I will admit, I have been guilty of accidently shooting video vertically instead of horizontally.
I don't do it on purpose, but there are many who do - and to that I say, "STOP IT!"
This is not a matter of personal preference, video is meant to be viewed horizontally.
Look at your TV, look at your computer monitor, look at the movie screens, they are all horizontal!
If you look at a video shot horizontally on your TV vs a video shot vertically you will see how much of your picture you are losing out on.
Plus, the black bars that surround your video are not attractive, and are just a waste.
If I haven't convinced you yet, think of it this way...
if you have HD video that you are shooting vertically, you are wasting the HD quality by forcing it to display incorrectly.
Next time you are about to take a vertical video - JUST STOP. Stop recording and turn your video horizontal.
If you want to know how to shoot perfect video, here are the top 5 things to consider:1- Don't take long boring videos. Certain moments are precious & need to be captured. Getting a great shot of your daughter as she kicks a soccer ball is great, 30 minutes of her running back and forth on the field, game after game... not great.
2- Stop using the zoom so much. If you need to zoom in or out, do it slowly and gradually. Quick zooming can make the viewer sick, and zooming too far into a shot will just give you a shaky video.
3- Avoid Backlighting. Don't shoot a person standing in front of a window or open door. The excess light behind the person will make them appear dark in the video.
4- Whenever possible, use a tripod. Video that is shaky & moving from side to side is no fun to watch and ruins the moment.
5- Be prepared. Make sure your batteries are charged and that your SD card is has plenty of space. Then plan for problems, bring an extra battery, extra SD card, tripod, and power cords, extension cords, & lens cleaner.