Sounds to me like you mean applying effects.
In Vegas, you can apply effects at four levels - to the "clip" (or "event" in Vegas terminology), the track, the media or the production. Or all four if need be.
My guess is you are applyng an effect to the "media" - you do this by right clicking the event and selecting "Media FX". This affects, as you have discovered, the whole captured element.
To apply efects to an event only, you click on one of the symbols at the right hand side of the event on the timeline. You'll probably see two little icons there, the top one is the Pan & Crop icon and the lower one is the FX icon.
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Tim
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