Skip to content

ISO

What is ISO?

It stands for International Standard Organization. Well, you don’t have to actually remember it. In photography, ISO is a gate that controls the amount of light gets into the camera. ISO means the camera sensor’s sensitivity towards light. So, when the ISO is lower, the sensor has less sensitivity towards light. And at higher ISO, the sensor has higher sensitivity towards light.

iso scale

With the same shutter speed and aperture settings, an image appears darker at lower ISO compared to an image at higher ISO.

iso example

Therefore, more light is needed for good exposure at low ISO and less light is needed for good exposure at high ISO. So, you may use fast shutter speed or small aperture at higher ISO. Using fast shutter is encouraged if you are shooting handheld as to avoid blurred image.

ISO example 2

ISO performance

ISO performance is related to shooting at low light condition, where you are forced to use high ISO so you could use fast shutter speed to avoid image blur. Using a high ISO can results in image noise. Image noise is random grains that appears on the image, which could reduce the image quality.

image noise ISO

However, the level of image noise is affected by the type of camera. Some type of cameras has better ISO performance than the others, means that these cameras produce less noise at high ISO.  The reason behind this is particularly because of the sensor’s size. A full frame camera has better ISO performance than a crop sensor camera. This is because more pixels are packed into a smaller sensor thus creating image noise.

Nevertheless, most developers are putting in a lot of effort to tackle the ISO performance in their models, such as introducing built-in noise reduction. To know how your camera performs at high ISO, you may search  -“your camera model” ISO performance – hehe

Progression of ISO

As shutter speed and aperture have their own progression, so does the ISO. So, the question is, you get a good shot at 1/5 s at ISO 100 but the image is blur. Then, you intend to increase the ISO to 200. Now, what is your shutter speed going to be?

ISO table

Going from ISO 100 to 200 means the amount of light is increased by 1 stop, so the shutter speed must be reduced by 1 stop. Therefore, the new shutter speed will be 1/10 s. There is a trick to remember this so complicated increasing and reducing f-stop. So here is the trick. The number of times you should turn your ISO dial is the same as shutter speed dial and in the same direction (same for aperture). So, if you turn the ISO dial 3 times to the right, you have to turn the shutter speed dial 3 times to the right too.

There is also another way. Since going from ISO 100 to 200 is times 2, so shutter speed should be divided by 2.  So for 1/5 s, you get 1/10 s. Another example, if you change ISO from 100 to 1600 (which is 16x), so shutter speed should be divided by 16.

Then, you still retain the same exposure but you get faster shutter speed. Yay!

Recommendation

For most of the time, you would want to use ISO as low as possible, to provide smooth pictures without image noise. Normally, you change the ISO according to the light condition.

So when the day is sunny and bright, use the lowest ISO you have. The light is sufficient enough to get the correct exposure without compromising shutter speed or aperture.

When the day is cloudy where there is considerable amount of light, you may bump up your ISO around 400. With this, you may use any aperture that you wish to use and shutter speed can be relatively fast.

When you are shooting indoors and using flash will do no good (the subjects are far that the flash can’t reach it) or flash is prohibited, you may raise the ISO up to 800 or higher. If you are shooting indoor sports, you might end up with the highest ISO so you could get fast shutter speed. Although image noise may be visible and you might not like it, it is much better than having a blurry image because the shutter speed is not fast enough.

The same thing goes for night photography. Shooting at night either indoor or outdoor depends on the light situation. When it is dark, use high ISO and when it is quite bright, use low ISO.

In low light situation, the reason you want to raise the ISO is to avoid using too slow shutter speed which may in return will give you blurry images. However, using a tripod is another thing. Using a tripod adds stability to the camera thus allowing you to use slow shutter speed. Therefore, using a low ISO is viable this way.

Experiments

1. Find any subject in your home. Use manual mode [M] and set the shutter speed to 1/30s and aperture to the widest (smallest f-number). Vary your ISO from 100 to 1600.

2. Find any subject in your home. Use aperture priority mode ( [Av] or [A] ) and set it at the widest (smallest f-number). Vary your ISO from 100 to 1600. Make sure the exposure level is set at zero. To do this, hold down the Exposure Compensation button (the button has +/- symbol) and turn the main dial or you can half press the shutter button and turn the main dial.

Comment

1. You will notice the image gets brighter when you increase the ISO. This shows sensor gets more sensitive to the light as you increase the ISO.

2. You will notice the shutter speed gets faster when higher ISO is used. This shows you are able to use fast shutter speed at high ISO which is important in shooting at low light condition.

Conclusion

For most of the time, using the lowest ISO is very recommended because the resulting images will be smooth and less image noise. The change in ISO is made according to the light condition. Use low ISO when there is high amount of light and use high ISO when there is low amount of light to avoid too slow shutter speed which may give you blurry images.

In addition, more light is needed for good exposure at low ISO and less light is needed for good exposure at high ISO. So, you may use fast shutter speed or small aperture at higher ISO. In other words, using fast shutter speed or small aperture may result in underexposed images. Therefore, increasing ISO will compensate for the loss of light.

Last but not least, do have fun with photography.

Advertisements

2 Comments »

Any Comments?

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: