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Photography Question 
Tam B. Howland

shutter speed and f stop

I just started getting into photography, and I am getting very confused about how the fstop and shutter speed work there a easy way to remember how to use these?

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3/2/2008 6:53:22 PM

Not really, Tam. Thre is no shortcut to success. You will need to actually understand the function of each and their effect on the others. F stop and shutter speed are not the only ones. There's also ISO setting, White Balance, Depth of Field, distance to subject, and perspective distortion. And many, many more.

You will need to read up on those. Try the search function of this board. is also a good source.

But welcome to the world of photography! It can be a fascinating field of interest if you're prepared to put some time and effort in.

Have fun!

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3/2/2008 9:10:27 PM

Carlton Ward
BetterPhoto Member Since: 12/13/2005
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  Hi Tam, Think of the f-stop as a pipe and the shutter speed as the valve that controls the amount & time the light goes through the pipe.
f/2.8 is a large pipe and so to get enough light recorded on the sensor to capture the image will be very short (so you would open & close the valve very quickly). f/22 is a small pipe and it will take longer for the light to go through and record the image so you will need to leave the valve open longer. (Slower shutter speed)
This is the simple explanation but there are more variables involved such as how bright the light is (bright sunny day or overcast or morning/evening light) and also the ISO setting you are using. the Higher ISO settings like 800 or 1600 will record the image faster and is used in low light situations but you run the risk of noise (called grain with film) and ISO 100 is slower but is better quality & usually preferred. So its actually the 3 components 1. f-stop 2. shutter speed & 3. ISO setting that work together to create a proper exposure. It gets deeper than this when you consider DOF (depth of field) and using all of these settings and their properties specifically selected to create artistic images, and please ask if you want to get deeper into that discussion. Hope this helps - Carlton

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3/2/2008 9:16:20 PM

Alan N. Marcus   Hi Tam,
The controls you are inquiring about revolve around four factors. Nobody said it’s easy; you will need to spend time studying all four. The good news is, modern cameras with their chip logic reduce the necessity for you to understand f/numbers (aperture), shutter speeds, ISO, and the light level, however mastery of these four factors are a requisite if you are to seriously pursue photography.

The whole thing is comparable to getting a drink of water at the sink. You go to the sink with an empty glass. This glass has a line drawn on it (ISO). Your task is to fill the glass exactly to the line. The factors are: Water pressure (light level) – size of pipe carrying the water (aperture f/number) – time the faucet valve is open (shutter speed).

ISO: Now the size of the glass establishes how much water is required. So too film and digital chip have a requirement, they need a specific quantity of light. Too much water overfills, too much light over-exposes, too little water under-fills, too little light under-exposes. Now the measurement system for water is ounces or milliliters, in photography the light energy requirement is set by a unit called ISO (International Standards Organization). Say your chip/film needs 100 units of light, more results in over-exposure, less results in under-exposure. Generally the photographer is allowed to choose the ISO value he/she will use. We would choose a higher value for night work or a lesser value when at the beach. 100 ISO is typical, 200 ISO needs half again less light energy, 400 ISO is half again. Higher values are termed “faster” meaning less light will do the job because a faster the film/chip fills more rapidly.

Shutter speed: When filling the glass you work the handle turning on the water and then off (time). The camera shutter is a clock mechanism that does the same thing. Traditionally camera shutters follow this sequence. 1 – 1/2 – 1/4 – 1/8 -1/15 – 1/30 – 1/60 – 1/125 – 1/250 – 1/500 – 1/1000. These are fractions of a second except the first which is a complete second. It is important to note that each value going right is twice the speed of its neighbor to the left. So if the camera is set to 1/60 second, the light is allowed to play on the film for one sixtieth of a second, a specific time, change to 1/30 and the light is allowed to play twice as long whereby 1/125 allows light to play half as long. Generally the faster values like 1/500 or 1/1000 and used to arrest action at sporting events while 1/15 or 1/30 allows light to play for a very long time thus we often use them when the light is feeble. Note the sequences follows a pattern; each is twice as fast going right and twice as long going left. This sequence allows control in increment steps which are a doubling or halving i.e. 2x incremental change in speed thus a two fold or halving of the amount of light energy allowed to play on the film/chip.

The f/numbers: The f/numbers tell us about the working diameter of the lens. The larger the working diameter the more light that is permitted to enter. The lens is modeled after our eye. Our eyes have an iris that gets bigger in feeble light and tiny in bright light (the colored portion of our eyes named for the Greek goddess of the rainbow). This is duplicated on the camera lens and is called the aperture. Because the aperture is a circle the language here is based on circle geometry. The labeling is strange, it’s: 1 – 1.4 – 2 – 2.8 – 4 – 5.6 – 8 – 11 – 16 – 22 – 32. Your camera will not have all of these values maybe yours will have the range 2.8 ~ 22. The tiny values like 1.4 or 2 tell us the lens is wide (big) allowing enormous amounts of light to enter the camera. The large numbers like 16 or 22 tell us that the aperture is tiny so only a meager amount of light can pass. Note each value is a 2x change. Going left, each allows a two fold increase in light energy to play on the chip/film. Going right, each reduces the light energy playing on the film/chip in half.

Light level: Bright sunny days have a light level or pressure. Indoors in a dim room the light pressure is low. Your camera features a light measuring system that will measure the light level and help you choose the settings of the three other factors you are required to set to obtain a correct exposure.

Again ponder the four factors involved getting a drink of water at the sink.

How much water (light) needed is determined by the size of the glass (ISO).
The water pressure at the faucet (light level).
How much water can flow determined by pipe size at the faucet (aperture).
How long the tap is open (shutter) determines the volume of water that flows in a given time.

Alan Marcus (dispenses marginal technical gobbledygook)

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3/3/2008 8:49:07 AM

Irene Troy
BetterPhoto Member Since: 5/27/2004
  Hi Tam and welcome to BP! You have already received some excellent advice, so I’m only going to make one other recommendation: go to the library, bookstore or wherever you can find it and get Bryan Peterson’s book on Exposure. It is, by and far, the best resource for really understanding the many factors involved in determining correct exposure. My first BP class was with Bryan and it was a real step forward in my learning photography. Unfortunately, he no longer teaches here, but his book is really good.


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3/3/2008 10:27:57 AM

Tam B. Howland   Thank you everyone for all the responses, I am looking forward to using the info

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3/3/2008 10:43:38 AM

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