Day 60: What Does a Stop of Light Mean?

It was my senior year in high school and I was sitting in Choir. Over the years, you would hear about someone going on “Vocal Rest” for the summer and gaining an impressive 2-3 notes on their range. “I didn’t talk for three months and then I was able to sing three notes higher than before!” Well we were back in Choir and our director wanted to know if anything fun happened over the summer. One of my classmates eagerly raised her hand and announced: “I went on vocal rest this summer and I gained three octaves on my range.”

With a furrowed brow I thought “WAT??” I wanted to say “Girlfriend, you know an octave is EIGHT NOTES? You’re telling me you gained 24 notes??” With a piano having a total of seven and the average human can handle, on average, two octaves to begin with, her claim to now have a five octave range was nuts. Ultimately, however, she just didn’t know what an octave was.

Well, sixteen years later and I hear the same thing quite often, although this time, it’s with lighting stops.

I hear photographers say something along the lines of “It was a touch underexposed, so I bumped it up a few stops and I was good.”

“A few stops?!” I think. That’s like saying “You’re a tad flat, let’s have you come up an octave.” or “This needs a touch more cinnamon, let’s add a cup.” Nooooo what? Finally, I asked someone (very politely) “What do you mean a few stops?”

And I finally learned, they meant a few turns of the shutter dial.

So, let’s discuss what a stop of light actually is.

A stop is the way we measure light. Similar to saying “The store is three miles away” or “The recipe calls for two tablespoons.” It’s a term of measurement and it simply means twice the amount of light as the previous image. Or, half the amount of light as the previous image. Look at the following images. They’re each a stop apart.

If we are working with ISO, a stop of light can mean from 200 to 400 or from 400 to 800… or from 800 to 1600.

When we are working with shutter speeds, that can mean from 1/125 to 1/250 then to 1/500.

When we are working with aperture values, that can mean F/1.4 to F/2 to F/2.8 to F/4 etc.

Let’s say you need to keep the same exposure but you need to bump your ISO from 200 to 400, but then you also need to make up for that stop of light. You can then increase your F stop value from 2.0 to 2.8 and your exposure will be the exact same as before.

There you have it! It’s so easy of a concept to get and once you know what your stop values are for each setting (ISO, AV, Shutter), you’re golden. You can manage your ratios and talk stop like a pro.

Day 98 is currently reserved for any questions you have throughout the 100 days. To submit a question, please click here!¬† If you’re interested in supporting this project, please share, PIN and comment! Any other questions, comments or ideas, please feel free to email me at denise(at)denisekaris(dot)com

Denise Karis is an Arizona photographer who enjoys musicals, Doctor Who and breakfast burritos. IG @denisekaris