Shutter speed and aperture are fairly straightforward to understand, the size of the whole to let in light and how fast we the shutter opens and closes. So, ISO, this little acronym stumps a lot of people but how I see this might help.
Last night I had one too many drinks and got a little bit light headed and blurry eyed, the effects of cheap wine, not a lot of food and ten pounds. This was worth every penny until the alarm went off this morning. I climbed out of bed, opened the curtains and the sun flooded into my room in all its glorious radiant yellows and golds, and my eyes, being those perfectly designed viewing holes let all this lovely light flood in. Unfortunately, the effect of alcohol had made them less than perfect and those very bright sun rays traveled straight through to the back of my head and probably carried on after that. I squinted to reduce the light entering (reduced my aperture), this helped but, the night before had made my eyes a little bit too sensitive.
I now have a theory, that alcohol is a chemical method to increase the ISO in my eyeballs. On the other hand, sat at work all day staring at a computer screen seems to reduce eyeball sensitivity quite well. Luckily, my camera does not need alcohol to increase the sensitivity to light, it has an ISO dial that goes from 100 to 6400, some cameras go way high than this.
What does this mean, you may ask? Imagine wandering around in the dark without a torch with that lovely effect of a hangover, your eyes are extra sensitive, you may see a little better. This applies to cameras. You can up the ISO a little higher to make the camera a little bit more sensitive to light but, try and use the shutter speed and aperture first. Leave the ISO until last unless there is a particular reason, for example, shooting the night sky.
With this great little ISO button there has to be a downfall, is there? Yes, there is. The higher the ISO the more you will lose the sharpness of the photo and the image will look grainy. Try it, take a photo with the setting, Aperture: f22 Shutter Speed: as fast as you can get and up the ISO to as high as you can get it. Download the photo your computer and zoom in. There you will see the loss of quality. Also worth trying the opposite, ISO: 100, a slow shutter speed and check the quality. Obviously, for those slow shutter speeds, a tripod is going to be needed.
Things to bear in mind with the ISO setting.
- Higher the ISO, the more grainy the photo
- Lower the ISO, the more likely you will need a tripod
- If you do want a clean photo and can not use a tripod or flash, rest on something or lean against something. One notch down on the ISO can make a huge amount of difference, especially when you view the photo full size or you need to do some post editing.
- A lot of modern good cameras have a method to reduce the iSO grain from low light, don’t really on this. Better to work with a low ISO than to get home and see what you hoped you would not see, grain.
For those wondering what ISO actually stands for it is: International Standards Organisation.