Get to Know ISO

What is ISO?

ISO controls the sensitivity of your camera’s sensor to light (the sensor is where the photograph is created, doing the same job as film does in analogue cameras).

Where is the camera sensor?

The camera sensor is placed in the back of your camera body (behind the shutter door). You will find a small marking on top of the camera that looks a little like the London underground sign, this is exactly where the sensor is placed inshide the camera.

What does ISO do?

ISO gives you the option to choose how sensitive the sensor is to light, meaning you can work better in low light situations.

How does it affect the look of the photograph?

ISO affects pixel appearance, making the pixels look bigger and more coarse the more sensitive it gets. It is best to use as low a sensitivity number as possible, this will keep your photos looking sharper…in daylight always use a low sensitivity number [100 – 400], As you get past 800 the amplified pixels become very noticeable in your photos.

Where do I find the button/s to control it?

All cameras vary slightly but you will be looking for the letters ISO either on your camera top menu/a button alongside it or on the settings menu screen on the back. If you have a canon your menu/screen may look slightly different, if you have another make of camera then it will be very different, however you should still be able to find the same settings in a similar place.

What do the numbers mean?

The numbers show you how sensitive the sensor is, the BIGGER the number the MORE sensitive you have made it. This diagram is a rough guide for what ISO to set your camera on if you are using your shutter speed on at least 1/60 without a tripod.

The lower the number, the less sensitive the image sensor and therefore the smoother the image, because there is less digital noise in the image. The higher the number (more sensitive) the harder the image sensor has to work to establish an effective image, which thereby produces more digital noise (those multi-colored speckles in the shadows and in the midtones).

(link to manuals)

What buttons are useful to help support its function?

ISO functions on its own, there aren’t any other buttons that support this function.


A couple of analogies that might help…

Think of the pixels on your camera sensor like your pupils……the less light there is, the bigger your pupils get.

If you wondered… I.S.O. stands for International Standards Organisation and is not a technical photographic term. It is simply a sensitivity rating standard that analogue camera films had to meet in order to make sure they were all the same sensitivity regardless of brand. The term has just translated over to digital, now referring to the sensor instead of  the film.