ISO (I.S.O.) is the abbreviation for the International Organization of Standardization, a governing body based in Europe that provides the standards for a wide variety of subjects.
In 35mm film photography ISO (or ASA) was the indication of how sensitive a film was to light. It was measured in numbers and you have probably seen them on the film boxes… there was ASA 100, 200, 400, 800 etc. The lower the number the lower the sensitivity of the film and the finer the grain in the shots you’re taking.
In Digital Photography there is only ISO. ISO measures the sensitivity of the image sensor. The same principles apply as in film photography – the lower the number the less sensitive your camera is to light and the finer the grain. Higher ISO settings are generally used in darker situations to get faster shutter speeds (for example an indoor sports event when you want to freeze the action in lower light) – however the cost is more digital noise (fine grain or colored spots) in your shots. 100 ISO is generally accepted as the ‘normal’ and will produce an image with very little noise/grain.
Most people tend to keep their digital cameras in ‘Auto Mode’ where the camera selects the appropriate ISO setting depending upon the conditions you’re shooting in (it will try to keep it as low as possible) but most cameras also give you the opportunity to select your own ISO. I am not an advocate of auto ISO, but my suggestion, start with AUTO when you are VERY new with the digital camera, but start playing with setting your ISO settings to help master the exposure triangle of shutter speeds, aperture and ISO. It will give you more freedom and allow you to be more creative.
When you do override your camera and choose a specific ISO you’ll notice that it impacts the aperture and shutter speed needed for a well exposed shot. For example – if you bumped your ISO up from 100 to 400 you’ll notice that you can shoot at higher shutter speeds and/or smaller apertures in lower light situations.
When choosing the ISO setting I generally ask myself the following four questions:
1. Light – Is the subject well lit?
2. Tripod – Am I using a tripod?
3. Moving Subject – Is my subject moving or stationary?
If there is plenty of light I will generally use a pretty low ISO rating. (50 or 100). However if it’s dark, or I don’t have a tripod and/or my subject is moving I might consider increasing the ISO as it will enable me to shoot with a faster shutter speed and still expose the shot well. Of course the trade-off of this increase in ISO will be noisier shots. But software like NIK Dfine will quickly, and easily eliminate noticeable noise.
Situations where you might need to push ISO to higher settings include:
· Indoor Sports Events – where your subject is moving fast yet you may have limited light available.
· Concerts – also low in light and often ‘no-flash’ zones
· Art Galleries, Churches etc.- many galleries have rules against using a flash and of course being indoors are not well lit.
· Birthday Parties – blowing out the candles in a dark room can give you a nice moody shot which would be ruined by a bright flash. Increasing the ISO can help capture the scene.
· Shooting night landscapes – maybe you are shooting northern lights or stars.
ISO is an important aspect of digital photography. To have an understanding of it, and want to gain more control of your digital camera… experiment with different settings and how they impact your images. The more you practice, the more you learn, the better you will become.
Getting The Correct Exposure For Beginners
Having the correct exposure is about having enough light in a photo. Over-exposed photos are bright, harsh and can look washed out. Whereas under-exposed photos are too dark to pick up on details
Shutter speed, aperture and ISO work together to bring out a nicely exposed photo. The three combined are called the "Exposure Triangle". But how do you go about getting the right exposure while taking manual control over all three aspects of the exposure triangle?
Here are steps I usually take to decide on the right setting for the photo I’m trying to achieve.
Step 1: Adjust the ISO first
When you’re shooting a series of photos in a consistent environment, there’s no need for you to constantly play around with the ISO.
Before you begin shooting, determine the ISO first (remember, the lower the better). A bright environment with plenty of light might just need an ISO of 100 or 200. Whereas an indoor environment would be 400 to 600, and night photography would require 800+.
Step 2: Figure out what you want to capture
Next, you would want to think about your subject. If it’s landscape, you would want to keep as much in focus, but still allow more light and details. In this case, choose an f16. Or if you wanted to create a narrow depth of field like a macro photo, you would have a wider aperture (like f1.8). Then, you would adjust the shutter speed accordingly.
Sometimes with moving objects, you might approach this the other way, thinking about shutter speed first before playing around with the aperture. Take a runner for example. If you wanted to capture them frozen, then you would need a faster shutter speed. Whereas if you wanted to create blurs from their movements, then you’d choose a slower shutter speed.
If changing the aperture and shutter speed isn’t creating the desired effect you want, you might need to go and adjust the ISO to a larger or smaller number. This allows you to play with your shutter speeds and aperture to help you get the desired result.
Now, these aren’t step you must follow every time, but it’s a good start for beginners. Adjusting the settings might be confusing initially, but lots of practice will have you turning those setting dials like a pro in no time.
If you would like to learn more about ISO, we have lots of one day composition workshops, weekend workshops in Niagara Falls and workshops to photograph northern lights on our Canadian Workshop Page. Click here to see those workshops.