Photo Tips: ISO

Posted on: Mon May 27, 2013

ISO 1600 © Andrew Newson

I’m hoping to give you some photo tips on a regular basis that should help your photography and this time around we will be looking at ISO. These will be included in the newsletter and if you wish to sign up for that, you can do so here.

ISO refers to the sensitivity (to light) of the digital image sensor. This is also true of film, except it was the sensitivity of the emulsion on the film rather than the image sensor. Most people remember buying 35mm film when going on holiday. If you were planning a trip somewhere hot and sunny you would have probably bought a lower ISO rated film like 100 or 200 because you would have had more light to use.

The lower the ISO rating the more light that is needed to achieve a well exposed photograph. In turn the higher the ISO rating the less light that that is need to achieve a well exposed photograph.

There are some quality issues to watch out for though, the higher the ISO the more digital noise you will get, a sort of grainy effect on your images. So to achieve the best results you always need to shoot at the lowest ISO rating that is possible for the shot.

I always set my ISO first. I may need to revisit this if I can’t achieve the results I want, but it’s always the very first thing I do.

I have a very broad guideline of what ISO setting I should use for what conditions…

Really bright sunny day = ISO: 100-200
Bright day = ISO: 200-400
Overcast Day = ISO: 400-800
Indoor/Artificial Light = ISO: 800+

These are just a broad guideline though, take sports photography for example where you need to achieve a fast shutter speed to freeze the action. Let’s say it’s an overcast day where I have suggested ISO 400-800, well it’s probably going to be the upper limit of 800 in this scenario.

Also landscapes, where generally it is thought that first and last light are the best for this type of photography. So you are shooting in relatively low light, so you would crank up the ISO, right!? Nope, not this time, you would use a low ISO to achieve maximum quality, probably the lowest setting your camera has (usually 100 or 200). This means you will be needing a longer shutter speed, but the landscape isn’t going anywhere fast so you can use a tripod and a longer exposure and this will give you the best results.

Low ISO with long shutter speed © Andrew Newson

Having said there are some quality issues when pushing the ISO, which is definitely true, modern cameras are getting better and better at being able to shoot at high ISO levels with pretty good image quality retained. So you do need to be a little careful but actually there are definitely scenarios when you will want to really crank it up to get the best shot.

Sometimes in fact you won’t have any other option, I’m thinking of a concert for example. If you see one on the TV you will see flash guns going off all over the stadium, these are only going to illuminate the back of the persons head standing directly in front of you. So in this scenario turning the flash off and using a high ISO setting is definitely your best option.

Sometimes flash can really spoil the atmosphere of a photo too, say at a party. You put the flash on and suddenly the whole scene is a wash with light and all of the atmosphere has been sucked out of the shot. Again, another scenario where it might be best to turn off the flash and go with a high ISO. The high ISO will be able to capture the ambiance of the available light at the party.

For those more advanced users you could try using a small amount of flash (think flash compensation) to illuminate your subject and a high ISO to capture the available light too.