Size of render region == size of result image

When I need to render some part from the camera view I use the render region (Shift + B). But the image is 100% size (empty around region). How can I get a permit as a selection?

Better for 2.49, please)

You want to set the render resolution to 800 x 600, and then render a portion of that resolution at 800 x 600?

Blender 2.49b - Select the ‘Crop’ button in the render settings (Format panel)
Blender 2.54 - Select the ‘Crop’ tick box in the render settings (Dimensions panel)

organic, resolution of this portion must be smaller than fully render. Sorry, i know english a little. Richard Marklew helped me what I need!

Richard Marklew, what i am inattentive! Thank you very much!