Shooting lightning is, for me at least, challenging and at times a bit scary. Here's a capture from one week ago, 8/4/09. Huge fast-moving storm, SE corner of Rocky Mountain National Park at about 9:30 PM or so. I used a Canon 1D MKII, 24-70 L zoom at approximately 35 mm, ISO 100, BULB mode, manual release timed to capture multiple flashes, in-camera noise reduction on, tripod:
Shooting these in RAW file format is important because white balance must be corrected due to the long exposures. The usual approach of framing the picture, fiddling with various settings etc. isn't practical. I pre-set the aperture between F8 and F11 and focus at infinity. Sure I got a bit wet, as did the camera/lens/tripod - but I don't worry about weather much because the 1 series Canon bodies and the L series lenses have excellent weather seals throughout.
In this case I was lucky to get some very powerful near-by ground strikes in rapid succession. One trick I've discovered is to release the shutter (terminate the exposure) the very instant a big strike occurs. The fine branching away from the main bolt is better preserved and the inevitable over-exposure is minimized. Regarding post-processing, little is required beyond cropping, white balance and additional noise reduction on occasion. The last thing I do to these in post-processing is use my sharpen brush at 2-4% in the 'lighten' mode applied to the lightning itself. Regarding the powerline in OP's image - I'd eliminate that in a heartbeat with no qualms at all. Instead of the clone/heal tool, I use polygonal lasso with a 1 pix feather, select closly around the offending line then move the selection adjacent to the line, copy, paste and move to cover the line, then flatten as this technique rarely requires additional adjustments. For lighting strikes that aren't strong enough for my taste, I will sometimes use the high pass filter to sharpen the lightning detail. (post-processing tools and terms above are from Adobe Photoshop, CS4).
