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Category: Photographic Field Techniques

Photography Question 

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Shutter Speed and Aperture Settings


I have a Nikon F70 and I dont know how to use the shutter speed and aperture settings. I'm a beginner and love photography.


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July 25, 2001

 

John A. Lind
  Exposure 101:
The combination of shutter speed and lens aperture set the film exposure, and this you undoubtedly already know. Most cameras allow the user to set them in full "stops."

Shutter speed is set in seconds and fractions of seconds, 1, 1/2, 1/4, 1/8 . . . 1/125, 1/250, 1/500, 1/1000, etc. Following the sequence, the shutter is open half the time in going from one shutter stop to the next.

Lens aperture is set using an f-number. This system was devised to create a common system of setting lens aperture so that the scheme means the same on any lens of any focal length. The f-number is the focal length of the lens divided by the diameter of the aperture. If you have a 100mm lens and the (effective) aperture is 25mm in diameter, the lens is set at f/4. For f/4 on a 200mm lens the (effective) aperture would have to be 50mm in diameter. An f/4 setting on any lens admits the same amount of light as an f/4 setting on any other lens.

Common f-numbers found on lenses are: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, and f/16. The higher the f-number the smaller the aperture opening, and less light is admitted. These, just like the shutter speed settings, are full stops. There are other numbers found, most often for the widest possible lens opening, such as f/3.5 or f/4.5 (these are 1/3 stop larger and smaller than f/4). Partial f-stops are almost always found in 1/3 stop increments.

Amount of light admitted by an aperture is directly related to the its area, not its diameter; area is directly related to the square of the diameter. If you double the diameter, you quadruple the amount of light. If you triple the diameter the amount of light goes up by nine times. That's why f-numbers are in increments of the square root of 2 (1.414 approximated).

Since shutter speed and aperture settings move in equal increments, you can trade shutter stops for aperture stops and have the same exposure. This gives you a range of aperture openings and shutter speeds that you can use.

What determines the required exposure? Basically it's subject brightness and film speed. This is a more complex subject in application because of the need to define what the subject brightness is. For most users, the averaging system of some type performed by the metering built in to the camera works under nearly all conditions.

Advanced users sometimes concern themselves with the the brightness level of the brightest highlights and deepest shadows in which detail is desired, and make decisions about how to average the two. Under some conditions, the difference between them is greater than the film can capture (the contrast is greater than film latitude), requiring more decisions on what to give up, some of the highlight or some of the shadow.

Control of shutter speed is most often desired to stop motion or prevent camera shake from causing visible blurring. Control of aperture is most often desired to set depth of field, the range around the lens focus distance which will appear in focus.

-- John


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July 29, 2001

 

Roland Towey
  Hi, when you say you don't know how to use shutter & aperture, do you mean you can't operate these functions? I too have the F70.

To set shutter, press 'function button' on left hand side. While holding this down, turn dial on right hand side. You will notice arrow in green area of display. When you turn the dial, the arrow moves into different sections. Stop arrow in area with letter P. Now depress SET button on left hand side and turn dial at same time. You will notice P turns to S or A. When S is displayed turn dial and you will see the shutter speed increase or decrease depending which way you dial.

To set aperture, follow the same steps until A appears in green zone. Don't forget to release the clip on the aperture ring. Turn the aperture ring on lens - you will notice f numbers increase or decrease.

Hope this is of use to you. It was said by critics that this camera is brilliant once you have mastered the controls. I agree. But with a little practice you to will be able to operate easily. I am very happy with the F70.


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August 03, 2001

 
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