But when you render it you only get the background to where the ground plane finishes the top half is just white so i added the same background in the enviroment options in render to join the 2 together but the the enviroment backgrond is slightly diffrent colour,darker than the one from the ground plane.
Yah, and thats normal - you shouldn't bother too much about making a seamless transition, although it can be done. But it's a waste of time IMO. Just do the job in Photoshop.
And while you are in Photoshop, you can (should) also use the opportunity to tweak the colors and/or contrast. In the latest render, the car is too red. Do a quick and dirty feathered selection around the red parts (theres a gazillion of ways to do this), and desaturate it maybe 20-40% (sounds like a lot, but try it), while darkening it too - but don't darken too much - actually, you may want to darken most of the car, except highlights.
This is my first real render.
Quite happy with it, but still along way to go before I can compete with
any of the others here..
All the skins are made by Tsunami_sephi and are teamskins for our drifters
I usually do it like that most of the times, but it doesn't really matter if you have adapted a workflow using passes (I prefer to completely replace the BG in photoshop/compositing app, to get as much as possible back from the original BG picture, whereas in 3D, there are chances for increased or decreased RGB values - it's not difficult to make it match the original image though, but biggest issue is that most apps kinda change the image (interpolates the pixels even @ 1:1 render size, and you'll lose sharpness).