Dad’s Photo Lessons Part 2 – Understanding Exposure

Thank you to everyone who read Dad’s Photo Lessons Part 1 last week.  Truth be told, what I would love to do is teach a photography class, but I just don’t know where I would possibly fit it into my crazy life.  I enjoy writing these posts as I’m still teaching, but I get to do it from the comfort of my home.

This week I’m covering exposure.  This was a lesson I learned when I was about 13.  Think back to when you were 13.  I can’t speak for any of you but I know I was impatient and just wanted to take pictures not learn about f-stops and corresponding shutters speeds.  Some how my dad found a way so that it would make sense to me.  In recent years I’ve read a number of books and articles on the subject and I have to admit no one has ever explained it as well as my dad.

Understanding Exposure – Dad’s Way

Exposure can be broken down into three elements: ISO, shutter speed and aperture.  The three settings on your camera allow you to “play with the light” that enters your camera.  There are many metaphors out there to help you understand these terms, but this is how I remember my dad explaining it.

ISO = Light Sensitivity

ISO is light sensitivity.  Dad’s explanation – ISO is like a pair of sunglasses.

We wear sunglasses on a sunny day so our eyes are less sensitive to the light.  We wouldn’t wear sunglasses indoors because everything would be too dark due to the lack of light entering our eyes.

In the old days of film, ISO (International Standards Organisation) was how sensitive the film was to light.  Now it relates to how sensitive the image sensor of your camera is to light.  The higher the number the more sensitive the ‘film’ is (imagine your sensor with regular glasses on).  Now a low ISO number essentially means that your sensor is wearing sunglasses.   Therefore, on a sunny day you can shoot at a low ISO, but you need to shoot at a higher ISO when  there is less and less light.

iso visual

Now the trouble is, the higher your ISO the more noise (grain) your photo will have.  Most higher end DSLR have the capabilities to shoot in low light.  It is important to experiment and find your camera’s ISO limit.  Personally I know that on my D80 I don’t want to push the ISO past 800 because the photos are quite grainy.

grainy photo

no grain

SHUTTER SPEED = Exposure Time

Shutter Speed is how long the shutter is open to light.  Dad’s explanation – Shutter Speed is like blinking

When you step out into the bright sunlight (with no sunglasses) you generally blink your eyes  rapidly to  allow them to adjust to the bright light.  When you step into a dark room we often widen our eyes and try to blink less.  This is to allow more light to enter our eyes.

shutter visual

The longer your image sensor (film) is exposed to light (slow shutter speed) the more light the image sensor (film)  is exposed to.  This means you will have a brighter photo.  Be careful though, the longer your shutter speed the greater chance you have of capturing motion blur.

APERTURE = Size of lens opening

Aperture is the size of the opening the light passes through.  Dad’s explanation – Aperture is like your pupil

If you have every had those dilation drops at the optometrist you know exactly what I mean.  They put those drops in, your pupils dilate wide open and you need to wear your sunglasses because everything is so bright.  Now think about no drops in your eyes.  You step out into the sun and your pupil contract down into little pin points.  conversely you step into a dark room  and your can almost feel your pupils try to widen as far as possible to let in the most light.

Aperture visual

The larger the opening – the more light.  To create a larger opening you have to set your camera to a smaller f-stop setting, as this is an inverse relationship.  Big f-Stop = small opening and small f-stop = big opening.  I don’t know why they have to invert it; it just makes it confusing.  So I remember it this way.  BIG LIGHT SOURCE = BIG f-STOP and SMALL LIGHT SOURCE = SMALL f-STOP.

Now the second thing you need to remember is that the smaller the f-stop the smaller the depth of field (DOF)  is.  So we can add another component to remember.  BIG f-STOP = BIG (WIDE) FOCUS AREA (DOF) and SMALL f-STOP = SMALL (NARROW) FOCUS AREA (DOF).  Ever wondered how photographers make the background blurry?   They use a smaller aperture to create a narrower focal area.  This creates what is known as BOKEH.  By doing this, the subject is in focus, but the background is blurry.

AN EXAMPLE: Here is an example of shifting shutter and aperture together.  Rarely do I move just the shutter or aperture; I usually adjust them simultaneously.  In this case the first image was far too dark.  I lowered the shutter speed as far as I felt comfortable (1/40 sec).  Any lower than that and I have to worry about hand blur as I wasn’t using a tripod.  Knowing I needed to still allow for greater exposure I increased the aperture.


Get Playing With Exposure!

The beauty of these three settings is that you can adjust them to allow you to take photos in a variety of lighting situations.

Now I’m a big advocate for hands on learning and there are two ways you can do this.

1. Check out the SLR Camera Simulator at Camera Sim.  This online simulator will allow you to try your hand at adjusting camera settings without even leaving the comfort of your own chair.  After some playing around you will  have a better understanding of how these three settings are interrelated.

2. Go old school.  Grab your camera and take some photos.  The old school way is how I learned.  I remember my dad sending me out into the yard with the Nikon and a notebook.  His instructions were simple:

  1. Find a subject to photograph
  2. Record your camera settings (ISO, Aperture and Shutter)
  3. Take a photo
  4. Change only one setting (I always start with shutter speed) Don’t forget to record the change you made
  5. Take another photo
  6. Change that setting again (Don’t change to aperture.  If you start with shutter speed, you need to stay there)
  7. Continue and then look at your photos.  Pay careful attention to how just that setting changes the quality of your exposure.
  8. Go back to your original settings and change a different setting and repeat the process.

Old school is time-consuming, but if you want to gain a greater understanding of how your camera handles light this is the best way to learn.  When I had committed to learning my camera inside and out, that is exactly how I did it.

Turn That Dial!

The important thing to remember is that you can’t adjust these settings if you are shooting in AUTO.   So hopefully you read your manual after last week’s lesson and you understand the different shooting modes of your camera.  I’m not going to go into all of them, but here are the ones that most photographers will use.

AUTO – Your camera makes ALL the decisions for you.  This works well when you need to snap a fast pic and don’t have time to worry about settings.

PROGRAMMED AUTO (P) – Your camera will decide on the shutter speed and aperture, but you have the ability to over ride these settings.

APERTURE PRIORITY (A) – This allows you to make decisions about the ISO and the aperture.  Your camera will then adjust the shutter speed for you.  This is good for when you want to have control over the FOCUS  AREA (DOF) to create bokeh

SHUTTER PRIORITY (S) – You guessed it…this allows you to make the decisions about the ISO and shutter speed.  This is excellent for when you want to freeze the action ( fast shutter) or blur the action (slow shutter).  The camera will choose the appropriate aperture for your photo.

MANUAL (M) – You are in complete control and make ALL the decisions!  This gives you maximum control over exposure!

Lesson Summary:

Low ISO = Less Light Sensitivity (Good for bright light) , High ISO = High Light Sensitivity (Good for low light)

Fast Shutter Speed = Less light entering the lens (Good for freezing the action) , Slow Shutter Speed = More light entering the lens (Good for creating motion blur)

Big Light Source = Small Aperture (Good for full crisp images), Small Light Source = Big Aperture (Good for bokeh)

cheat sheet

Dad’s Advice = Practice Changing Your Settings

Next Week’s Lesson – Holding Your Camera Properly (DSLR, Point & Shoot AND Phone)


10 thoughts on “Dad’s Photo Lessons Part 2 – Understanding Exposure

  1. Good job with this. When I first started making pictures more seriously, everything was manual so your information was drummed into our heads simply by the act of doing it. Now, with all the bells and whistles, many people either don’t understand exposure as it relates to ISO, shutter speed and aperture or don’t practice enough.

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