hdr question

[marmots]

so i am trying to make a tone mapped HDR, but i am running in to a problem. after i have finished all the steps that i found on the internet, the finished image looks almost no different from the original.

here's what i am doing... i am using gimp, so i started with the correctly exposed image and added the dark image. then i went back to the dark image and desaturated, then applied a sobel-edge detect filter to the grayscale image. then i applied a very slight gaussian blur, so i used this as a layer mask to the dark layer. then i repeated with the bright layer.
and... nothing, there is a slight difference but nothing very noticeable

i tried this same process on two different images. now i notice that after i applied the edge detect almost nothing was visible so at this point i already figured something went wrong.

here are the original images i tried this on
( they were all raw so i just made the under\over exposed images from this)
i know neither of these pictures are very good but i was just trying to experiment