deep etching

Probably you'll want to draw a path in the shape you want, and use Clipping to hide the part of the image outside the path.

Possibly you could convert the image to a pattern, and use a pattern fill of whatever closed path that you draw. It's hard to say which way would be better, without knowing more about what you're doing.

Thanks for the response Brynn,
I may be over complicating the Q...
I want to (for example) import a photo of a tree, then select the tree, and remove it to use alone in a drawing.
You may be right on how to do it (without a magic wand/ lasso) by drawing a path around the object in the photo and then clipping out the rest of the photo....but how do i do it? Is the most effective way?
Cheers

Oh ok. Clipping definitely the way to go, if you need to "cut out" a specific part.

I would do it with the Pen/Bezier tool. Zoom into the imported photo, and go around the border, placing nodes in the highest and lowest points of curves. After you're finished, you'll probably need to go back and tweak the new path using nodes and node handles.

Or you may be more comfortable using the Pencil/Freehand tool. Just drag it like a real pencil, around the border. The more you zoom in, the better the result will resemble the photo. There's a setting on the Pencil control bar, which will help make a smoother line, and create fewer nodes. I would put Smoothing around 50, then adjust to your needs.

If in the photo, the tree is very well defined against its background, there's a way to do it sort of automatically. Assuming the tree is well contrasted from the background, after that it depends on the kind of tree and how much detail you need to retain. Here's info on that technique in the manual: http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Trace-SIOX.html (Note that's a poor example in the manual. This technique really can produce better results than that cat illustration.)

Yeah, there's no "magic wand" in Inkscape.

Ha ha
Unreal, success! I had found that section on the manual but was a bit bamboozeled....simply clipping works just fine for me.
Thanks very much, I appreciate your help
Cheers

You're welcome :-)