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Photography exposure tutorial for beginners - shutter and aperture

Sunday, June 19, 2011
Photography is about painting with light onto a recording mechanism. Exposure is a simple camera technique which can be difficult for beginners to initially grasp.

At one time light was captured by a camera and exposed onto chemicals. Today we have electronic sensors which filter the light and let a powerful computer translate the information into binary code. We have changed what records the light but the system of controlling the exposure is the same as it was since the beginning. A photographer manages the amount of light by controlling the lens aperture, the camera shutter speed and the sensitivity of the recording material. A simple technique for beginner and professional photographers!!!

When I began photography, remembering the F-stop aperture intervals was the hardest and most frustrating thing. Mostly because the numbering is opposite to logical thinking unless you know what the number means. Logically thinking, a larger number would mean MORE of something. So if I wanted to increase the amount of light I made the aperture number larger (ex F/16 compared to the smaller number of F/5). Well that was wrong of course because the aperture designation is a fractional number.

An F-stop is a calculation between how wide the aperture blades will open (diameter) compared to the focal length of the lens. So if the focal length is 8 times the diameter of the diaphragm or blades opening, then the F-stop is F/8. A smaller number means the aperture blades are blocking less of the lens opening. The aperture blades on the chart below are represented by the inside circle while the lens diameter is represented by the outside circle. A larger aperture equals a larger circle.

F/2.8 has a wider opening and as such, allows in more light. Many times you will hear a photographer call a lens a "Fast Lens" which is a designation applied to lenses that have a maximum f-stop of F/2.8 or wider. See what I mean. Maximum would be considered in logical terms as a higher number (ie. maximum speed, maximum height, etc) but in photography terms it means the maximum the aperture can open. Photographers want wide, maximum openings in their lenses. You really don't have to know the math of calculating aperture. Just why that number is what it is and how it affects a photograph.

The first thing a photographer wants to remember are the aperture f-stop numbers. Start off with the full stops, which allow in twice the amount of light when opening and limit one half of the light when closing.
F-Stops in full stops -

1.4 -- 2 -- 2.8 -- 4 -- 5.6 -- 8 -- 11 -- 16 -- 22
<-------more light------------less light-------->

Going from f/4 to f/2.8 allows in twice the amount of light.

Going from f/5.6 to f/8 lets in half the amount of light.

Shutter speed is the same way. A larger number allows less light to hit the film plane. The shutter opens for 1/60th of a second or 1/500th of a second. The next thing (but not as important for reasons I will explain later) is to memorize the full stops of the shutter speed. This is also easier because all you are doing is doubling the number.

1/30 -- 1/60 -- 1/125 -- 1/250 -- 1/500 -- 1/1000 -- 1/2000 of a sec.
<---------more light---------------------------------less light---------->

Going from 1/250th of a sec. to 1/125th of a sec. lets in twice as much light.

Going from 1/60th of a sec. to 1/125th of a sec. lets in half the amount of light.

And finally there is ISO which is also easy to remember because just like shutter speed, you double the number for each full stop. But unlike f-stops and shutter speeds, this number is logical. Increase the number and you double the amount of light that the film/sensor will capture. Depending on your camera the number will start at a different figure. My Nikon D200 had a base ISO of 100 while my D700 has a base ISO of 200. I am going to use a base ISO of 200 for my numbering.

200 -- 400 -- 800 -- 1600 -- 3200 -- 6400 ISO -----> more light

ISO is how sensitive the sensor/film is to light. By increasing the ISO you are increasing the amount of light the camera can capture. Increasing by one stop lets the sensor read twice as much light and decreasing by one full stop lets the sensor read half the amount of light.

A photographer has to figure out what is the best exposure for a particular scene. In the old days you used and memorized an EV chart. These days it has become much easier to get a correct exposure (or in the ball park) due to technology. Cameras have built in meters that give a representation of the exposure via a histogram or plus/minus bar.

Below are three photos where I effected my exposure via one of the three main ways. Either increasing ISO, having a wide aperture or a mixture of aperture and shutter speed to get a correct exposure in a back lit situation.

digital photography exposure tutorial beginners

digital photography exposure tutorial beginners

digital photography exposure tutorial beginners

Over time and with experience, you will know the ballpark exposure setting for a particular lighting situation. After that you will fine tune the exposure via the histogram and for artistic taste. The first thing a beginner photographer needs to do is understand and hopefully memorize these camera settings. I stated them in full stop settings but most cameras will let you move between 1/3 stops for more control over the light. Recording light on a digital camera sensor is no different than the days of film. Digital photography has made it easier to get instant access to what the photograph will look like with a certain aperture, shutter speed and ISO setting combination. So as a beginner you should experiment as much as possible and over time you will master your camera exposure settings.


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