Water splash photography - Post processing tips requested

[k.udhay]

Hi,

I went through this tutorial in youtube and want to try out:



@2.29 - The video author shows a fantastic final pic.
@ 4:45 - He shows just-out-of-the-cam (unedited) pic.

The unedited pic. has got one big problem. The black background colour under water lever is a bit of grey compared to the one above. And it is very prominent too. I have a couple of questions here:

1. How do I eliminate this in camera shoot stage itself?
   
2. If to be done in post processing (preferably Photoshop), can you give me the brief steps? Any online tutorial link will be very helpful.

Ultimately, I want to get an output as in 4:45. And, I want to be as prepared as possible before I shoot. Thanks!