In a couple of weeks, I'm giving a talk to my church photography group on "The Basics of Exposure". I'm trying to educate people on the very simplest principles of exposure. After the talk, we'll have tome time for some practice / exercises.

The audience are people who are only just starting out in photography.
My aim it to help my audience get over the initial confusion which many people encounter when they come up against all these mysterious numbers "1/250", "f/2.8", and so on.

Any ideas for how to teach this? Any suggestions for examples or exercises?
Anything I should avoid?

Thanks for any help!

  • 2
    Just don't say "exposure triangle". :)
    – mattdm
    Jan 21, 2011 at 20:52
  • 1
    @mattdm I was so waiting for that comment...
    – rfusca
    Jan 21, 2011 at 21:24
  • 1
    Explains exactly why changing a setting results in an outcome. For example, why exactly does a large aperture create a small depth of field etc. Jan 22, 2011 at 3:41

5 Answers 5


I've taught a similar class at my church with a curricula built on the premise that light is like water; the longer you leave the valve open, the more water you get. Ideally, you want a glass that, when full, represents the perfect exposure. A smaller glass would be the equivalent of a higher 'film speed' and takes less water to fill.

Indeed there are a few other factors that the water analogy helps illustrate. An incandescent bulb is like an eyedropper filling the glass. The sun, a fire hose. Aperture governs how much water the user lest through. The shutter is how long it's open...

You get the idea.

It makes a great visual point when you have a person with a pitcher filling a small glass while another students attempts to fill a container with an eyedropper. Makes the dry stuff more fun. No pun intended.

  • Shutter = tap open time, aperture = pipe size, ISO = pressure? Jan 21, 2011 at 23:31
  • Better yet, ISO = size of the glass. Jan 21, 2011 at 23:31
  • 1
    Indeed, ISO = Size of the glass. Pressure would be the amount of available light. Sun = Fire engine with 2500GPM pump; Candle = water pressure in the shower from my gravity-fed springhouse while my son washed dishes in the kitchen.
    – Ofeargall
    Jan 22, 2011 at 0:17
  • @Craig, thanks for the +1. I have a lot of fun using this while teaching. Makes it simple.
    – Ofeargall
    Jan 22, 2011 at 0:36
  • Great analogy..
    – labnut
    Jan 22, 2011 at 7:48

I'm someone that just started learning all this stuff, and I've even tried to explain things that I have learned to some of my friends. Here are some points I would make:

  • Pictures, pictures, pictures! Show some example shots to illustrate what you are talking about. This is what Bryan Peterson does in Understanding Exposure and why I like it so much. Things you should definitely show:
    • The same exposure with different apertures and shutter speeds
    • under and over exposed shots
    • Using the shutter speed to stop motion or let it blur
    • Using the aperture to take portraits and landscapes At the end you want them to be able to look at two pictures and be able to articulate what settings probably changed to get the desired effect. When I started out I would look at pictures online and try to predict the exif data. Interact with them and let them try to guess.
  • Use the human eye as an analogy. (This is how I have thought of it -- some people may like this better than the water analogy).
    • The aperture is just like a pupil that you manually open and close more. When your pupil is open more, more light comes in.
    • The eye lid similar to the shutter. Imagine a closed eye, and depending on how fast the eye opens (and closes again) and how big the pupil is, a certain amount of light will get in.
    • ISO is a little tough to use in the eye (or water) analogy. But I find it is simple enough to explain it as something separate. The reason is that the other factors effect the amount of light that enters the object (eye or camera). The ISO will tell you how a given amount of light effects the film/sensor. Lower ISO means you are more resistent to light so you need to hit it with more light to get the same effect as something with higher ISO. You can probably relate this to the retina and say that ISO changes how your retina and brain perceive the amount of light that enters the eye.

I hope this helps. Good luck!

  • It'd be awesome if we could get someone with Actual Science to further explain, but as I understand it, a protein called rhodopsin is required for the low-light rod cells in the retina to function. This protein is broken down by light, which effectively lowers "ISO". When it's dark, the rhodopsin replenishes, raising sensitivity (with the tradeoff of poorer color response and less sharpness).
    – mattdm
    Jan 23, 2011 at 5:12
  • But really, the eye isn't quite an analogy, because it's basically an example of the thing you're already explaining, except incredibly complicated. :)
    – mattdm
    Jan 23, 2011 at 5:13
  • @mattdm: ha, ok. I still find the eye example to be helpful. I totally made it up when I was learning about exposure. When I've tried to explain aperture to people, I can see the light bulb go off in their mind when I relate it to a pupil. ::shrugs::.
    – Tom
    Jan 23, 2011 at 5:24
  • I'm not saying it's completely bad to use. I'm just sayin' the pupil is an aperture (and the iris, the aperture stop). So that part is explained really well by looking at the eye. When it comes time to talk about the rest of the system, though, probably time to move on.
    – mattdm
    Jan 23, 2011 at 14:25
  • 1
    I hadn't thought of the eye analogy, but no that you mention it, I can see that it might well be helpful for some people. Many thanks, @Tom.
    – AJ Finch
    Jan 24, 2011 at 9:56

If the are going to have their cameras with them, you can just tell them to set the to manual mode, let them take pictures at various settings and look how it effects the outcome.

For example, you can start with 1/50 sec, f/5.6 and ISO 400 (or whatever is the proper exposure at the spot), then stopping down to f/11 and seeing what does that do, then raising ISO to 1600 and comparing the results, then playing with exposure time, etc. I belive you can illustrate what each of these settings do and how do they relate.

After that you can show them how to fix some of these setting using semi-auto modes.

If you have some kind of projection screen, you can show photos takes with these setting live from your camera. Or you can do this without any cameras and just show examples of the results. But that will be less fun.

  • excellent ideas for exercises. I'll use some of that. thanks!
    – AJ Finch
    Jan 22, 2011 at 15:17

When CreativeLive started out I started to take a look at the http://creativelive.com/courses/digitalphotography Fundamentals of Digital Photography with John Greengo!

I knew a lot about photography at that moment, but the way he explains it makes you rethink all you know :)

Maybe you will find some free clips on the internet with John Greengo

The way he explained shutter speed and aperture Take a picture of a water stream at different shutter speeds and show that to your audience, do the same for aperture with the dof.

  • Best course on the basics of photography ever!
    – ysap
    May 26, 2011 at 1:54

This website should help explain the basics about exposure. http://photo.comm.psu.edu/

  • 2
    Hi JHB welcome to the site. The resource that you link to is surely of interest but could you please "sum up" the most relevant content, so that if the link ever changes you answer remain useful?
    – Francesco
    Sep 23, 2012 at 22:35

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