At 19:12 3/24/02, Moose wrote:
Perhaps John "11x16" Lind or a lurking Gary "Stop that Vibration" Reese
know more?
OK . . . I'll add my $0.02 worth. It's anecdotal from practical
application and what I "get away with" when making my photographs. In
general, for the mid-range 28-75mm focal lengths Dave originally mentioned
at 1/250th second, a tripod won't make much difference provided the person
holding the camera has a good solid stance. I feel more comfortable at
1/500th toward the longer end of that range. If DoF doesn't matter much I
tend to push up toward the higher shutter speeds. The two pics I made in
Wyoming were both hand held out of perceived necessity. Having had
shooting training courtesy of Uncle Sam, I use some of those techniques for
very solid bracing with a camera.
From a standpoint of image acuity, shutter curtain travel time doesn't
affect much, if anything. It's the amount of time any one point on the
film is exposed to light that does count. I suppose it's possible to
introduce a slight amount of image distortion as the camera will have
shifted by the time the slit makes it from one edge of the film frame to
the other, but at a 1/250th shutter speed, no single point on the film is
being exposed for more than 1/4th of that.
Tripod usage serves two purposes: camera shake mitigation and aiding
thoughtful image composition. How much it contributes to shake mitigation
depends on shutter speed and focal length. Contribution toward thoughtful
composition remains nearly constant, and it helps greatly with keeping a
level horizon when using 24mm and shorter lenses. It is *very* easy to end
up with a slanted horizon when hand holding the 18mm in particular; I
always try to use a tripod with it. I suspect users of the 21mm have
encountered similar issues with it also.
Two recent examples:
The one of the "Secret Wyoming Factory" using the 135mm was done in a
*sitting* position with legs crossed at the ankles and elbows braced just
behind the kneecaps. Took a little repositioning of feet and knees to
compose it. Looking at the projected Kodachrome I know it can make an
11x16 OK. Knowing the shake risk with a 135mm I also made a half-dozen
shots; several repetitions of a couple different perspectives (horizon
position). Took risks making it that way though. The mountain pic with
snow fences was easier with shake risk in using the 24mm. The significant
risk with it was keeping the camera "level" (roll, not pitch; I
deliberately aimed slightly downward). The rolling and sloping terrain
didn't help. I was either kneeling or sitting for that one also. A
combination of not only bracing but to get closer to the ground and pick up
closer foreground easier for a feeling of greater image depth.
All that said, I would have preferred to tripod both. The consideration
was being parked barely onto the unpaved shoulder of I-80 with a large
number of tractor trailer rigs whizzing by at 80+ MPH. I didn't want to
stop any longer than necessary and decided to forgo the time required to
set up the tripod. Less time parked in both locations meant: (a) less risk
to getting hit by a big truck with a highway-hypnotized driver, and (b)
less risk of encountering one of Wyoming's "finest" who might not take
kindly to someone parking on an interstate highway shoulder to make
photographs.
-- John
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