Boyd Ostroff |
April 10th, 2006 07:13 AM |
Quote:
Originally Posted by Tom Bolia
this WA acts more like a fish eye with that much curvature and distortion. And is it normal for either the WA or TELE adapter to show through the viewfinder/lcd screen? The WA has the corners curved off (blackened), and the TELE is like looking through a tube. Are these what are considered as not "zoom through" adapters?
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What brand of adaptors are you using and what are their specs? They are identified with a number followed by an "x" which indicates their amount of magnification. For example, a 0.5x wide adaptor would make the field of view twice as wide as normal. In other words (thinking in 35mm still camera terms), it would turn a 50mm lens into a 25mm lens. Same thing with telephoto: a 2x adaptor would turn that 50mm lens into a 100mm lens. If your wide adaptor is more extreme than .7x then very likely it will have some degree of a barrell distortion (the curvature effect) unless very high quality.
The cheap adaptors can be pretty bad and introduce a lot of distortion (the curvature you noted). If they aren't properly designed for your camera you will also get vignetting (dark corners like you saw). Some adaptors are designed such that you can zoom through the full range on the camera and still hold focus, others are not and will go blurry at some point in the zoom.
Telephoto adaptors - even the good ones - are rarely full zoom-through. Since you're magnifying the image you generally reach a point somewhere around the middle of the zoom range where they begin to vignette. Then as you go all the way to full wide you will get the "looking through a tube" effect you mention, where you have a black field with a circle in the middle.
As a basic principle, wide adaptors should only be used at the wide end of the zoom range when you can't get as wide a shot as you'd like. Same thing for telephoto: use it at the telephoto end of the zoom when you need more magnification. Do some tests to see how far you can zoom with each lens before you run into trouble. Also remember that your viewfinder/LCD doesn't show the full image all the way to the edges, and a consumer TV won't either. However if you watch on a computer you'll see everything and you may discover that the corners are cut off when you didn't realize it. Connect the camera to a monitor with underscan or to your computer running your editing software in order to see everything when you do your tests.
Also remember that no matter how good these adaptors are, adding glass in front of the camera's built-in lens is going to lower your quality somewhat. Glad we got your basic problem sorted out though. As I mentioned, this happened to me once and it can be very disturbing!
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