
  • Hi 0.3
  • Hi 0.7
  • Hi 0.1
  • Hi 0.2……….. Your very High ISO.

Above parameters, I checked my own DSLR camera. To understand while you are increasing the ISO for example ISO 100 and you go to ISO 200 means you double the light of image.

Exposure Triangle
Be familiar with the Exposure, the Aperture priority , the Shutter speed speed and the ISO speed.

Definition of Grain in the Image – the noise

For instance an indoor situation you can increase start from 1600 ISO to 3200 ISO. The grain or noise will appear more than that parameters or over 3200 ISO. As you add or increase the ISO the brighter will increase in the image become more and more light. Remember that the ISO on your camera the more you increase parameters the sensitivity to light increases.

The Grain or granularity can be seen after the photo was taken, it is the random optical texture of process in photography film due to the presence of tiny particles as you enlarge the finish image. Mostly photographer called this as a noise, they don’t like this definitely. They are very careful with called noise.

Proper using the ISO

Once you learn the ISO, you will maintain at low settings of the ISO parameters in any photos that you are going to take a shot.

Definitely not good image to see that noise appearing there. And when I am trying to make a shoot l can start the standard which is 100 ISO. Then adjust it after one to another until you found limit for subject to make photo.

For beginners step that is normal but in the future you can learn a lot, seems you feel it the light when it needs. It follows of course the settings of the aperture and the Shutter speed.

The ISO sometimes do not work, when?

You notice not all the time the ISO is working. Your shutter button will not sometimes work specially when you start shooting at nighttime .

The basic solution for this and if you are experiencing a problem, don’t worry. There is no problem with the camera. The answer for this is to increase your ISO, try to adjust it so that your shutter will work. (the camera has a warning signal blinking on view finder screen or in LCD). Remind you to change it.

You have to full open your lens. Bring your Aperture to f/1.4 or f/1.8 set up and then increase your ISO to1600 up to ISO 3200 and use your flash for better bright shot image.

As you increase your ISO, start to increase also your shutter speed from 1/125s to 1/250s. I have tried the shots playing volleyball in the night, it’s amazing shot. The players freeze in the air while defending ball in the net center.

Where can I find the ISO on the camera?

You will find the ISO easy and written as it is on your DSLR camera. First step go to the wheel to rotate or dial mode. If it is in Auto change it to:

  • Manual mode
  • Aperture priority
  • Shutter priority

In Digital camera with mirror less – change to manual from auto mode and then look for menu button and press that menu. Find the ISO by scroll down using arrow press button then click and choose the number of ISO you want.

The Digital Single-lens reflex camera – After you select to manual mode you can start to look the button and written also ISO, press that button then start to increase or decrease the number. Here is the short video where to look for the ISO.

1. Press and hold the button on your left thumb.

2. Dial using your right thumb to increase and decrease the ISO. Dial going to the right to increase and going to the left to decrease.


If you have any questions about the ISO please leave me below and I will be more than happy to help you out. Thanks

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