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Aperture ~ Shutter Speed ~ ISO ~ The Holy Trinity of Photography

artist6 months ago12 min read

Putting You In The Driver's Seat



The Human Eye ~ The Most Advanced Camera

Today I wanted to begin a short, but potent series on understanding photography.

If you are trying to make a serious attempt at improving your personal stills photography or motion picture skill, fully absorbing the material in this one article will get you a long way towards your goal.

Please feel free to interact with me on the You Got Snekked Discord Server

Home of The Artist Project

Understanding the camera first, is more important than photography itself, in my opinion.


Understanding the core functions of the camera itself is the key, foundational bedrock to help photographers be as independent as possible as quickly as possible.

I believe in an uncluttered mind when it comes to a human interacting with a camera.

If you understand what the major parts of the camera do, you will be free to explore the possibilities of your own imagination, and apply the very specific understanding you have gained to explaining in great detail to the camera what you want in a particular shot. The camera can only do what it is asked to do. Even if you set it to fully automatic. You asked for it.

Any person or animal can be trained to perform specific tasks. Using presets that others have created can be a helpful tool to get a beginner started. That said, even the most basic understanding of the major functions of the camera will set you free to create at will, and set you up for personal success and complete independence.

Many high level photographers often make a large part of their living from instructional material. These books and courses, without exception, are not necessary but merely optional, in my opinion.

Why would I make such a statement? Clearly there is a lot to be gained from other photographers. I happen to own many terrific photography books. One of them being by Joe McNally who I have followed for many years. He is creative and knowledgeable and can apply his knowledge to any camera he picks up. If the camera is too basic it will not give him the control he needs over the shot.

None of the books in print are more valuable than your own basic understanding of the camera's major and minor functions, and the ability to apply them to your own style.

Lemme Splain

With this post, it is my goal to unravel the mystery of the camera.

I will be doing this by relating the camera & lens to the human eye.

The main functions of the human eye and the modern day camera have many correlations.

The camera and eye have a lens,
an electronic and organic nervous system,
image sensor or retina,
an aperture or pupil and iris
a shutter or eye blink,
an optic nerve and brain for image processing and storage
and in the camera, an information gathering center that reads the information off of the image sensor and stores it in memory.

These similarities are not only undeniable, but they make perfect sense, because the camera in use, is simply an extension of the human eye and gives the ability to create, store and share what you and the camera saw together. In the end, the camera is your companion to share your experiences if you choose to make it so.

The difference between a camera and a healthy human eye, is that the functions of the human eye are automated and hard wired to the optic nerve and brain.

In many ways a camera has more technical ability that the human eye, yet it remains that the camera needs to be told exactly what to do. Of course, Auto functions have gotten much better over the years and you can now choose Scenes for particular situations like night photography, landscape, portrait and more.

What remains is a fundamental flaw in failing to understand the major functions of the camera’s photographic process, and a massive gap between the amateur’s and professional’s knowledge and results.

Today we are going to narrow the gap between amateur and professional photographers by a wide margin.

The Human Eye & The Modern Camera

Every modern camera, consumer, prosumer and professional have a core number of things in common. What can be difficult and confusing is that camera manufacturers have their own systems of accomplishing these core settings either by electronic menus, external buttons that can be dedicated or programmed, or a combination of both.

Here are the core settings we will be discussing. In the future we can discuss secondary settings that are not as vital as the core settings yet do add a lot to the photography tool kit of each individual.

The Holy Trinity of Photography

Aperture or fStop
Shutter Speed

The majority of easily findable information will tell you that the three most important camera settings are Aperture, Shutter Speed and ISO.

Without the inclusion of Shutter Speed or fStop, there is no discussion about moving forward in a meaningful way with achieving more skilled photography results. So let’s start there and take them one by one.

Aperture or fStop


The Aperture of a camera’s lens is equivalent to the human eye’s pupil and iris. They both, very simply, control the amount of light that can enter either the camera or the eye.

Every single camera that is worth shooting with will give you control over the aperture.

For example, let’s say that you have a very good quality camera lens and its fStop capability is f2.8 to f22

Very simply, the blades of the lens that form the equivalent of an eye’s iris, can open up to f2.8 to allow an incredible amount of light to be gathered by the lens. This is the exact same principle as the human eye’s iris opening fully in the dark to try to gather as much light as possible to see. This is also why the camera and the human eye can be blinded by a light source when the aperture/iris is wide open. For the camera, this would result in a photo that is referred to as having ‘blown out highlights’ or just completely blown out and unusable, and the human eye will be blinded if a bright light source is introduced when the iris or aperture is wide open.

It really is as simple as that. Everything to do with the technical achievement of a wonderfully blurred, out of focus background or foreground or both can all be achieved by fully understanding how your eye and the camera’s aperture work.

If you want a practical way to start to understand how aperture works as far as blurring effects go simply try this:

Close one eye and hold up your thumb about 30 cm or a foot from your open eye. Focus on your thumbnail and and try to bring everything in the background into focus while staring at your thumb nail and keeping the nail in focus. Simply, you can’t. Similarly, do the exact same thing but now stare at the background, and while keeping the background in focus, try to bring your thumbnail into focus. Again, not possible. This will start to give you an understanding and appreciation for what your camera sees.

If you dial a camera lens’ Aperture all the way to nearly closed at f22, nearly everything will be in focus in the foreground and background.

Kermit1.1 (2).jpg

Image TheBugIQ

However, if you dial it way open to f2.8 you will have a very ‘narrow focus plane’ and things in front of and behind your focus point will be out of focus. This can create a lovely and desirable effect.

Image TheBugIQ

Now here’s the thing. No one part of a camera or eye rules. It all matters.

Shutter Speed ~ The Organic Eye’s Blink


In the same way a human eye blinks, so it is with the camera’s shutter. There are, of course, vast differences between the two, but that absolute reality that they both ‘blink’ is absolutely similar. A camera can ‘blink’ much faster than the human eye with a mechanical or even electronic shutter. The fact remains at this point that the human eye is a lot more akin to a movie camera in many ways than a still frame camera.

As an experiment to make my point easier to understand, simply stare at a single point across a road and blink as fast as you can as a car goes past. This will give you the sensation that the camera ‘feels’ or sees when it is taking a still shot, or the frames of a movie camera as it is recording.

If you attempt to look at a light source that is too brilliant like the sun, you will reactively find yourself blinking rapidly. Or at night if someone shines a bright flashlight at you, you will either squint and/or blink rapidly. You will also attempt to shield your eyes to reduce the direct impact of the light, but we’ll talk about that a bit more separately.

Shutter Speed works in conjunction with Aperture to control how much light enters the camera by controlling how fast the shutter ‘blinks’ or cycles along with the size of the ‘iris’ that determines how much light can enter.

Some common shutter speeds for everyday outdoor photography on a sunny day at the park would range roughly from 125/s to 1000/s with 250/s and 500/s also being pretty common.

The faster the Shutter Speed, the greater the ability of the camera to stop or freeze motion.

Tip: The mastery of Aperture and Shutter Speed, in particular, give you the ability to be individually creative and expressive with actions such as dragging the shutter and/or introducing a light source like a flash to produce a combination of effects like the trailing, blurred body of a leaping ballerina and freezing her motion at the apex of her jump. These effects are achievable for everyone with basic gear and solid knowledge.

This tag team between Aperture and Shutter Speed is a powerful combination, and gets us light years ahead in our control over the camera. Pun more or less intended.

ISO, the Human Eye’s Retina

The final part of the camera’s Trinity is ISO. ISO, in case you can’t fstop yourself from wondering, simply stands for International Standards Organisation.

Nobody cares. It just means a measurement used to determine light sensitivity of standard emulsive camera film. Back in the day in my 35mm camera, I was typically running 200 or 400 ISO film. If I was outdoors at a fun BBQ event in a park with friends, I might use 400 or 800 on a super sunny day.

Essentially, ISO would be similar to your retina, and the Aperture and Shutter Speed control the amount and type of light information reaching the retina.


Think of it like being in a huge dark cave that you can literally see nothing in, and then in the distance someone lets in the sun by moving some rocks or opening a door. The bigger the opening, the more sunlight will flood into the cave. Your retina would be incredibly sensitive after being in the dark.


Similarly people can experience snow blindness from UV rays and you have no doubt seen the eye bands with tiny slits for the eyes to reduce the sun’s light being reflected off the snow.

ISO is really as simple as that. Light sensitivity.

ISO 100 or 200 film is much less sensitive to light than 1000 or 1600 ISO film.

ISO 1600 film is so sensitive to light that it would have been the type of film used for night photography such as surveillance or street photography. It never had the fine detail and lovely film grain of film like ISO 100 which would be used for more controlled conditions like studio portraits where you can control all of the environmental variables like light source and direction.

The magic of the modern day camera is that I am carrying around an ocean tanker full of film now on demand. When I put a roll of ISO 400 film in my 35mm camera, that was all I was shooting until it was finished. With modern day cameras you can change ‘film’ from shot to shot by simply changing the ISO to any desired number.

This flexibility is something we have come to expect and depend on and could never dream of returning to the dark room era. There was a half million dollar dark room studio for sale near me last year for $3000. If that’s any indication. No one is going back there unless they just can’t help themselves from being that retro. I’m cool with that.

Please ask any questions in the comments below and I will be happy to answer. If you have a specific problem you are trying to solve please ask away and give a photo example or Instagram link.

Aperture ~ Shutter Speed ~ ISO nail those down in your mind, do the few little eye experiments I suggested or make up your own and we’ll tackle the other Holy Trinity of Photography next time.

Happy Snappin’


While @TheBugIQ is a full time musician, he was also a full time, paid photographer for more than five years while living in British Columbia, Canada.

Images CC0 and ©TheBugIQ

NB I interchangeably use the Iris and Pupil parts of the eye in this article to compare a camera's aperture, as the iris and pupil work in conjunction to accomplish the same function as the aperture blades of a lens in order to allow more or less light in.

©This article in its entirety is an original work from @TheBugIQ Please ask permission if you would like to quote or use any part of it.

©The photgraphy™ tag is exclusive to TheBugIQ and may not be used without permission. It saves me time when I type it. :grin: :joy:


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