Or
The Exposure Triangle


Aperture

Size of the hole that lets light into the camera
 Shutter Speed

How long the light is allowed to enter the camera
 ISO

How sensitive the media recording the image is to light

The “hole” story


The aperture is the hole that allows light to travel through the lens of the camera.

Likely one of the most quoted, and least understood photographic term.
 “What was your aperture setting?”

F 16
 ”Looks really good”

Generally speaking, people ask about aperture settings, however they don’t ask about the ISO setting or shutter speed.


A normal issue people have when discussing aperture is that a large number results in a small hole….how?

The aperture value, often referred to as an F-Stop comes from a mathematical equation.

Focal Length of lens / Physical size of opening

100 mm lens/ 25mm opening= F4
 100 mm Lens/ 10mm opening= F10
 You will get a bigger number with a smaller hole and a smaller number with a bigger hole due to the math of division.


Another thing that messes people up is how is F5.6 to
F6.3 twice the light?
 Again, this is a math thing….derived by focal length of lens, physical size of the opening and the good old (pi)r2

A larger aperture allows more light to enter the camera in less time, this normally equates to a faster shutter speed.
Conversely, a smaller aperture will normally make for a slower shutter speed.

One of the biggest things you need to know about aperture to get started in photography is this:
 It controls depth of field


How much of your image do you want in focus?

Just the persons face, I want the background blurry
 Small F-Number, (i.e.: F5.6), this will keep the subject sharp while blurring the background.
 Everything…I want it all
 F16 to F22 are good numbers for keeping the entire image in focus.
 For example…

Settings for this shot were:
ISO: 100
Aperture: F6.3
Shutter Speed: 1/320 th of a sec
Focal Length: 163mm

Settings for this shot were:
ISO: 100
Aperture: F22
Shutter Speed: 1/13 th of a sec
Focal Length: 28mm


Depth of Field is a term put to the amount of image that is in acceptable focus.

There is lots of tecnobabble on this subject, however suffice to say that the following rule of thumb applies to your focal point:
 Two thirds behind
 One third in front

Focal Length (mm)
10
20
50
100
200
400
Focal Distance
0.5 (1.64 ft)
1.0 (3.281 ft)
2.5 (8.202 ft)
5.0 (16.4 ft)
10 (32.8 ft)
20 (65.62 ft)
Based on an aperture of F4
Depth of Field
0.482 (1.581 ft)
0.421 (1.381 ft)
0.406 (1.332 ft)
0.404 (1.325 ft)
0.404 (1.325 ft)
0.404 (1.325 ft)

Aperture value F22
This small aperture opening forces the shutter to stay open for a longer period of time, this allows you to make water seem silky.
Smaller apertures normally require a tripod
Almost everything in the image is in the same focus as a small aperture allows for greater depth of field.

Aperture Value F5.6
The large aperture opening allows a great deal of light into the camera in a very short period of time, as such, the shutter speed will be increased significantly.
Backgrounds are normally blurred with large apertures as the shutter isn’t open long enough to capture all of the reflected light and detail
Large apertures can be used easily for hand held shots

Aperture value F8
Mid-range apertures will allow you to have greater depth of field while still blurring some of the background.
This can be useful when you are trying to capture larger groups of people, or there are subjects of interest in the general proximity of your main subject.

I chose F13 for the relatively deep depth of field, however I didn’t want the shutter open so long as to make the waves in the background blur.
Good texture in the foreground and lighthouse in acceptable focus in the background gives the person viewing the image a sense of the location and time of year.
Darker lighting and dark clouds set the mood.

Applied a shallow depth of field on this shot to isolate my primary subject.
I wanted to show the male to be ever vigilant while the female was feeding.
Female and background are blurred, foreground is limited in focus.
Male in sharp focus with light reflection in his eye.

Questions?