Hasta La Motion!

I created a gray swatch in photo shop and graded in with apple color using only the luma curve. I then brought both the non graded and the graded swatches into shake and used the LookupHLS node with iEXPR selected to match the grades. I was able to get an exact match on the pixle anayzer but I was expecting the curves to match in both programs. Can someone that knows both programs explain to me what I am missing here and why the representations are different in these two programs?

Here is exactly what I am talking about:

http://www.vimeo.com/3478081