BitmapData.applyFilter brainfart

I am just not quite getting this. I think the docs for BitmapData.applyFilter indicate that these two should be equivalent under my circumstances, but they're not.
this:

Code:

---

obmp.bitmapData.copyPixels(vidmap, lpRect, origin);
obmp.bitmapData.applyFilter(obmp.bitmapData, obmp.bitmapData.rect, origin, reduceFilter);

---

and this:

Code:

---

obmp.bitmapData.applyFilter(vidmap, lpRect, origin, reduceFilter);

---

lpRect is the same size as obmp.bitmapData.rect. The way I read the livedocs, the sourceRect param should be the area on which the filter is applied, and the result of the filter should go into a rectangle of sourceRect size with upper left at the destPoint.

That is exactly what I see with the first method. With the second, it appears to draw about half of (the right half) that rectangle, and the left half comes from the upper left corner of the sourceRect. Am I doing it wrong?