The Third Factor in Exposure Triangle - The ISO

As I mentioned about the last blog, the combination of the three factors that determines an camera exposure were aperture, shutter speed, and ISO. I planned to blog all three factors on one blog but I thought it would be overwhelming, so I broke them into two blogs to make it easier to understand. On this blog, I'd like to add some details of the last leg of the exposure triangle, which called ISO.

 

As the aperture and shutter speed, the ISO also controls an amount of light get into a camera' sensory. Before getting to know how ISO effects on a photograph, let's go over its definition, and see what that is about. According to Nasim Mansurov in his photography guide for beginners, he describes that:

ISO – the level of sensitivity of your camera to available light. It is typically measured in numbers, a lower number representing lower sensitivity to available light, while higher numbers mean more sensitivity. More sensitivity comes at the cost though, as the ISO increases, so does the grain/noise in the images. Examples of ISO: 100, 200, 400, 800, 1600.

I always keep in mind that higher ISO means more light coming into the camera sensor and lower ISO means less light coming into the camera sensor (Yuen Mun) I'd like to make it simply by showing a few photographs that I took at different ISO levels.

I took this photo when I was on the top of the mountain. It was sunny so I chose ISO 100 because there was full of light.

I took this picture with ISO 200 because there was in the morning and it was cloudy.

I took this photo in the early evening and there was not too much light so I chose ISO 400.

It's a gift from my friend. I took this photo in my room with light source from the lamp. I set ISO at 800.

From these examples, I'd like to say that ISO levels depend on what we want take a photo of. In different cases, the light comes from different sources so we need to determine an amount of light to set up the ISO levels. It's very simple but there is more about it. Sometimes, when taking photos at the night time, ISO settings are usually high because the light is very limited, and resulting that a photo would be noise. In other words, a photo doesn't look crisp and clean, it has more grain. 

 

In short, the exposure of a photograph is controlled by only three factors: aperture, shutter speed, and ISO. By understanding the three factor photographers can easily adjust settings in every situation and create an art of combining all three. In an article, Yuen Mun said: 

For best results, photographers should decide which combination of settings to use. Knowing the relationship between the settings allows photographers to quickly adjust settings while keeping the exposure constant.

I'd like to share more details of combining all three factors in different situations. If you are taking a landscape photo, you should set small aperture to increase the depth-of-field. When taking landscape, we usually have a plenty of light, the ISO should be low about 100 or 200. If you are taking a portrait photo, you don't need the depth-of-field, so you should set bigger aperture, and the ISO depends on the light the time you take a photo. If you are taking a macro photo, you need to set very big aperture because you need to focus an object in close distance, shutter speed should be fast because while the aperture opens like this, a plenty of light comes into the sensor, and the ISO should be around 100 or 200 for a clean photo. They are cases that I want to share. Now, I think you should take your camera and try to set the three factors depending on what you want to take. Then, you will see how it works.

Work Cited:

Mansurov, Nasim. "Understanding ISO, Shutter Speed and Aperture – A Beginner’s Guide." www.mansurovs.com. Mansurovs Photography, 12 Jan 2010. Web. 19 Sept 2012.

 

Mun, Yuen. "Relationship Between Camera ISO, Aperture and Shutter Speed." www.suite101.com. Photography at Suite101, 10 Apr 2010. Web. 19 Sept 2012.