Oh yes that video :rolleyes: which proves, to a high degree of certainity, that if you balance a penny on a hassie and fire it then the penny won't budge.
The question is, what else does it prove
Well I disagree. I can handhold to that speed for sure and get acceptable sharpness. The "trick" is not to use the shutter release at all but to use the timer instead. If you do that you will find that 1/5 is difficult but not impossible. It is a low probability shot under many conditions, but one in two or three shots will be just fine if the wind isn't blowing too hard
Originally Posted by Sirius Glass
But I do agree, Steve, that a hassie (or rb) is certainly handholdable to 1/60. If that's really what you want to prove then why not simply show shots taken handheld at 1/60? The penny thing proves nothing in this regard.
Along those lines, this shot was handheld at 1/15 or 1/20, as I recall, with a mamiya 645 afd. 1/60 is nothing.
If I use a short shutter speed, I do not notice any difference because the shutter speed is fast enough to freeze any movement caused by mirror vibration.
If I use a long shutter speed, I do not notice any difference because the mirror vibration time is insignificantly short compared to the long amount of time the shutter is actually open.
I do, however, notice image degradation caused by mirror vibration when I mount my camera on a telescope and use a shutter speed between 1/2 second and 1/15th second. Thank goodness my SLR's mirror lock-up feature is very useful for avoiding this degradation.
All of this, agreed. Sometimes.
Originally Posted by Sirius Glass
All of this, disagreed. Mirror slap does indeed show an effect, in common conditions with a normal lens, even up to 1/125 and beyond. See Thornton 2000 pg65 for one published example... there are many to be found on the 'net of course. That said, proper holding or stabilization technique can mitigate though not eliminate the effect, and some bodies are more prone than others (bodies for formats larger than 35mm seem to suffer less, I'd imagine--but don't know--because of their weight).
Below 1/[lens focal length] it becomes necessary to use a tripod or set the camera down on a stable surface, some for sooner than others. The duration of mirror slap is so short due to dampening that a 10 second exposure is not going to show any effect, but it may be wise to lock up a mirror on long exposures as a good practice.
Reciprocal of focal length is overly optimistic in my experience. Most folks without training can effectively handhold at one to two stops faster than that, no more. Average person seems to need 125 or 250 on a 50mm lens on 135 to get "acceptably" sharp [edit to add: at 8x10 or above, depending on the image you might not notice the effect enough to be a problem at smaller sizes]. But, that's one that people can and do argue about endlessly, so, to each their own experience.
Hey, cheers for not taking it seriously. I'm new to this forum and so far it seems much more pleasantly easygoing than most. I will say that the PhD "rocket scientists" and fluid dynamicists and whatnot that I work with have often forgotten how to tie their shoes at this point though...
Since I have been an engineering professor and technically I am a rocket scientist I will ignore the comment about asking a high school physics teacher posting on line for advice.
Think of the Pentax 67. It's mirror is larger and heavier, with greater inertia and momentum, but it illustrates the concept of image degrading mirror induced vibration. A 35mm slr's mirror is smaller, but so is the film size, which needs to be enlarged (along with any lack of crispness) to a greater degree, to obtain the same final print size.
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Originally Posted by JBrunner
Hand held? Probably not.
On a tripod? Probably.
A rangefinder just is not the kind of camera I would use on a tripod (or any 35mm camera, for that matter, except for in uncommon situations)...therefore, the lack of a mirror has no advantage for me. It is not one of the advantages of a rangefinder, IMO (in terms of "camera shake"...not in terms of lens design/collapse-ability).
"Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."
- Rob Tyner (1944 - 1991)
I recently tested some of my cameras on an old rickety tripod to test the shaking that each camera showed. A laser pointer was strapped to each camera. Here are the results I saw, observing the light about 30 feet away, and with each camera on "B.":
Canon F-1 (new): 0 shaking. Very damped mirror/shutter. That's probably why they left out a mirror up feature on this model.
Bronica S2: Even with a huge, noisy mirror, very little vibration.
Leica M2: some side-to-side shaking in certain circumstances. This can be felt even when off the tripod.
Pentax k20d: definite side-to-side movement, in spite of vertically-travelling shutter. Impossible to dampen, even on larger Gitzo CF tripod.
The laser pointer and penny tests don't really tell you if the vibration is affecting the image. There could be a lot of vibration when the mirror returns and the shutter closes, and that wouldn't make any difference.
The Pentax 67's problems are also due to the shutter curtain. See the illustration, even with the mirror locked up, here:
Originally Posted by frank
Thanks for that link. Here's a quote from that site:
Originally Posted by olwick
The problem I experienced requires some further explanation. The Pentax has a large rapid-return mirror. At slow shutter speeds (below 1/125 second) and especially with long lenses, it should be locked up. This is SOP (Standard Operating Procedure) for all medium format cameras, and should be even for 35mm cameras. Mirror shock is a real sharpness thief for critical work.