Taking great photos
This is my first post on any website so I hope I am writing this in the correct spot!!! There are alot of opinions on how to make "average" photos better. All of the suggestions on this thread are great! I have a different perspective of encouragement to Jarred! Great Job in capturing this one-time event!!!! You learnerd the science, followed the steps, and took initiative. You got to the right spot at the right time and brought your camera. The most important thing, in my opinion, is that YOU captured the shot. This is science first, art second. Any numscull can go to that one tree in that one forest 7, 8, 9 times until the lighting, atmosphere, mood is just right, set up the carbon 6 Gitzo with remote, put the 1DS mark II on f/22 and blah blah, take 100 images and go back next week for a "better" shot. That's not, or shouldn't be, the focus on storm chasing. You've captured valuable information that we should be honored to view!!!! Thank you for that.
On the note of fixing your image: See if you can get AT LEAST Photoshop CS. All images from any digital camera stink until you clean them up in Photoshop first. That is your lab, your darkroom. I use "Shadow and Highlight" first to elliminate most of the under and over exposure in the same image. Then I use levels to increase midtone contrast by bumping up the midtones and shadows manually. Then, I use the dodge and burn tool to bring out the clouds without blowing out the highlights and bringing detail in the grass. Finally, I add color saturation if it needs it, to give the photo more pop. AFTER all of this if you really care about the rule of thirds, you can crop the image any way you like. You did right by getting as much of the storm in your photo as possible. You can always take away, but can't add.
If you want to really make your images amazing, after Photoshop, open your image in "Neat Image" and clean up the digital noise. None in this photo, but great for long lightning exposures. It will make the clouds seem fluid while keeping sharpness in the image.
As far as cropping this image, I would leave ALL of the grassy field (bottom-weighted) and crop the very top of the cloud just where it seems to break up. Crop just enough to make the top solid. Your grassy field is a great anchor for the photo and gives the illusion of distance, depth, and cloud scale. It also makes the photo more dramatic. Rule of thirds is a tool if you need it. The rule of the rule is that once you understand the rule, you have permission to break it!!!
I can help you with photoshop if you like. Give me a hollar. I can send you a copy of your image with some sample CS processing if you like, but I won't copy it without your permission since it's copyrighted!
Thanks for sharing this awesome photo!!!
Greg Cranwell