Convert twice and combine for perfect exposure.
TWO RAWS MAKE A RIGHT: STEPS 4-6
4. Now we'll put the image with the right sky (Sky.tif) on top of the one with the right land (Land.tif). Grab the Move tool (hit V on your keyboard), hold down the Shift key, and drag and drop Sky.tif on top of Land.tif. Holding down Shift aligns it perfectly with the layer below.
5. Next we have to hide the bad land to let the good land shine through. The first step is to add a mask to the top layer by clicking the Add Layer Mask button (third from the left on the bottom of the Layers palette).
6. We'll use the gradient tool for a subtle transition from what we want to reveal (the good sky on what's now the Background layer) to what we want to remain hidden (the too-dark land on the Background layer). Since we want the transition from good sky to good land to happen smoothly where they meet, start your gradient by clicking in the sky just above the land, and dragging down to just slightly below it (circled). If you don't like your work, draw the gradient again. It will simply replace the first. Keep trying until no one would ever guess you left the house without your gradu- ated neutral-density filter.
Make sure to draw your gradient on your layer mask and not on your image; you'll know it's selected when its icon has a little box around it. You'll know it's not if your image gets covered up by a big black-to-white gradient.