Posted by Jeremy (209.112.95.68) on December 31, 2003 at 17:39:33:
In Reply to: Re: appropriate shutter speed posted by mikeb on December 27, 2003 at 17:10:23:
The rule for handholding a shot is to use at least the reciprocal of the lens' focal length. For example, if you are shooting a 200mm lens handheld, you would want at least a 1/200s shutter speed. Therefore, with a 160-400mm lens, you would need at least 1/400s to have a chance at a sharp pic.
The thing you need to consider is that the focal length doubler will add two stops of light. For example, if you have an 80-200mm f/4-5.6 lens, it will become a 160-400mm f/8-11 lens! That is going to make it very hard to focus properly. The microprism will be completely useless, and most likely, so will the split image.
As mikeb suggested, the image quality might not be the best. It won't be as good as a professional 400mm f/2.8 to be sure, but it might be good enough for your purposes/budget.
A trick I like to use is to prefocus. I think this would work with bird photography if you are careful and deliberate. Focus carefully on something the same distance as the bird will be (if the bird isn't there) Then, wait patiently for the bird to show up and snap the picture.
Another thing you should remember is that you shouldn't be handholding pix like that if at all possible. Brace against whatever is available, whether it is a tree trunk, or your knees when you squat down to the ground. You will get sharper pix no matter what focal length you are using.
Lastly, you might consider lookin on eBay for an inexpensive off-brand lens to mount on your camera. I had an old 300mm f4 lens with stop-down metering which I sold on eBay for about $20 a couple years ago. It was a universal mount lens, which had to be screwed into a K-mount adapter to be used in my K1000, but it was certainly better than a 2x doubler with a zoom lens.
Take care,
-Jeremy
end of archived message