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From: James Nagler on 1 Jun 2010 09:27
On Tue, 01 Jun 2010 09:12:04 -0400, John A. <john(a)nowhere.invalid> wrote:

>On Tue, 01 Jun 2010 07:50:03 -0500, James Nagler
><jnagler(a)spamproofed.net> wrote:
>
>>On Tue, 01 Jun 2010 08:17:06 -0400, John A. <john(a)nowhere.invalid> wrote:
>>
>>>On Tue, 01 Jun 2010 10:34:23 +0100, Bruce <docnews2011(a)gmail.com>
>>>wrote:
>>>
>>>>On Mon, 31 May 2010 19:53:06 -0500, Rich <none(a)nowhere.com> wrote:
>>>>
>>>>>Bruce <docnews2011(a)gmail.com> wrote in
>>>>>news:3su7069evkcm3kbkvaqriu3btr2s534ro1(a)4ax.com:
>>>>>
>>>>>> On Mon, 31 May 2010 10:18:39 -0700 (PDT), Rich <rander3127(a)gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>>On May 31, 10:12�am, Bruce <docnews2...(a)gmail.com> wrote:
>>>>>>>> On Sun, 30 May 2010 08:58:15 -0700 (PDT), RichA <rander3...
>>>>>@gmail.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>> >Perfect example. �Guy shoots a Panasonic GH1 hand-held at 1/3 sec
>>>>>and
>>>>>>>> >f16 and wonders why his shots aren't sharp. �P&S's are weaned on
>>>>>>>> >cameras that have infinite DOF and limited apertures (often don't
>>>>>>>> >close down to lower than f6.3) so to them, the discipline needed to
>>>>>>>> >shoot a DSLR or EVIL camera is alien.
>>>>>>>>
>>>>>>>> >http://forums.dpreview.com/forums/read.asp?forum=1041&message=
>>>>>35451698
>>>>>>>>
>>>>>>>> I have been posting exactly this view - that P&S users will encounter
>>>>>>>> focusing problems with Micro Four Thirds and larger sensors - for
>>>>>some
>>>>>>>> weeks now.
>>>>>>>>
>>>>>>>> They do say that imitation is the sincerest form of flattery, so I
>>>>>>>> thank you for your sincere flattery. �;-)
>>>>>>>
>>>>>>>Good thing though, the EVIL cameras have much less shutter slap and
>>>>>>>are able to produce sharper images with extremely long lenses.
>>>>>>
>>>>>>
>>>>>> The only camera I owned that had a problem with shutter slap was a
>>>>>> Zenit B 35mm SLR, and that was back in 1973.
>>>>>>
>>>>>> I must give shutter slap some credit, though. It is a red herring
>>>>>> that has been around for a great many years, but still appears fresh
>>>>>> to some people. ;-)
>>>>>>
>>>>>>
>>>>>
>>>>>Not a red herring. Shots with a D300 with mirror locked up showed 1/2
>>>>>the sharpness of the Panasonic G1 when shooting through a 1000mm lens.
>>>>>With normal, even heavy duty tripods, damping out all motion with such a
>>>>>lens is nearly impossible and the Nikon's shutter had sufficient slap to
>>>>>induce motion that could not be controlled.
>>>>>Modern Photography did tests of film cameras for blur from vibration and
>>>>>they ended up having the lash them to a brick wall in order to control
>>>>>it, because some were just too jarring when fired. Trust me, I've used
>>>>>lenses past 4000mm in focal length.
>>>>
>>>>
>>>>You want me to trust you? A bit of a stretch, I think ..
>>>>
>>>>Seriously, though, I accept that there might be a problem at longer
>>>>focal lengths than I normally use. I rarely go beyond 300mm but I
>>>>have just bought a 400mm lens so I will carefully monitor the results
>>>>for shutter slap. Perhaps I will need a heavier tripod. ;-)
>>>
>>>You'd think the heavier lens would help, but maybe the greater moment
>>>arm counters that. Depends on the lens, I guess.
>>
>>My 16" diameter (20" dia. OTA) reflector telescope weighs a total of 255
>>lbs. when completely set up. The cast-iron mount and counter-weights alone
>>weighing in at about 150 lbs. of that. Yet I can lightly tap the telescope
>>tube and it take about 20-40 seconds for the vibrations to completely
>>dampen down. (The "tap test" is well known to amateur astronomers, anything
>>under 60 seconds for vibrations to dampen down is considered "good".) It is
>>a well balanced telescope, just a standard 9v battery is enough to power
>>the tracking and go-to system (it is that well balanced). But at high
>>magnifications (600x-1000x) even the slightest disturbance will set up
>>visually obvious oscillations.
>>
>>The speed with which a mirror and shutter in a DSLR is moved is like
>>sharply tapping that telescope tube. You can obtain Sorbothane� pads that
>>can be placed under each foot of a tripod leg to help dampen vibrations
>>more quickly (popular with astronomers) specifically designed for tripod
>>use, but the initial movement will still impact short exposures.
>>
>>There's no free lunch with the mechanical contrivances in a dSLR. The only
>>way to take a vibration-free image is by opening the shutter (securely
>>mounted on a sturdy and dampened tripod) in a totally dark room and using
>>an off-camera flash to expose your subject 30-60 seconds after you have
>>opened the shutter. Off-camera flash is required because the firing of the
>>flash itself imparts an impulse of motion.
>
>Perhaps some sort of counterweights in the camera, moving opposite the
>mirror & shutter, would help. Are there higher-end cameras with such
>features?

Any camera with a symmetric leaf-shutter design. (This includes most all
P&S cameras.)

From: Pete on 1 Jun 2010 13:20
On 2010-06-01 14:12:04 +0100, John A. said:

> <snipped for brevity>
>
> Perhaps some sort of counterweights in the camera, moving opposite the
> mirror & shutter, would help. Are there higher-end cameras with such
> features?
>
> Making the moving parts of the mechanism more lightweight would help
> too.

Counterweights and damping are applied.

The shutter mass is a trade-off: speed, accuracy, life, and cost.
Accuracy is aided by the use of a self-monitoring shutter.

The mirror mass is reduced in some bodies by giving the finder a 95%
view instead of 100%; this also allows a smaller body size.

--
Pete

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