Effects of ISO Settings on a Photo’s Exposure.

 
The third elemental key to understanding how to take a really great shot is a knowledge of your camera’s International Standards Organization, commonly known as ISO.   The first two elements we have already had a look at, and these are the shutter speed and the aperture.  When you use the three elements together it is known as ‘the exposure triangle.’

To understand ISO we must take a little trip back in time to before the digital era.  With a traditional camera and film the ISO value referred to how sensitive the film was to light.   Nowadays, with digital cameras the ISO refers to how sensitive the image sensor within your camera is to light.

 

 
 

A camera’s ISO value ranges from 25- 2300 and this is set according to international standards, which means that whatever the make or type of your camera, the setting ISO300 will be the same on all, for example.    The values, the same as those for shutter speed and aperture, increase in doubles, so that you double the exposure, or halve it, with the ISO adjustment setting.

The ISO settings affect the grain, which is a kind of speckling effect, in a shot.  The lower the value of sensitivity (ISO rating), then the lower the sensitivity of the image sensor and hence the finer the grains in the scenes captured.

In trying to capture a scene without much light,  it is appropriate to set a higher ISO rating whist in brighter scenes a lower ISO rating is required.  You also need to note that the higher the choice of your ISO ratings, the noisier the shots will get.

 

 
 

When you make manual adjustment to the ISO settings there is a correlating effect to the aperture and the shutter speed, which will require equal adjustments to these settings for the scene to be captured with the ideal exposure.

For example, increasing the ISO from 100 to a 400 setting will allow you to capture scenes at higher shutter speed or with smaller aperture.

 

 
 
 

Factors to consider when adjusting the ISO setting.

 

 
If you are trying to capture a still shot with a little grain and you are using a tripod in good light then you would select a low ISO setting.

On the other hand, if the scene you would like to capture is not well lit, you don’t have a tripod or stabilizer, or  there is motion, then you would select a higher ISO.

 

Nowadays, people only look at the ISO numbers, as a way to predict how well the camera will perform in low light conditions, like night photography. The bigger the number, the better success you will have in dark places. Digital cameras are getting better and better at night photography, but they still aren’t perfect.

I’m a pilot, and sometimes I’m flying at night, and wishing I could see what was on the ground. I’m still waiting for an affordable camera with an LCD screen, so I can aim it outside my airplane cockpit and be able to see low-light details on whatever I’m flying over. I’m writing this paragraph in October 2015, and today there are cameras on the market that can do a good job with night photography, but they are very expensive, like $20,000 per camera, which is sadly for me, more than I want to spend. Maybe in a few years.

My own canon eos 7d mark 2 camera, isn’t great for night photography. Here’s a picture of the moon, that I snapped. It was from Berlin, but I had a beer earlier that afternoon, and was sleeping during a lunar eclipse and blood moon. Those photos of a red moon were all over the the internet, but not taken by me. I was asleep. When I finally woke up, and realized I missed the eclipse, I took this moon photo, for fun. Quite a lowsy photo.. Then below, you can see how photoshop can make it show a little more detail, but it becomes very grainy.