Steve's Photography Tips: What Is ISO?
Most all cameras these days have an ISO setting. Even the “point-and-shoot” type cameras have this setting, although it may not have as many choices as the DSLR type cameras may have. But what does it mean?
Journey with me if you will back to the old days of film photography. Yes, some people still shoot on film, making the old days still the current days. But those people are hard to find these days. And they probably aren’t coming for photography tips to someone like me, either.
Anyway, back in the old days we used this stuff in our cameras called “film.” It was on a little roll, and it was finite. When you ran out of film, you stopped taking pictures. At least until you could put in a new roll of film. And then you had to pay to have it developed, too.
And these rolls of film each had ISO ratings. The standard ratings were 64, 100, 200, 400, and 800. Those numbers were also known as film speed. The higher the number, the “faster” the film. Why? Because the number had to do with the film’s sensitivity to light. The lower the number, the less sensitive the film was to light, meaning that you could shoot in brighter light without any problems. The higher numbers were more sensitive, so they were better for lower light conditions. Of course, some of that could be compensated for with aperture and shutter settings as well. And a good tripod. (For a more technical, detailed explanation of ISO, you might wish to read this entry at Wikipedia, if that’s your thing.)
In those days, I would typically shoot with ISO 200 film in my Pentax K1000 camera. Especially for our trips to Walt Disney World, that speed seemed to be a good balance for shots in the bright Florida sun, or overcast skies, or even an occasional nighttime photo. Sometimes, I would get adventurous and throw in a roll of ISO 400, if I thought I would be taking several photos on that roll in the evening or nighttime hours.
Here are a few examples from those photos. The first and the third used ISO 200 film, while the middle one used ISO 400.
The Florida sun highlights the spires of Big Thunder Mountain on a bright summer day.
This evening photo of Spaceship Earth and the giant palm tree that used to be behind Earth Station required a steady hand.
For this nighttime photo of Echo Lake at Disney-MGM Studios (now Disney’s Hollywood Studios), I balanced the camera on a rail near the lake for the long exposure.
I could share several more examples, but you can see them all in the Looking Back posts of old photos. Some were taken during the daytime, some in the evening, and some at night. And most with film with the same ISO. Because it was difficult to go back and forth back then.
These days, as mentioned earlier, most all of these newfangled digital cameras have ISO settings. With the simple push of a couple of buttons, you can switch from ISO 200 to ISO 3200 or higher. Which is quite a change from those old days.
Going back to film for just a minute, when you selected a certain film speed, you were most likely committed to it for 24 or 36 frames, depending on the size of the roll of film you were using. I suppose you could wind the film most of the way back in the canister and switch to a different roll of film, and then somehow roll the film back to where you had left off when you took it out of the camera, but that would have been very tricky, and I never wanted to give it a try. Or you could have two cameras with two different speed films, but that was expensive, too. So if you started a roll of ISO 400 film, you better be prepared to finish it. And also, the faster the film, usually the more expensive it was. I never used anything above ISO 400. And I rarely heard of any casual photographers using anything above ISO 800.
But as I just mentioned, you can now change the ISO setting for each photo you take, depending on the conditions when you are taking the photo. Out in the bright sun? Switch to 100. Go inside for a moment? Switch to 1600. Go back out into the clouds? Try 200.
As you can see from those examples, as a general rule you would use a higher ISO setting the darker your shooting environment gets. Low numbers for sunny days, high numbers for nighttime or inside away from the sun. But that isn’t always the case.
There are a few limitations. Or more specifically, one limitation: Photo noise. This also corresponds to the old film days. Back then, the higher ISO films had more film grain, which are the little dots that make the photo look grainy, or not exactly smooth, if you didn’t know. You can see a little of that in some of the photos that I posted above. And you can see where I somewhat simulated that look in this portrait of Laura. In those film days, sometimes people would actually use higher ISO film on purpose, just to get that grainy look, as it could be artistic at times.
But these days, most people seem to prefer a nice, smooth, noise-free look to their photos. And just as higher ISO films had more grain, higher ISO settings on digital cameras generally have more noise. Yes, that can be corrected, sometimes quite effectively, with post-processing that is available these days, but it is something to consider.
So here are a couple of examples, specifically focusing on nighttime photos, when you might be wondering what ISO setting to use on your camera. First up is this nighttime photo from the Magic Kingdom:
One good thing about digital camera photos is that most of them retain the shooting settings, so that you can go back and check that later on. For this photo, I used a setting of ISO 1000 because of the darkness of night. That would vary some in different sections of the park, depending on how much lighting there is in that area. In aperture priority mode (more about that at another time), I had my aperture wide open at f/1.8, and I had also set the exposure bias to -0.7, because I knew the lights would be pretty bright. All of that gave a shutter speed, set automatically by the camera in aperture priority mode, of 1/20 second. Which is approaching the limit of how long I can hold the camera steady by hand without using a tripod.
Now, here’s a different photo:
For this photo, I used a much lower setting of ISO 400. And actually, I probably could have gone lower than that. I used a tripod for this one, which allowed me to set the aperture to f/11 and use a 10-second exposure. No way I could have held the camera steady that long by hand. And even though the Center Street photo above looks pretty good “cleaned up,” this one took almost no processing at all, thanks in large part to the lower ISO setting. In the large version, you can still make out a little noise, but nothing like what would have been visible at ISO 1600 or higher.
So as you can see, your ISO setting depends on more than just the amount of light that is available. What sort of look you are going for and what shooting conditions are available can also play a large part in your selection. While sometimes a higher ISO setting is necessary, hoping that you can remove some noise later on, I always try to use the lowest ISO setting possible, even if that means using a tripod.
Questions? Further comments? Different tips or tricks? Leave them in the comments below!
