At 22:19 1/4/02, Albert wrote:
I was just reading some specs on most p&s. Most start at 1/250s!! WOW.
Some show 1/300s, and some go to 1/500's. I thought that was bad.. My
friend commented that is the same shutter speed, as a Hassy, so not a big
deal. YES, but a Hassy 80mm starts at F2.8, not F8!!
[snip]
The basic problem with P&S leaf shutters is reliability at faster than
1/400th second. The vast majority of leaf shutters go no faster than
1/500th, whether they're in a P&S or in a professional grade leaf-shutter
lens for a medium format SLR. The limiting factor is how fast the shutter
blade(s) can move. As shutter speed is increased, the length of time spent
fully open begins to converge to the time required for the blade(s)
movement to the fully open position. (Less of a problem at narrow
apertures than at wide ones.) If the shutter design allows too high a
shutter speed compared to how fast the blades move the result is uneven
exposure. Similarly, accurate exposure repeatability begins to suffer with
variation in how fast the blades actually move from one exposure to the
next. The practical design limit has been 1/500th second for many
years. Most P&S cameras top out at 1/500th, but some top out at 1/400th or
less. A very few claim speeds faster than 1/500th. I've been *mildly*
curious about their design and skeptical about their exposure repeatability.
My sister's p&s which she took on her honeymoon in Bora Bora, all the
shots came out blurry. She was UPSET!! I looked at the specs of her
camera. 1/250 and it started at F5.6. Upon closer inspection, I saw that
it did up to F11, so she had only 3 choices, F5.6, F8, F11. Actually, she
had no choices, the camera decided for her!
[snip]
Check out the exposure EV range of the camera for outdoor without flash at
each end of the zoom range (range of slowest shutter speed with widest
aperture to highest shutter speed with narrowest aperture). Then match
that with EV required for various consumer film speeds under "open shade"
to "sunny-16" conditions. After researching a large number of current
Can*n and Olympus models, nearly all of the aperture and shutter speeds for
the zoom lens models cover about 13-17 EV. The lower end is usually
bounded by widest aperture with a shutter speed that can be reasonably hand
held at max focal length. The upper end is bounded by narrowest aperture
and highest shutter speed possible at min focal length. This very nearly
independent of the camera's zoom range! ISO 200 film and outdoor daytime
conditions (open shade to unobscured, direct sun) spans about 12.67 to
16.67 EV. I've come to the conclusion the majority of zoom P&S cameras
have an EV range designed for using ISO 200 film outdoors during the day
(under conditions for which the integral flash would be useless).
The problem P&S users have with ISO 200 is trying to use it to make
"available light" photographs indoors, and at times around dusk or dawn,
with subject distances well beyond the range of the puny integral flash on
them. Classic example: a night or indoor baseball, football, basketball
or hockey game. The result is underexposure.
Lesson(s) I learned from this?
If thinking about a P&S, read their specs and determine what the usable EV
range is! For proper exposures, one film speed cannot "do it all." Try to
use ISO 200 films first. If there is a problem with frequent underexposure
because the user too often stretches camera capabilities in low light, then
try ISO 400. I don't recommend ISO 800 general use; only for very low
light conditions at distances the flash will not reach. ISO 800 runs into
too much overexposure in "sunny 16" conditions.
-- John
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