Yesterday, we imagined a faucet when we learned about shutter speed. We learned to fill our cup by controlling our shutter speed. Leave the faucet running too long, the cup overflows – your image is overexposed. Not long enough, the cup doesn’t fill and your image is underexposed.
If shutter speed refers to how long you leave the water on to fill the cup, ISO refers to the flow of water.
ISO is a measurement of how sensitive your camera is to light.
The lower the number, the lower your camera’s response to light. The higher number, the more sensitive it is to light. And the pros say “I. S. O.” not /eye-so/. ISO stands for International Organization for Standardization – and for the purposes of languages around the world has adopted the acronym ISO. Think of ISO like receptors of light – you can have 100 receptors on your sensor or 400 or more…
If ISO 100 is a slow flow of water, each increment doubly increases the flow: 200, 400, 800, 1600, 3200, 6400 +
The higher the ISO, the faster the water pours out of your faucet. And in direct relation – the higher the ISO, the faster you can shoot.
If the water comes out very fast, it isn’t necessary to leave the faucet on very long to fill your cup.
If the water flows more slowly, you must leave the faucet running for a longer period to fill the same cup.
Together, ISO and shutter speed control how much light gets to your sensor.
But there is a trade off. With increased ISO comes quality deterioration of what you capture. The higher the ISO, the more noise (sometimes still called grain from the good ol’ film days) you will see in your photos. So while ISO of 100 or 200 may look like glass, an ISO of 1600 may look like sand.
Most photographers try to shoot with as low ISO as possible, but seek machines that will give them flexibility to use higher ISOs without visible noisy, grainy photos. This sensor quality makes big price point difference when shopping for a camera! It is a big reason why a camera costs $1000 or $5000. It’s also why wedding photographers can get beautiful clear photos in a darker church while most consumer cameras get noisy images – pro photographers invest in machines with sensors that handle ISO better. The lower the quality of a camera’s sensor, the sooner destructive grain becomes an issue at lower ISOs.
“So, why are my photos better outdoors than indoors?”
Because generally, outdoor means better light. Even inexpensive cameras can handle well-lit situations easily. As the light decreases, so does the performance of most cameras. Outside, you can shoot fast at a low ISO. Indoors, you (or your camera) often must compensate by increasing ISO and slowing shutter speed to allow in more light.
High ISO = noise. Slow shutter = blur. It’s the perfect recipe for disaster. If you have an inexpensive camera that doesn’t handle noise well, try to keep your photo opps outdoors or during well-lit daylight hours. You’ll be much happier with your results. Don’t be afraid to direct your subjects to a place you know your camera can perform better.
Time to play!
Grab that trusty camera, and put it on program mode (not Auto, which will choose the ISO for you).
Set your ISO to the lowest number you can see. On Nikon that will be 200, on Canon it will be 100. Your camera may vary.
Take a picture, and note the shutter speed your camera chooses.
Stay in the same place, shoot the same subject again.
Move the dial one notch – doubling your ISO to 400 or 200. (Some cameras may have middle ISO numbers, but for this exercise, double the ISO.)
Take a photo, and note the new shutter speed.
You will notice – each increase is twice as sensitive and each decrease is half as sensitive. Without getting too technical at this point, it means you can get the same mathematical exposure by adjusting the ISO and shutter speed in doubles and halves.
Imagine the correct exposure of an image is ISO 400 at 1/100 sec.
You can halve the ISO and double the shutter and get the same exposure – ISO 200 at 1/50 sec. Using our analogy, you reduce the flow of water in half, you have to leave the faucet on twice as long to get the same results.
Likewise you could double the ISO and halve the shutter speed – ISO 800 at 1/200 sec. Meaning, you double the flow of water out of the faucet, and you only have to leave the faucet on half the amount of time.
In the above example, what’s the correct shutter speed if we move the ISO to 1600?
Which ISO would we choose if our shutter speed is 1/800 second?
So far, so good? Tomorrow begins the last piece of the technical puzzle!
Please visit my girls who are sharing this 31 Days journey with us:
31 Days of Grace :: Chatting at the Sky
31 Days to an Inspired Table ::Â My First Kitchen
31 Days to a Less Messy Nest ::Â Nesting Place
31 Days of Living Simply ::Â Remodeling This Life
31 Days of Autumn Bliss ::Â The Inspired Room
31 Days to More. . .With Less ::Â Beauty and Bedlam
31 Days to a Better Photo ::Â My 3 Boybarians
31 Days to Stress Free Entertaining ::Â Reluctant Entertainer