Re: Off Topic: Lens advice

Message posted by gary on May 04, 2002 at 21:13:00 PST:

Canon EOS will autofocus to F8, but the performance is pretty dicey. That particular lens is image stabilized and has an ultrasonic focus motor. I don't have any IS lenses, but all the Canon lenses that I own are USMs. They focus much faster plus have the option of manual focus after autofocus if for some reason you don't like the focus or it autofocused on the wrong area. At 400mmf5.6, you should be able to get by without image stabililation with iso 100 film outdoors. [You will have to pan your body to track the plane, so I don't know how that would effect the IS.] I'd say for taking photos around the base, a 400mm prime focus would be fine. It doesn't even have to be autofocus if you don't mind buying another camera body. You will find that the Canon EOS will not work with a telescope, that it, it will not meter properly, so you will have to buy another manual focus camera. It will be considerably cheaper to buy the large aperture telephoto in some older mount, like Pentax screw. It is not that difficult to focus a telephoto lens since the depth of field is so shallow. My Canon 10s is pretty old and won't autofocus reliably with the 400mmF5.6 if the object does not fill the viewfinder, so I end up focusing by hand.

What ever body you buy for a telescope, make sure there is a companion magnifier for the viewfinder. You won't be able to critically focus without one. The Nikon F3 with DW4 is nice in that it has a 6x magnifier that allows you to see the whole frame, but it is a luxury. You can focus just as well with the magnifiers that snap on the viewfinder. You will also need to find a camera that has a simple ground glass focusing screen (or interchangable screens) to focus a telescope.

Looking at Bill's photo, I should be that lucky. Generally when we hang out at Coyote Summit, the planes are on the other side of the highway. Looking at the topo map, they hug the hill about 0.7 mile from our location. With a 400mm lens, they fill about 1/3 of the viewfinder. When the planes sneak behind us, they are about 0.3 miles away. I think Bill's photo was done about 1500ft and must have been really fun to experience.

In Reply to: Re: Off Topic: Lens advice posted by Koji on May 04, 2002 at 20:21:20 PST:


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