Teaching Myself By Teaching You Part III: Simple ISO

It’s pretty simple, ISO. If you’ve ever used film, you probably already know what it is, but to the digital crowd, its definition may be a little hazy. For me, all I knew was: Low ISO=clear photo , High ISO=grainy photo.

So let’s look a bit deeper into what ISO really is.

For a DSLR, the ISO represents the light sensitivity of the image sensor. “In terms of film, ISO is used as a rating system to tell you how sensitive the film is to light, or how fast the film is.  The lower the ISO number the more time the film needs to be exposed.  The faster the ISO film speed, less light is required to take a picture.” (here.) 

Digital cameras generally measure ISO in doubling increments (from low to high: iso200, iso400, iso800, iso1600) where a low ISO will provide a clearer photo, and a higher ISO will provide a “noisy” or grainy photo. Why would you want a grainy photo? Well, in certain cases, lighting is too low to capture a clear photo, so a higher ISO is necessary.

For example, I went to my city’s “Occupy WallStreet” general assembly a month and a half ago in order to take a few shots. The meeting took a few hours, and by the time it was over, the sun was long gone. Taking photos in a setting where the lighting is quickly diminishing, such as dusk, forces me to alter ISO in order to still be able to capture decent photos (I didn’t have my Speedlight on me).

This photo was taken using ISO400, it was kind of an overcast, dusky time of day.

But as the light diminished, I had to hike my ISO up to 800, then to 1600. Below is what an ISO1600 photo looks like:

Yay grainy! From my experience, ISO helps you to capture movement a little clearer in dim light. This crowd obviously could not stay still and the light was almost gone, so ISO1600 really was the only option. Good news is, there are programs out there that are especially made to get rid of that annoying “noise.” I just do not own anything like it. Honestly, the only thing I’ve ever done in order to make my grainy photos look a little clearer is upping the contrast and maybe using a sharpening mask.

If you find any cool, (even affordable!), programs that can help with the loud noise, let me know!

So What is ISO?

“ISO is a standard telling you how sensitive your film/digital sensor is to light.

  • Higher the ISO, the more sensitive the film/sensor is to light.
  • ISO speed affects allowed aperture and shutter speed combinations.
  • Higher the ISO, the more grainy or noisy pictures may appear.”

Yeah, sometimes I steal stuff from other sites. I can’t explain everything! 🙂


One thought on “Teaching Myself By Teaching You Part III: Simple ISO

  1. Something else about ISO is that the higher the ISO the faster the frame will capture, for instance, if you’re capturing sports, racing or other fast-paced motion, a low ISO will blur more (motion blur, not lens blur) and a higher ISO will capture the frame more clearly with less motion blur. The extreme of this is those photos where there’s rain or something and it appears frozen in time


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