Life, Love and Part 2: ISO speed

In a previous article I discussed how changing the shutter speed can greatly change the look and feel of an image. And once you tried a few of my suggested photos you immediately became entranced with my wisdom and I gained some street cred. But let me remind you, I’m a hobbyist at best and my amazing portfolio represents the few successes of literally thousands of failures, which sadly is a better track record than my dating life.

In this article we move on to a necessary counterpart to shutter speed: ISO speed. Remember how last time I asked you to compare the camera to an eyeball, with the shutters being the eyelids? Well this time you can still compare the camera to an eyeball but it will just get confusing when I talk about apertures. But what the heck, most things in life are confusing like feelings from gym class and swimsuits for fat people.

If the camera is an eye then the size of your pupil could be considered the ISO speed. Now let me explain why this is confusing, to be more exact the size of your pupil is more likely to be the aperture, or the size of the hole that lets the light through, but the sensitivity of your eye at different stages of pupil size makes more sense when analyzing ISO speed.

Think about the time you saw the matinee on a bright summer day. As soon as you left the theater you walked outside and everything was bright white and you screamed like a girl. This is ISO speed. At low speeds like 100 the film is not very sensitive to light. This is like being out at the pool at high noon with eyes wide open. When you were in the theater watching the movie your eyes were more like ISO at 800 or even 1600. When you were running from the cops through the moonlit forest at midnight because you failed to realize that no meant no your eyes were adjusted to the darkness and you could pretty much see the gist of your environment. This would be the equivalent of ISO speed at very high speeds like 1600 or even 3200.

Understand? Probably not, an easier way to understand it is just to know that ISO speed is how sensitive the film is to light. At lower speeds its less sensitive which means that it can capture an image just fine at noon day. At higher speeds it means it is very sensitive. This makes it possible to shoot better night shots.

ISO can do a few things for you. For one it can work to balance out your shutter speed. If you need to shoot something with a faster shutter around evening time you can set the ISO speed to be more sensitive (say 800 or 1600) making the shot brighter. Conversely you can set the ISO to 100 if you are going to leave the shutter open longer to mitigate light saturation.

For a while I used to shoot a lot of night shots at 1600. They were mostly of my neighbors and I didn’t want the flash to wake them or reflect of the bedroom window that separated us. The advantage was I could use a higher shutter speed in a dark environment and not have to worry about motion blur. Also flashes can drown out colors, reflect off surfaces and can make environments look very flat. The downside is that the end picture can be very grainy. Don’t get me wrong, you can still get some great pictures regardless of grain, but like garlic, use sparingly.

If you want a fun exercise go up on a hill that looks down on your home town at night. Set up your tripod and your camera and then set your shutter speed to about 3” or 5”. Now take a series of photos with varying ISO speeds. As the speeds increase you will begin to see a warm red glow engulf the city. This is another way you can affect the mood of your images.

When the ISO is lower your images fend off light giving it a colder paler look. At higher speeds the image tends to warm up, giving into oranges, yellows and reds. For instance if you take a picture of elderly people in swimsuits running through sprinklers in the summer months at mid day you’ll be tempted to shoot at a lower ISO to avoid saturation. Unfortunately someone will say “Good heck! Those poor old folk are running about in the winter!” This is due to what I mentioned before, most images at 100 ISO tend to have a cold stony feel to them. So now instead set the image to a high ISO, say 200 or even 400 and now set your shutter speed even higher. This will cause the image to have a warmer feel but the higher shutter speed control the amount of light coming through.

Let me give another example. If you’ve been a good study you’ve already gone out and played with your shutter speed but been horrified…HORRIFIED to find that often shadows are underexposed (too dark) and lit areas have been overexposed (too light). You’ve obviously been up late nights wondering how you can meet in the middle so that shadows aren’t too dark and lit areas aren’t all crazy white? The problem is this: When you focus your camera on your subject it adjusts to make sure the subject is lit enough (because even though you are playing with shutter speeds your camera will often still control things like ISO and aperture and adjust them accordingly. It’s like when you think you are using the big potty but you’re really using the little potty). So when the picture takes your subject is lit well but the shadows and sunlit areas are unintelligible because the camera didn’t care to take them into account. The answer my friend is ISO. If you’ve got shadows in the picture raise the ISO speed. If you’ve got pockets of light around lower your ISO.

You’ll run into countless opportunities to complain that your image is too dark or too light, if you’ve got a digital camera simply change the ISO and take the image again. If its still too extreme then give up, you’re clearly not a photographer. ISO is fairly intuitive and you’ll be able to quickly figure out how to make it complement shutter speeds. Apertures however are a different story.