Depth of Field | Stop/Blur Motion | Equivalent Exposures

The Defense Information School, Fort George G. Meade, Maryland

Basic Public Affairs Specialist Course

Photojournalism

1

Basic camera techniques

Basic camera techniques will allow you to move your photography from merely recording a scene to capturing an emotion or putting motion into a still image so you can pass this feeling on to your viewers. These techniques will set you apart from amateur photographers. You will be a professional communicator using still images to tell your story.

Photo courtesy of Defense Imagery

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Depth of field Depth of field is the zone of acceptable focus in front of and behind the point of focus in your photograph.

Depth of field controls the amount of background and foreground that is in focus in an image. It helps you, as the photographer, direct the viewer’s attention to a selected area in your image. How do you know when to use more or less depth of field?

y When the background adds information to the photograph, use more depth of field.

y When the background is distracting, use less depth of field.

When using wide depth of field, everything in the frame is in focus, but:

Wide (or more) depth of field

y Everything in the frame is in focus y Can be busy y Everything in the frame is important

information

Shallow (or less) depth of field

y Foreground and background is blurred y Isolates your subject from the

background y Eliminates a distracting background

y The image could appear busy because the viewer has to mentally process everything in the frame. Everything in the frame competes for the viewer’s attention and can detract from your subject if it does not add information to the photograph.

When using shallow depth of field, the foreground and the background are blurred, leaving your subject as the only in focus element.

y Minimum depth of field isolates your subject from the environment, and it also eliminates or minimizes distractions in the frame.

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Home | Depth of Field | Stop/Blur Motion | Equivalent Exposures

Three factors control depth of field: f/stop (aperture), focal length of the lens and camera-to-subject distance.

1. F/stop

A large aperture, such as f/1.8 or f/2.8, yields a shallow depth of field, while a small aperture, such as f/16 or f/22, yields a wide depth of field.

The f/stop is a respresentation of the size of the aperture measuerd as a fraction. As such, the larger the f/stop the smaller the aperture.

f/2.8 f/22

Maximum depth of fieldf/22, 50mm lens

Minimum depth of fieldf/2.8, 50mm lens

f/1.8 f/8 f/22

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Three controlling factors of depth of field

Minimum to maximum depth of field

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Home | Depth of Field | Stop/Blur Motion | Equivalent Exposures

50mm lens, f/2.8 at 1/4000

20mm lens, f/2.8 at 1/4000

2. Focal length

The second controlling factor in depth of field is the focal length of the lens.Common lens sizes are the 28mm, 50mm and 105mm. The lower the number, the shorter the lens, the more depth of field the lens can produce.

y For example, a 28mm lens on f/4 at a distance of 25 feet from the subject will have more depth of field than a 105mm lens at the same settings.

Depth of field decreases with an increased focal length (given equal subject distance) and increases with a decreased focal length. In other words, if subject distance stays the same, a longer lens will provide less depth of field than a shorter lens (i.e., 105mm compared with 50mm or 50mm compared with 20mm).

Less depth of field is seen in photo above, shot with 50mm lens with f/2.8, than in

photo below, shot with 20mm with f/2.8 at same subject distance.

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Quick comparison

shorter lens = greater depth of field capability

compared with

longer lens = lesser depth of field capability

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50mm lens @ f/8 focused at 2 feet

3. Camera-to-

subject distance

The third controlling factor in depth of field is camera-to-subject distance.

The greater the distance you are from your subject, the greater the depth of field you can show in your photo. Depth of field increases as you back away from your subject.

Comparing camera-to-subject distances

Using the same focal length (50mm) with the same aperture (f/8): In the top photo, the camera is 20 feet away from the subject, and everything is relatively in sharp focus (foreground, background, etc.). This top photo shows a greater depth of field than the bottom photo, where the camera is much closer to the subject (2 feet away). In the bottom photo, only the subject is in sharp focus. The rest of the image is otu of focus.

Quick comparison

Longer camera-to-subject distance (further from your subject) = greater

depth of field

compared with

Shorter camera-to-subject distance (closer to your subject) = lesser depth

of field

50mm lens @ f/8 focused at 20 feet

DINFOS photos

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Depth of field is an important factor in bringing your images to life, but capturing movement in photos can add even more drama.

Adjusting your shutter speeds will allow you to stop or blur the movement or action that’s happening in your shot.

To stop or freeze action in a shot

y Use a fast shutter speed, such as 1/500ths to 1/16,000ths of a second, to stop, or freeze, the action as it happens in your shot. Stopping action is good for showing facial expressions, such as in dramatic moments.

y Select a shutter speed fast enough to stop the action, but avoid choosing extremely fast shutter speeds. The shutter speed you need to use to freeze the action will be dependent on how fast your subject is moving. A good rule of thumb is the faster the action the faster the shutter speed you should use. [See chart on next page.]

To blur action in a shot

y Use a slow shutter speed, such as “bulb” up to 1/400ths of a second (depending on the speed of the action) to blur the action (whatever is moving) in your image. Blurring action is useful to show speed, motion and energy or to create a certain mood in the image’s scene.

y Select a shutter speed slow enough to show the action, but avoid choosing extremely slow shutter speeds as focus may become an issue.

U.S. Coast Guard photo by Petty Officer 2nd Class Shawn Eggert

Photo by U.S. Marine Corps Pfc. Paul Zellner II, BPAS-W 030-08

Stop/blur motionThe helicopter blades are stopped/frozen in this shot, which was taken with a fast shutter speed.

The subject’s arm movement is blurred in this shot, which was taken with a slow shutter speed.

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General guidance on stopping/freezing action in an image

Shutter speed needed to “freeze” the action is dependent on the action:

Recommended Action Shutter Speed/s

Walking...................... (1/125 - 1/250) Jogging.......................(1/250 - 1/500) Running & Jumping.....(1/500 - 1/1,000) Helicopter Blades*......(1/1,000 - 1/2,000) Missile.........................(1/2,000 - 1/16,000)

* If you want to show some motion in a helicopter’s rotors, then photograph the aircraft between 1/60 and 1/250 depending on how far away you are.

This female airman’s “frozen” jogging action was captured at 1/200th of a second.

Photo

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Stopped action

Using a shutter speed of 1/800th of a second is fast enough to stop/freeze action.

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More stopped action examples

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Equivalent exposures Equivalent exposure setting refers to proportionally changing the shutter speed and the f/stop to control motion or depth of field while maintaining correct exposure for the shot. It’s used when you want to change how speed/motion or depth of field is shown in your image.

Why it works

Slowing down your shutter speed will increase the amount of time the light will hit your recording medium (the CCD), while closing down the aperture (increasing the f/stop number) will decrease the amount of light that stikes the CCD. If done proportionately, your exposure (remember E = I X T) will remain the same.

In the same aspect, speeding up your shutter speed will decrease the amount of time light is allowed to hit the CCD, while opening up the aperture (decreasing the f/stop number) will increase the amount of light that strikes the CCD. If done proportionately, your exposure (remember E = I X T) will remain the same.

How it works

When aiming to emphasize or change how speed or motion is shown in your image, make changing your shutter speed your first consideration.

When aiming to emphasize or change how depth of field is shown in your image, make changing your f/stop your first consideration.

Example: You want to place more or less emphasis on your subject

(change the image’s depth of field).

You have a properly exposed image using f/4 at 1/500th (according to your camera’s light meter), but want to place a greater emphasis on your subject in the photo. If you are trying to emphasize (focus on) your subject only, you will want to shoot for a lesser depth of field. With a minimum depth of field the foreground and background in your image will be blurred, but your subject will be in sharp focus.

To get a minimum depth of field, you may likely set your aperture at f/1.8 or f/2.8. [Remember, the larger the aperture, the lesser the depth of field.]

Using equivalent exposure setting - and the chart on the next page - if you change your f/stop from f/4 to f/1.8, then you’ll have to change your shutter speed to 1/2000th (see chart on next page) in order to maintain the correct exposure.

Similarly: If you are trying to emphasize both your subject and the environment, then you will shoot for a maximum depth of field, which will allow for all the elements in your image to be as in focus. For this, you will likely use f/11 or f/16.

Using equivalent exposure setting, if you change your f/stop from f/4 to f/11, then you’ll have to change your shutter speed to 1/60th (see chart on next page).

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Home | Depth of Field | Stop/Blur Motion | Equivalent Exposures

[Marked settings represent settings from example on previous page.]

Knowing first the shutter speed and f/stop settings that you must use to obtain correct exposure of your

subject in your image, you can use an equivalent exposure chart (such as the one pictured here) to determine the adjustment in the settings that you would need to

change for depth of field or motion (stop/blur) preferences.

Equivalent exposure chart

Shutter SpeedAperture (f/stop)

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Conclusion

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Using the basic camera techniques introduced in this lesson will help you become more confident in your photographic skills. They will also help you consistently take good photographs so you can communicate through your images what you want to communicate to your audiences more effectively.

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References

Home | Depth of Field | Stop/Blur Motion | Equivalent Exposures

London, B., Upton, J., Kobre, K., and Brill, B. (2001). Photography (7th ed.). Prentice Hall

Tompkins, A. (2004). The accidental photojournalist. The Poynter Institute. http://www.poynter.org/content/content_view.asp?id=65438 Retrieved May 11, 2009

Hurley, G. & McDougall, A. (1975). Visual impact in print.

Kobre, K. (2000). Photojournalism: The professional’a approach, Fourth edition. Focal Press

Upton, B. & Upton, J. (1981). Photography. Little, Brown & Co.

Morely, D. (1978). The focal guide to action photography. Focal Press, London England

Kerns, R. (1980). Photojournalism: Photography with a purpose. Prentice Hall

(1987) SECNAVINST 5720.44A: Public affairs policy and regulation. http://www.cpf.navy.mil/subsite/ehimemaru/legal/Exhibit_11.pdf Retrieved May 04, 2009

Nikon D70 owners manual

SB800 Flash Manual

BPASC Photojournalism Handbook (2009)