You’ve seen the ISO button, but do you know what it does?
ISO can be thought of as the control you have over the level of how sensitive your camera’s sensor is to light.
That said – the more light you have, less sensitive your camera’s sensor needs to be (lower ISO). Conversely, when shooting in darker conditions, you may need to photograph at a higher ISO setting.
Of course, it’s never that simple…and after-all, if using higher ISO settings would yield us faster shutter speeds, then why wouldn’t we ALWAYS shoot at high ISOs?
There are two primary reasons why you don’t want to shoot at high ISO settings.
- Noise/grain – Do you hate when your photos come out noisy? Many photographers strive to have as “clean” of photos as possible with little noise. There is a direct relationship between noise and ISO. The higher the ISO setting, the more noise you will see in your photos. Read this tutorial if you need to remove some grain from your photos.
How much noise? That will depend on your camera.
One of the primary areas that higher end cameras significantly outperform entry level models is how well they handle noise.
- Dynamic Range – The higher the ISO setting the lower the dynamic range you will get in your photos. What’s dynamic range? Think of it as the range of tonality captured in a photograph. Think of a sunset for a minute, at sunset you have dark and shadow areas and you also have a bright sky/sun…in that example there is very large range of tones and by working at a lower ISO you will be able to capture more of that range.
Where should your ISO setting be?
It depends & it’ll constantly be changing too.
My general rule of thumb is simple really…keep it as low as possible. But, what does that mean?
It means, unless you are deliberately trying to product noisy photos, shoot at the lowest ISO setting that you’ll still have a fast enough shutter speed.
…key phrase is “fast enough” shutter speed.
If you are convinced you don’t want any noise in your photos so you keep your ISO at 100 but then your settings are 1/30th a second with an 85mm lens…you WILL get a blurry photo.
When this happens to you, you have two options to raise your shutter speed.
- Raise ISO or
- Shoot at a wider aperture
How high is too high?
I always say I’d rather have a noisy photo than a blurry photo. So if need be, don’t be afraid to crank up the ISO! There are tools available in Lightroom, and other places, that you can easily reduce some of the noise but you can’t fix a blurry photo!
I hope this quick read helps clear some confusion over ISO and lets you know what you really need to know about the ISO setting.
Read this tutorial too if ISO still has you a bit confused.