If your shot is too light or dark, there's not much you can do. When you brighten or darken a shot, you lose definition. And if you lose definition, you will further distinguish the edited footage from the rest of the video. If it's just a little light or dark, you can use a filter, play around with the contrast, saturation, and other tools at your disposal. But short of making the rest of the video equally dark or light after your best fix, there's not a lot you can do with badly lit footage.
Resizing An Image
If you have shot the footage in HD (and what video production company is using standard definition these days?!) you may be able to zoom in on someone in the edit to 'make them bigger'. Whenever you 'tamper' with a shot and try to make it something it isn't, you always risk having it look altered or different from the rest of the video.
Remember, not all HD is the same. There are many 'flavors' of HD video production, ranging from consumer level to shooting features. Think about it. You can't expect the camera you bought at your favorite electronics store for a couple of hundred dollars to compare with a camera that costs hundreds of thousands of dollars that they use in Hollywood. So take this zooming in on the shot with a grain of salt. If it's a low level HD camera, the footage you zoom in on may look pixilated (jagged) compared to the rest of the video.
Cut-Away's to the Rescue!
Whether you need something to masque a bad shot, fix a continuity problem, cover someone frowning in an interview, or a myriad of other problems that come up in the video editing process, extra shots that you can cut-away to can be your best friend!
You never know when you'll need them, so take a little extra time to record close ups, wide shots, product shots, and other shots that you may need to either enhance your video production or get you out of a jam when you're video editing. Production companies in Chicago, for example, may use shots of downtown skyscrapers as cut-aways in a corporate video.
Take a few beauty shots too. Though they may not be called for in the script, record anything that looks attractive and is relevant to the video. You never know when you'll need them or even want to use a few to replace the original shot you planned to use. As a video production company, pays off big time in the long run when customers begin to notice the quality of the work!
The bottom line is think things through as much as possible in pre-production and then get the right shots, as well as extra shots during production, so you don't have to scramble during the video editing process.