Replying to Photoshop CS4 Extended help.

So ive been working on some HDR photography and it seems like the photo's I give photoshop do not have the correct exposure values. So when I try to merge to HDR it think that the higher exposure value is a lower exposure value. The low exposure photo and normal exposure photo's work fine. This causes a really bright completed image. Is there a way to manually tell Photoshop which photo is which? Or is there a way to alter the photo's data to adjust the photo's exposure value? The photos are coming from Gran Turismo 5's photomode. I'm thinking that there camera doesn't input the correct exposure values into the file (although photo's look how they should) I'm using Photoshop CS4 Extended FYI.