Special Announcement

I’ve added a Photography Basics/Introduction To Photography class starting on Saturdays for the April series of classes.

Special Announcement

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A question that comes up a lot, especially during the Photography Basics/Introduction To Photography class, is why don’t the aperture ( F stop ) numbers double or half like the ISO and shutter speeds when moving in one-stop increments?
 

First, let’s clarify what a “stop” is.

A stop is an increment of one that doubles or halves, and we can apply it to aperture, shutter speed, and ISO.
 

In photography, ISO and shutter speed follow a simple doubling pattern because they scale linearly with each other.

When we double the ISO’s light sensitivity (100 → 200 → 400) or double the exposure time/shutter speed (1/250 → 1/125 → 1/60), the sensor or film receives twice as much exposure, which is equivalent to one full stop.
 

On the other side of the coin, if we halve those previous settings, the picture gets half as much exposure, which is still equivalent to one full stop.
 

In general, we could say that if we double the exposure or light sensitivity numbers, we make our photograph two times brighter; if we halve the exposure or light sensitivity numbers, we make our photograph two times darker.

Aperture, also known as f-stop, works differently because the f-number (f/2.8, f/4, f/5.6, etc.) doesn’t measure exposure directly.

It’s a ratio: the focal length of the lens divided by the diameter of the aperture opening.

What actually controls brightness is the area of that opening, not just the diameter.

Since the area of a circle changes with the square of the diameter, doubling the amount of light requires the aperture’s diameter to increase by the square root of two (≈1.414) rather than by 2.
 

That’s why the standard full-stop aperture sequence looks like:
 

f/1 → f/1.4 → f/2 → f/2.8 → f/4 → f/5.6 → f/8 → f/11 → f/16

Each stop multiplies the f-number by about 1.4, which changes the opening’s area by a factor of 2, giving you one stop more or less light.
 

So even though the numbers don’t double, the exposure caused by the lens still doubles or halves, just like shutter speed or ISO’s light sensitivity.

While knowing the science behind why aperture numbers don’t double or halve like shutter speed, and ISO may interest those who enjoy technical details, it’s more important to understand the compositional outcome.
 

Understanding that one stop of aperture changes exposure by a factor of two, effectively doubling or halving the brightness, is what matters for our images.
 

The science is secondary; what counts is understanding the compositional cause-and-effect between aperture and how our picture looks.

The next round of Photography Basics/Introduction To Photography classes starts soon. If none of the schedules work for you, you could learn the same stuff through a series of private lessons.

No matter how you study and practice with me, I’ll help you be a better photographer.
 

About Sam

Sam D'Amico, a professional photographer and photography instructor, helps anyone who wants to be a better photographer. 

He'll work with his students to increase their understanding of camera operation, composition, light, and lighting. 

Sam started working as a professional photographer in the mid-1980s.

Most notably, from 1992 to 1997, while working as a freelance photographer, he photographed over 500 assignments for the New York Times.

Additionally, Sam received awards for his work while exhibiting his photographs in shows. 

Sam began teaching photography professionally in 1998 through the Highland Park, N.J. recreation department. 

In 2002 Sam moved to Washington, D.C., and began teaching at the accredited Washington School of Photography in Bethesda, Md.

It was in 2003 that Sam developed his curriculum and started teaching classes in Washington, D.C. 

In 2018 and 2022, the Sam D'Amico Photography Classes were voted the "Best of DC" art class by the readers of the Washington City Paper. 

Many photography teachers spend a lot of time teaching about DSLRs and rules of composition that create homogenized, rigid photographs.

On the other hand, Sam teaches about camera operation, thought process, and the individual photographer's visual communication intent. 

This approach to teaching allows his students to use ANY camera (yes, even the camera on their phone) and break free of the rules of composition.

Approaching the creative process this way allows for fluid and spontaneous photographs unique to the photographer creating them.

Sam encourages his students to find their ways as photographers. 

He instills the skills in his students that result in creative, engaging, and unique compositions that reflect the photographer's intended one-of-a-kind visual expression.