Actual vibration testing bears out some of what you say and not others. The tripod leg material has a direct effect on the time it takes to dampen down a vibration. It has to do with the ability of the material to absorb a vibration that hits it instead of creating harmonics. Aluminum is the worst material when it is a hollow leg construction. It takes close to twice as long to dampen out as it does compared to wood, especially a dense wood like ash. Even a leg brace has little positive affect. However filling the hollow leg with something like lead, sand, etc., will reduce it to a value consistent with other materials. Mass in this case overcomes the materials natural tendency to create harmonics and absorbs most of the vibration. Also hanging a heavy mass from the center post of the tripod can dampen vibration out much quicker also. Kent Gittings
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of P�l Audun Jensen Sent: Friday, November 02, 2001 4:22 AM To: [EMAIL PROTECTED] Subject: Re: Shutter Vibration Tested (RE: K2 shutter vibration question) David wrote: >The key to getting rid of vibration is that no amount of attached mass is >really >going to help. You need something to absorb the energy, otherwise known as >damping (no, not dampening with water:). > > I've been playing with gently resting my hand on the 6x7 when its on the >tripod. I got that tip off a long-lens technique web page I read somewhere, >where the guy recommends resting your arm over the lens to absorb >vibrations. He said its the only way to get sharp photos with the big >glass. I >reckon a small sandbag resting on top of the rig would also do the trick. This may be true in theory but in real life mass has everything to do with it. In fact, a real lightweight tripod won't work regardless of what material its made of. Mass provide the inertia to prevent vibrations in a tripod. It ensure good mass coupling, which is really what a steady tripod is all about, like bolting the tripod firmly to mother earth. It also prevent external vibrations from eg. wind to reach the camera. Damping of vibrations is good in theory but a tripod/head job is to prevent vibration in the first place and for this you need great mass coupling. Wood and carbon fiber work not because of damping but because of a more favorable strength to weight ratio. OF course, damping of the tripod legs may be very important if you knock on the legs during exposure, but this is not how vibrations usually originates. It starts in the camera and if the camera is allowed to vibrate because of inferior mass coupling, no amount of damping in the legs can prevent the image from becoming fuzzy. When the vibrations have reached the legs then its too late because they have already shaken the camera/lens. The reason why holding your hand on a super telephoto for damping vibrations works is that its the camera lens system that vibrates, not necessarily the tripod legs (provided that the tripod is reasonable calibrated for the job). The mass coupling is really lousy for long telephotos due to excessive unsupported weight. It wont really help to have tripod legs that dampen vibrations - you need something to dampen vibrations where it originates and that in the lens/Camera system. P�l - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org . ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept by MIMEsweeper for the presence of computer viruses. www.mimesweeper.com ********************************************************************** - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
