The effect isn't visually outstanding.
There are two things that u want to achieve with this effect
1) the 3D effect
2) the contrast of the coloured subject on a monochrome background
However, i find the 3D effect isn't prominent enuff. Yeah, the drop shadow is there, but somehow the shadows fades away in the dark gray tone of the boulders.
Also, the contrast between the coloured and the monochrome isn't intensive enuff. The coloured background inside the frame is mostly gray (rocks) with white (sky), which is similar to the monochrome background outside the frame, thus resulting in a rather flat effect.
Try to use another pic to push out the drama of this effect.
Just my 2 cents
