Photoshop?!?!?!?

So Im able to fix over/under exposed pics...but now i have a picture thats literally half and half...how do i fix both sides?Photoshop?!?!?!?
curves.





put three points on the default line





one in the middle.


one closer to the bottom [where the perpendicular lines cross]


one closer to the top [where the perpendicular lines cross]





the bottom one represents shadow


the middle represents midtones


and top represents highlights








adjust these until they are accuratePhotoshop?!?!?!?
What happened ... did someone shoot using flash at too high a sync speed? Usually when that happens one half of the exposure is correctly exposed.





You may have to carefully cut the image in half and then correct the exposure and then reunite them. Care will have to be taken to make sure the gamma of both halves are identical. Be sure to save the original file somewhere safe in case you have to send it out to a pro retoucher.
Are you familiar with Layers and layer masks?





I'd suggest doing one layer fixing each aspect (I mean, one layer fixing overexposure, one layer that fixes underexposure) and then applying a layer mask to each.





Using a soft black brush (size dependent on your image) Fill in the part you DON'T want to see.





So, if the right side is underexposed, Duplicate the layer, apply your tricks to it, and then apply a vector/layer mask. Then fill in the left side accordingly to where the lighting is off. Repeat this for the overexposed layer.
Use the lasso tool and cut the photo in half by cutting and pasting it. You will probably have to mess around with the feathering feature on the lasso tool to get the two halves to fade into each other. Once you have the two separated, adjust them. It sounds easy, but it may take a while to get it just right.