Moving Toward Manual Settings: Understanding ISO

If you are new to photography, or don’t have a clean grasp of manual settings, go back and read the first two installments of this series: Understanding Aperture and Understanding Shutter Speed and then come on over to learn about ISO.

1. What is ISO?
Your ISO allows you to take pictures in low light situations.
It is basically a measure of your digital sensor’s sensitivity to light. The higher the number, the more sensitive to light your sensor becomes.

2. What is a Sensor?
Your digital sensor is where your image is exposed (aka RECORDED).

3. What is Exposure?
Exposure is light recorded on your digital camera sensor.

4. How Does ISO Affect the Final Image?
Well, if ISO determines how sensitive your sensor is to light, and your sensor records the light (a fancy way to say records the finished image) then that sensitivity of the sensor is basically going to determine (along with your aperture which determines how MUCH light hits the sensor and shutter speed: which determines the DURATION OF TIME the light is exposed to the sensor) how bright your image will be (how much light will be absorbed by the sensor).

5. What is Digital Noise?
Film is composed of lots of little circles that make up the GRAIN of the film. Digital photography is similar, except for that our little circles aren’t circles at all, they’re squares. . . a gazillion little squares that come together to create an image. Sometimes those little squares in the image become slightly visible and this is referred to as NOISE. 

6. What Does Digital Noise Have to do With ISO?
Well, digital noise increases with ISO. The lower the ISO the less noise you will see (and most likely you won’t see any at all). As your ISO increases, the noise level does as well. This noise level most likely will not become significant until your ISO reaches numbers of 800 or higher (depending on your camera). Rumor has it that the new Nikon D3 has magic ISO capacities that allow for ISO’s of 1600 and even higher with NO NOTICEABLE noise whatsoever. 

HERE ARE SOME BASIC GUIDELINES FOR SETTING ISO: please don’t be intimidated by the mad drawings. What you see below is the result of YEARS of dedicated study and commitment!

On a sunny day – set you ISO low, try 200 ISO.

On a cloudy day – bump up your ISO a little, 400 might be a good starting point.

If it’s dimly lit, indoors, evening and you are not using a flash, dial up a higher ISO – somewhere in the vicinity of 800 could work. Remember that the higher your ISO, the lower the quality of your image. That said, it’s important to keep in mind that sometimes grain can add a fun artistic edge to a photo. 

Here’s your ISO assignment:
Test your camera’s image quality at different ISO settings. Set your camera to AV (Aperture Priority). Set your aperture to no lower than 4. . . preferably around 5.6 the purpose of this assignment is not to mess with exposure, composition or depth of field. The goal is to test your camera’s ISO capacities and how it holds up under the pressure of high ISO’s. Step outside into the open shade. Shoot an image at 100 ISO and move up incrementally through your camera’s available ISO’s all the way until you reach your camera’s maximum ISO. . . don’t worry, your camera should make up for the extra sensitivity of the sensor by shortening the shutter speed. Upload the images and check the quality. If you really want to get the most out of this assignment, Print each image to at least 8×10 or even 16×20. You’ll be glad you did if you really want to know your camera’s susceptibility to digital noise. Study the images and determine what you feel is a good ISO range that still maintains image quality for your particular camera.

You’re so close to achieving the creative freedom and confidence as a photographer that manual settings allows.

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