[Don Hoey]

Having swapped my 80-200 zoom for an old AIS manual focus 400mm lens. sorting possible tripod mounted vibration problems was todays mission. I had read Bjørn Rørslett's review, and although he gives it a good score for image quality, he does note that as it is a light lens, 1200 grams, it is prone to vibration when tripod mounted. As for image quality I was very impressed with performance when used on a monopod yesterday but had concerns over the tripod mounting bit.

With dismal light again today I decided to measure ( clock it ), when mounted on the Manfrotto sliding plate for the 501 fluid head. This was done by clamping it in a machine vice on the milling table so a very solid clamp. Although the lens has a good clamshell collar the pliable rubber on the sliding mounting plate allowed for a deflection of 50 thousands of an inch. I made a intermediate plate of significantly greater surface area that could be mounted on the lens then screwed using 2 screws to the sliding plate so compressing the rubber better and over a greater area. Back in the machine vice and the set up was reclocked. The maximum deflection under a load has been reduced from 50 to 2 thousands of an inch. The plate has effectively added 500grams of mass to the lens. Hopefully this will counter vibration problems noted by Bjørn. The clocks do not register mirror up or shutter movement, but mirror down gives about a thou of movement. Still the shutter has closed then so it should not be a problem.

When we get some decent light I will give it a proper test.

I knew Rob would have a good laugh, so I took a pic of the final clocking and have attached it.

Don