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Chapter Nine

Apertures

(It will help to have your camera and a normal lens available while reviewing this lesson.)

Understanding Apertures and the subsequent chapter on Shutterspeeds involves an understanding of math, non-lin

numerical values, and terminologies not always associated with the general understanding of taking pictures with automa

exposure cameras. If your camera does not offer this controllability or you simply do not want to use this controllabi

of apertures and shutter speeds you should skip Chapters Nine (this chapter) and Eleven. Chapters Ten and Twelve d

with Depth of Field and Action Photography respectively and should give you some insight to the control you have o

creativity in your pictures as they pertain to the automatic and program modes your particular camera may possess.

will try to be gentle; you will probably not need paper and pencil.

Apertures are generally considered to control the creative component of your photographic artistic self, while

apertures compliment, the shutter speed, is considered to be the action, or sports, component. The two work together

a proper exposure. We will talk about apertures first.

The different apertures you see in the illustration on the next page control the quantity (the amount) of light allowed

pass through your lens to expose your film, and NOT the amount of detail in the scene. If you want to get technical, top left lens opening, f/2.0 (pronounced f 2 point oh) passes 128x (times) as much light as the bottom right aperture, f

(pronounced f 22). The f/ in the aperture designations stands for fraction and should be generally related as such

reference to the numerical value of the apertures opening. In plain language, and in a non-linear sense, f/2 can be loos

described as and f/22 can be loosely described as 1/22nd. Although the exact fractional representations should not

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We refer to aperture size relationships in many different ways. They can be called f/stops, apertures, stops, openings, l

openings, Waterhouse stops, plus many others. They all mean the same thing: How much light is going to be applied

your film when you take the picture. We will be using terms like open upandstop downto reference using a larger

smaller, respectively, aperture for a given scene. Keep in mind that each change in aperture size, i.e. a change from f/22

f/16, either lets in twice as much light (by opening up by one EV) or reduces the amount of light passed to the film by

(by stopping down one EV), i.e. f/2.0 to f/2.8.

To further exemplify this effect, a change from f/22 to f/11 (opening up by two EVs) allows 4x more light for exposing y

film, while stopping down your lens from f/2.0 to f.4.0 reduces the amount of light reaching your film by 4x. The sequen

of change, per stop, is 2x-4x-8x-16x-32x-64x-128x, etc. Each full change in exposure either cuts the amount of light gett

to your film by one-half or allows twice as much light to get to your film depending on whether you are opening or clos

the aperture setting.

You will want to know which aperture to choose, or be aware of the aperture your camera has automatically chosen, baon the reflected brightness of your scene. As a general rule, for both manual cameras and most automatic ones, y

cameras light meter will choose, or indicate a change to, an appropriate shutter speed (Chapter Eleven) for the apert

you have selected. As we said before, the aperture AND the shutter speed work together to create a proper exposure

small chart will help you understand the relationships of the different aperture sizes and their possible uses. Similar cha

appear inside some photographic manufacturers film canisters or wrappers:

If you are in this situation: Aperture Shutter Speed

Sunlit Sand or Snow f/22 1/ISOBright Sunlight with dark, crisp shadows f/16 1/ISO

Hazy Bright Sunlight with dark, soft shadows f/11 1/ISO

Cloudy Bright, like you're inside a ping-pong ball f/8 1/ISO

Cloudy Dull with no apparent shadows f/5.6 1/ISO

Stormy Dark with impending rain or storm clouds f/4 1/ISO

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As we explained before,ISOdenotes your films sensitivity to light with a number reference such as ISO 64 or ISO 400.

placing a 1/ over the ISO number (1/ISO) we are designating a fractional shutter speed setting to use, i.e., 1/64 seco

(We really mean 1/60, as there is no 1/64 setting on your cameras shutterspeed dial.)

You can see from the above chart that as the lighting conditions of your scene deteriorate (get dimmer) you must us

larger lens opening to compensate for your film speed (ISO). Your film speed is the one variable in your expos

computation you cannot change very easily without changing rolls of film or entire camera systems.

Also, in the above chart you would set your shutter speed to the reciprocal (inverse) of your film speed, i.e. if your film

ISO is 100 you would select the closest shutter speed setting your camera has to this 100 number; this would be 125 (

or 1/60 second, could also be selected, but 125 is recommended when using this particular chart). Leaving your shu

speed set to 125 (1/125th of a second) you could take a good exposure of any of the scenes in the above chart

changing only the recommended lens aperture. This takes the guesswork out of making a good exposure and is v

useful information for those of you using fully manual cameras or cameras that can function with dead batteries or batteries at all.

The green 'A' in the example to the left is an exposure setting called Aperture Priority.

Basically, the Aperture Priority Mode makes the camera automatically select an appropri

shutterspeed for the aperture you have manually decided to select. The Aperture Prior

Mode position is included on the Shutter Speed Dial to prevent you from mistakenly trying

choose a shutter speed when you really want the camera to make the selection for you.

careful to not select too large an aperture as you might run out of fast shutter speeds to ma

up for a good exposure with the aperture you have chosen; your camera should tell you wh

this is happening by giving you some kind of error indication within the viewfinder. Y

owners manual should describe this warning feature if it is present on your camera.

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Those of you with semi-automatic or automatic cameras might

notice your camera recommending different aperture and shutter

speed combinations in the scenes depicted by the aforementioned

chart. You will want to override your cameras recommendations

and USE THE CHART if you want your pictures to turn out

correctly exposed. Learning how your camera measures and sets

itself in relation to the above chart will tell you how it will respondto difficult lighting situations. Keep notes and learn! Most of the

time your camera will correctly measure the amount of light in

your scene. But, if you catch your camera in an obvious contest

with The Chart you should reconsider whether to use your cameras

recommendations or those of The Chart.

Many camera exposure meters cannot accurately meter somescenes and will produce results different from those you had

planned. If your instruction manual says your camera has special

metering modes to compensate for these special lighting

conditions, follow those directions and recommendations closely,

then check the results by critiquing your bracketed pictorial results

(your pictures).

We always use The Chart for lighting verification.