Jim E. Brooks
Mirror lens vs. longer zoom
I work as a staff writer/photographer for a small newspaper, and use a couple of Minolta Maxxum 400si bodies with a variety of lenses.
I've been in a couple of situations where my 70-210 zoom isn't enough zoom, and I was unable to get closer to the fire or accident. Most of these have been in daylight conditions.
I'm thinking of buying a 500mm mirror zoom lens. I've been reading about some of the facts of life regarding these lenses (fixed aperture, doughnut ring distortion in background), but I want to know how they perform in the field. Or should I consider a 300mm zoom?
From the sounds of your needs , you would be just as well off with a good seven element doubler/ tele-converter
it is known by either name , but I call it a tele-converter.
it comes in several magnafications.
a 2x would turn your 210 into a 420mm.
You will lose speed , just as you would with lets say a 500mm f8 mirror lens.
the image quality will be better in that you won't get the tell tale donuts in the out of focus erea.
I can not help thinking that you will not be happy with either set up for the work you do. They are not hand hold arrangements. On the other hand a fast large telephoto or zoom can be very expensive. I almost missed the part about the 300mm zoom , still not the best for hand holding at max zoom but better.
|Charles W. Craft||
I'd tend to agree with everything Dana said. From experience, the cheap (under $200) "f8" mirror lenses tend to be close to an actual f16. They're so dark they're almost impossible to focus, and the depth of field, even at long range, is very shallow. They're also not very sharp. There's no way to get acceptable handheld results except in bright daylight with fast film and a lot of luck.
The better ones (I have a 400-600 Pentax zoom) can be very sharp, but at those lengths, are still not handheld propositions. The ring distortion looks a little strange, but even worse is a doubling effect I've noticed in bird pictures. The subject (a bird in a tree) is in sharp focus, but the branches immediately behind are not only blurred, but doubled -it's really wierd.
I'd try the converter first.
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