This month’s tutorial is a fairly simple concept to grasp, but its’ application can be difficult to use if you don’t understand the correlation between shutter speed and aperture. I discussed this correlation in the Spring 2008 issue of Canadian Scrapbooker, and again back in October, in Part II of that month’s tutorial.  However, since it’s so important in understanding photography, we will delve into it again a bit later on.

First, however, let’s look at the Sunny f/16 rule.  This guideline in photography was developed as a rule of thumb to achieve correct exposures without a light meter, while outside or in direct sunlight.  It states that “on a sunny day, set aperture to f/16 and shutter speed to the [reciprocal of the] ISO film speed.” (reference:  www.wikipedia.com).  So what does it mean?

Well, if you are shooting at an ISO of 100, the reciprocal of the ISO film speed would be 1/100, or the closest available shutter speed*  of 1/125 (*Note: many digital cameras deal in 1/3 increment values for shutter speed, but for this tutorial, I will deal with whole values only.  Thus 1/125 is the closest available shutter speed when considering this).   Therefore, the Sunny f/16 rule means that you can usually assume, when shooting with a film speed or digital ISO of 100, that an aperture of f/16 and shutter speed of 1/125 will give you the proper exposure on a sunny day.  This is also true for any equivalent setting.  This is where the understanding of the correlation between shutter speed and aperture kicks in!

To review:  Imagine that you have your kitchen faucet’s tap wide open, filling your sink to do a mountain of dishes.  At this speed, let’s say it takes a couple of  minutes to fill your sink with hot, sudsy water.  Now imagine that the tap is barely open, so that water is just trickling out.  It would take much, much longer to fill, right?  Aperture and shutter speed work the same way.  For example, per the Sunny f/16 rule, the following is a proper setting on a sunny day:

ISO 100 > f/16 > 1/125*

Now, as I described in the Spring 2008 issue, the following settings would be equivalent to f/16, 1/125 sec.,  at ISO 100:

f/22 > 1/60
f/11 > 1/250
f/8 > 1/500
f/5.6 > 1/1000
f/4 > 1/2000
f/2.8 > 1/4000

But what if I want to shoot our subject with a very short depth of field, as in our January assignment?  As per the above table, you would set your aperture to f/2 and your shutter speed to 1/4000, which is a very fast shutter speed.  You can also achieve the same exposure by changing your ISO, as we discussed in the October tutorial.  By using a less sensitive ISO speed, you can use a slower shutter speed.  Check your camera’s manual to see your minimum ISO speed.

Taken with Nikon D70 at f/16, 1/400 sec., ISO 400

But what if it’s not sunny?  Well, the following adjustments can be made to your aperture for variable lighting situations:

Sunny > use f/16
Slightly overcast > use f/11
Overcast > use f/8
Heavily Overcast > f/5.6
Dawn/Dusk > f/4

(Because of the reflective nature of sand or snow, you should DECREASE your aperture when following this rule to f/22)

The Sunny F/16 rule, like everything is not fool proof.  You may need to adjust your aperture a half-stop or more, if your subject is backlit.  It is best to use bracketing (see October tutorial: Part I) to ensure that you capture to best exposure.  Consider this example:

Taken with Nikon D70 at f/8, 1/250 sec., ISO 100

When applied to this setting, the Sunny f/16 rule dictates that the optimum exposure should be f/16 > 1/125th sec., or the equivalent of f/11 > 1/250th sec.  However, in noticing that my daughter’s hat cast a slight shadow on her face, I decided to open up my aperture one more full stop to f/8.  While there is still a slight shadow, her features are visible and her skin tone is not overexposed.

Alright – are you ready to play along?  The trick will be to find a sunny day in the middle of winter – but you can use the chart of equivalents above for overcast situations!  If you have any question, please leave me a comment on this post or email me! 

Your February assignment:

Using this tutorial as a guide, apply the Sunny f/16 rule to determine the proper exposure for your outdoor photo.  Please remember to include your camera settings to be eligible for the draw!

Deadline: 11:59 pm EST, February 28th, 2010

Please submit your photo(s), using our submission form, for a chance to be entered into our draw. A randomly chosen entry will be drawn after the deadline. Please click HERE to review the rules regarding this draw before submitting. Please note – submissions that are not relative to the tutorial and/or do not abide by these rules will NOT be posted on the blog, or entered into the drawing.

Our February prize pack will be revealed shortly!

Happy Clicking!