Shooting In Manual Mode: ISO
Note: This is part 2 of a 5-part tutorial series for beginners. Articles are as follows:
- Part I: Shooting In Manual Mode: Intro
Part II: Shooting In Manual Mode: ISO
Part III: Shooting In Manual Mode: Shutter Speed / Exposure Time
Part IV: Shooting In Manual Mode: Aperture
Part V: Shooting In Manual Mode: Conclusion (Exposure Triangle)
One thing that we humans do not fully understand is how severe of an adjustment our eyes and brains make when walking from outside to inside or vice versa. You don’t really have to think about it. When you walk outside, you say “Oooh, it’s bright out here,” and then your eyes adjust within ten seconds and everything’s fine. Even in a well-lit home with sunlight streaming through the windows in the middle of the day, the world outside your home is literally hundreds of times brighter than the world inside your home. We do not realize the full extent of this because our eyes and brains adjust to these differences very quickly and accurately. Your camera, on the other hand, requires you to guide it through these changes. Typically, a camera attempts to make up for these differences by using the inbuilt flash when indoors, because nearly every camera is not well-equipped for shooting indoors. If I’m shooting on Manual Mode outdoors and I walk inside without adjusting my camera at all, the resulting indoor images will be severely underexposed (read: every pixel will be black) and completely unusable.
ISO is one of the easiest concepts to understand in photography: the higher the ISO value, the more sensitive your camera is to light. All other things being equal, a higher ISO will produce a brighter image. In order to understand ISO, one must have a basic understanding of film speed. Higher speed film (higher number) is more sensitive to light, so it can be used in situations with lower levels of light, such as indoors with no flash. High speed film (or high ISO values) make it easier to shoot in most kinds of light, but as always, anything that makes it easier to shoot also comes burdened with a sacrifice. This is a steadfast rule in the world of photography; never forget it.
The sacrifice one makes when using higher ISO values is that the photograph/image is much lower quality all-around. One could use ISO 800 for outdoor photography, but that is extremely rare because photographs taken with higher speed film are more “grainy” and are lacking some of the detail. If your lighting situation can afford you using ISO 100, you should try to stick with that. Images captured with a high ISO rating (800 or greater is a good rule of thumb for most cameras) have much higher levels of image noise. Regarding images, noise has the typical definition: anything random and unwanted in your image. It is basically a bunch of dots/specks that interrupt your image and keep it from being as sharp as it could be.
Here are a couple rules of thumb:
- Use ISO values that are multiples of 100. Try to stay away from ISO 125, 160, 250, and so forth. ISO ratings that are divisible by 100 are a “full stop” apart. All other ISO values are digitally interpolated and are therefore believed to be inferior. This point has been debated quite a bit, and different people come to different conclusions based on the model of camera that is tested.
- ISO should be the last thing you modify in a low light situation. Again–this is debatable. But here is how I come to this conclusion: no matter what other factors are present (tripod, lighting), a higher ISO value will degrade your image quality. The shutter speed and aperture may change the look and emotion of your photograph, but a higher ISO will always degrade the quality. Always. Some people may argue this point and say that they “like” grain/noise. That is a matter of taste, but a noisy image is undoubtedly a lower quality image. Keep your ISO as low as the lighting situation will allow. I have a very low noise camera model, and I still try to never go above 400 ISO.
- Test your ISO values while viewing your images at 100%. Look, if you want to be sure that ISO 1000 is “too high” for you to use, capture a bunch of images at ISO 1000, and look at them on your PC at 100%. This means that every pixel in the image will take up one pixel on your monitor. In order to do this, you will most likely have to zoom in so far that you will not even be able to tell which part of the image you are viewing. That’s fine; ignore all that. Check the quality of the image file without any regard for it as a photograph (remember, this is just for testing purposes). Is there a lot of noise? Come to your own conclusions. Draw your own line in the sand about what values you will not use. I personally try to not go above ISO 400 (which is unfortunately the ‘default’ value for a lot of cameras on auto mode), and I definitely do not go above ISO 800 unless the circumstances are extremely dire.
- Buying a better lens will not help. The way your camera behaves at different ISO values will not change if you buy a $1000 lens. It is a function of your camera’s sensor and there is nothing you can do to change that. Buying an expensive lens may afford you the ability to sometimes use a lower ISO value (due to some other factors covered in different sections of this tutorial), but it will not change how your camera behaves at a given ISO.