Last summer while I was visiting Alberta and BC, there was one evening where a spectacular storm rolled in during the evening hours. Being on flat terrain, the lightning was visible for nearly an hour before the storm eventually reached me and the rain began. This presented a wonderful opportunity to take a variety of photos of the approaching clouds and lightning. It was a rather frustrating process as timing your photos correctly to actually have a bolt of lightning appear in a photogenic way was difficult, not to mention that your exposure could be greatly affected if a greater than expected discharge took place.
I eventually settled on an exposure of 8-10 secs, at f8 and ISO100, which gave me sufficient depth of field for this purpose, and the longer exposure time allowed slightly more leeway for exposure variations and timing. In full disclosure, I did significantly cool the white balance in post processing to achieve the bluer tones, which are actually quite accurate to what I saw, just not what the camera interpreted of the scene.
Be sure to click on the photo for full web sized! Even at that resolution it doesn’t do this photo justice at all, and I wish I felt comfortable to share a high resolution image without having to worry about others using the image.