ISO is the setting on your camera that determines the light sensitivity of your sensor when making your image. The setting is numerical in value and usually runs in 100s and 1000s. The higher the number, the more sensitivity to light. Depending on your camera’s technical specifications, you can push this setting from a range of 100 (or below) to 6400 (and beyond). This does not, however, mean you should.
ISO means different things to different cameras. Back in the day, when we all used film, ISO was a solid number we could depend on no matter which camera body we picked up because it referred to the sensitivity (and size) of the grain of the film. But that isn’t true in a digital world. A ton of factors make up whether or not your camera performs well at 100, 1000 or 3600 ISO. I have two different Canon professional cameras in my bag and both handle the same ISO with different results. It all has to do with technology advancement (newer sensors can perform better at higher ISOs), size of sensor, type of sensor, manufacturer tweaks and even software handling of the finished image. In other words, stuff that likes to get in the way of art! I’m not going to get into that here and if you want to know more about such things, I recommend an awesome website http://www.dpreview.com/forums/. These folks love to talk numbers, specs and stats and talk them well. Once I make a decision to buy a certain camera, I could care less about the numbers — I’m more into using my equipment and twisting the features to my advantage.
So how do you twist ISO to your advantage? Well, you learn the guidelines and then experiment so you know what your equipment can handle in a given situation. There are some basics, so let’s cover those first.
Low ISO (100 to 400). In a digital world, 100 to 400 ISO is low. This means your camera is less sensitive to available light and the resulting image will have less grain, or noise, and fewer artifacts. However, the trade off is slower shutter speeds which are not conducive to action photos. In my work, I use low ISO for still studio shots or bright outdoor shots. Both of my cameras handle 100 to 400 ISO very well. In my opinion, my 5D Mark II shows very little difference between the two settings, so I always opt for the higher setting.
Medium ISO (400 to 1000). Most modern digital DSLRs can shoot in this range and stay in a happy place. Settings in this range are a generally conducive to acceptable shutter speeds for well lit action and show a minimum of noise, grain and artifact. This is a good setting for indoor or outdoor work with slow to moderate movement of a subject.
High ISO (1000 and above). My 5D Mark II can push the limits of ISO to places unimaginable because it has some kind of digital software compensation that can actually make it even more sensitive — BUT there is a limit where grain and noise gets to be too much to make a good image. For this camera, it’s up there. I’ve shot images at 3600 and beyond that were usable. I, personally, do not like to go above 1600 to 2000 —even with my 5D Mark II — unless there is no other way to get the image. I will use 1600-2000 for some of my indoor arena work when shooting reining horses. I have used ISOs of 2000 and above when I have had no available flash (or flash wasn’t allowed) and I was shooting indoors. This past November, I pushed the limits of my camera (and my pulse) at a candlelight wedding ceremony.
Next time, I will talk more about some specific situations and why I chose to use the specific ISO I did.
Your Mission (should you chose to accept it): Now that we have the very basics covered, it’s time for YOU to DO rather than just read! This week, I want you to locate the ISO setting on your camera (I do believe all DSLRs have one) and learn how to change it. Once you’ve accomplished that, pick one indoor and one outdoor situation and take a series of images in each situation changing the ISO to at least three different settings. Compare these images on your computer at 100% size (grain doesn’t always show on compressed images). Print the images to see how much difference shows when printed because this WILL be different than on your monitor. DO NOT post process for the comparison or the printing.
This image was shot with my Canon 1D Mark II N. This camera has a high end ISO of about 1600. In my opinion, you get above that, the grain is not acceptable. This image was taken with a Sigma 70-200 zoom 2.8 lens. Shutter speed is 1/160th at 2.8 with an ISO of 1250. This image has not had a lot of post processing so notice the color balance is very warm and there is some noise in the shadows.
This is a silver dee from Bob’s Custom Saddles. I use ISO of 100 to shoot silver because I want as little noise or grain as possible. The subject here is static and I use studio lighting which I can adjust accordingly. When shooting product images like this, I like to adjust the lighting situation to fit the ISO and aperture I need versus the other way around.