"I Hate My Camera!" - Understanding ISO

ISO 100, f/2.8, 1/50 sec, 25mm

ISO is not an acronym.  It is pronounced “I-sow” - one word, not I.S.O. I'll write more about this for the geeky people at the end of this blog because in reality, this aspect of ISO belongs on Jeopardy.

ISO is one third of the trinity of photography. The other two are aperture and shutter. If you have not read the blog on each of these other two aspects of the photographic trinity you can follow these hyperlinks: Aperture Shutter 

ISO relates to the speed of your camera's sensor.  

WHAT in the world does that MEAN? I’m glad you asked.  

Back in the good old days of photography, when we used film, the ASA number (not ISO) referred to the speed of the film. A low number like ASA 100 meant that the film was slow and need a lot of light to burn an image on the film. A high number like ASA 800 meant that the film was fast and needed less light to burn an image on the film.

The ISO number does exactly the same thing. An ISO number of 100 means that the sensor is functioning at a slow speed and needs a lot of light to capture an image. An ISO number of 1600 means that the sensor is functioning at high speed and needs less light to capture an image.

You with me? Take a deep breath and say to yourself ISO, ISO, ISO.

Here’s the hard part...setting the ISO number on your camera. Grab your camera and pick up your manual before continuing…I’m waiting..

LET THE WORKSHOP BEGIN!

1. Look up “ISO” in your table of contents or index.
2. Find out how to change the ISO number on your camera.  
3. Practice changing the ISO number. Don’t worry about what this is doing to your camera. You won’t break it. When you feel comfortable changing your ISO number you might want to set it to ISO 400. This is a good general purpose ISO setting.

I know that your hands are shaking and sweat is beading on your forehead. You have just taken a major step in knowing your camera. Learning your camera is a process of trial and error (with intermittent desires to throw it against the wall, or take it back to the camera store).

Now that you know how to set your camera’s ISO (or soon will), let’s talk about why understanding ISO is important.

• It’s all about light: ISO 100 means that your shutter will need to stay open longer than ISO 1600 for a proper exposure.
• It’s all about shutter speed: ISO 100 will slow down your shutter and make objects look like they’re moving. ISO 1600 will speed up your shutter speed to help stop action.
• Here are four examples of how ISO can aid your photography.
• ISO 100 is good for landscape photography on a sunny day.
• ISO 100 is good, when used with a tripod, for making water silky smooth.
• ISO 1600 is good for indoor pictures without a flash when there’s decent light.
• ISO 1600 is good for action photography if your goal is to stop the action.  

So...let me completely confuse you with the following chart. I have my camera out and I’m pointing it at a mug on our coffee table. I have my aperture set at f/2.8. 

Here is the effect ISO has on the shutter speed:

ISO Setting Aperture Shutter

ISO 100 f/2.8 1/10 second

ISO 400 f/2.8 1/40 second

ISO 800 f/2.8 1/80 second

ISO 1600 f/2.8 1/160 second

When hand holding a camera shutter speed is EXTREMELY important. When your camera is properly focused, the faster the shutter speed the sharper your picture. In my opinion a couple of nice shutter speeds are 1/125 and 1/250 of a second. 

Here is the main drawback of high ISO numbers: The picture will have more “noise” or “grain” in it. In other words, it won’t look as smooth as lower ISO numbers and can become a problem when you enlarge a picture for grandma. This is especially true in point-and-shoot cameras because they have a tiny sensor which will exaggerate noise.

Here’s your project: Set your camera to aperture priority with an f-stop of f/10 and take two pictures of the same object. Take one picture at your camera’s lowest ISO number and the other at the highest. Upload them to your computer and compare the pictures. Then have fun experimenting with different ISO settings. You might even take a field trip with the purpose of switching ISO settings. You will note in the following pics the amount of grain in the high ISO photo compared to the low ISO pic, especially if you enlarge the pictures.

ISO 100, f/10, 5 sec.

ISO 16000, f/10, 1/40 sec.

OKAY GEEKS, back to where I started this blog. The ISO standard is set by the International Organization for Standardization. Here is their explanation of the word ISO taken from their website:

“Because 'International Organization for Standardization' would have different acronyms in different languages (IOS in English, OIN in French for Organisation internationale de normalisation), our founders decided to give it the short form ISO. ISO is derived from the Greek isos, meaning equal. Whatever the country, whatever the language, the short form of our name is always ISO.”

Enough said.

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(Click on picture to enlarge.)

Text and Photographs ©Copyright 2012-14 Douglas P. Brauner.  ARR