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Photography Question 
Blake T. Lipthratt
BetterPhoto Member Since: 9/30/2006

Why leave the shutter open when...

I've seen images on here that are taken in broad daylight, yet people still leave the lens open. I guess the image I'm directly referring to is Marc Adamus' image of a slot canyon.

The aperture is F/22 with an 8 second exposure. Why not just lower the aperture and have a faster shutter speed, lessening the risk for grain and lack of sharpness? Obviously, his image came out perfect, but do you not get the same result with other settings (faster shutter, wider aperture)? Help me out, I'm still learning...

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5/20/2007 4:41:09 PM

Bob Fately   Blake, ths short answer is that wider apertures create shallower depths of field - that is, the zone in which things appear focused. Depending on the effect you want, this might be desireable.

For example, if you are taking a photo on the beach of a friend, and there are a lot of other people in bright clothing in the background (or umbrellas and whatnot) then using a wide aperture can keep your friend in focus while keeping folks in front and behind him out of focus, thus lessening the distraction to the viewer's eye when she looks at the photograph.

Alternately, if you are taking a landscape shot and really want everything from the swingset in the foreground to the mountaintop in the background to be in focus, you will need to use a small aperture to increase the DOF.

DOF also depends on the angle of view of the taking lens - a wider angle lens has more DOF at a given f-stop than a telephoto lens would.

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5/20/2007 5:09:43 PM

Bob Cammarata
BetterPhoto Member Since: 7/17/2003
  Actually, a small aperture/long shutter speed equates to greater sharpness and less grain.

Less grain (noise) due to the low ASA setting required and greater sharpness because on long exposures, camera-shake caused by the shutter tripping has time to dissipate long before the available light begins to "paint" the image onto the sensor (or film).

Vibration caused by the shutter tripping typically lasts between 1/30 and 1/8 second. Many experts believe that at 1/15 second the camera "moves" during the entire exposure...even when tripod mounted.
It makes sense then to try to avoid that critical range of speeds and keep exposure times at 1/60 sec. or faster or use long shutter speeds when practical to do so.

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5/20/2007 5:52:04 PM

Samuel Smith
BetterPhoto Member Since: 1/21/2004
  bob c has it right blake,i really am not sure of his explanation and all the tech stuff,but it just works in many situations.
even with mirror lock up,it may effect the outcome.

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5/20/2007 7:57:51 PM

Sherry K. Adkins
BetterPhoto Member Since: 5/13/2006
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  Blake, to answer your question, I have been to the slot canyons and there is no direct light. In these canyons the light can be very low, even in the middle of the day. So Marc had to leave the shutter open for several seconds. He also used a small aperature to have a greater depth of field. If Marc had used a faster shutter speed and larger aperature, he would have lessened his depth of field.

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5/20/2007 9:45:14 PM

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