DSLR Recording Time Limits
The maximum recording time depends on the model of your camera. For the newer Canon DSLR models the time limit for one movie clip is 29 min. 59 sec. After this, recording will stop automatically and you’ll have to press the start/ stop button to resume recording. Interestingly, Canon implemented this time limit because recording longer than 30 minutes would classify the camera as a video camera. Why is this bad? Because in some parts of the world there is a 5.6% tax on video cameras. So DSLRs avoid this tax by only allowing shooting times less than 30 minutes.
A solution to this problem is to install the free Magic Lantern software. One of the many features that Magic Lantern offers, is the ability to automatically restart recording once the camera reaches the 29 minute limit.
Memory Card Too Slow
If you notice that your camera frequently stops recording, it may be because your memory card is too slow. Memory cards come with varying read and write speeds, which means how fast the card can store and retrieve information from and to your camera. The higher the memory card class number (Class 10 vs Class 6) the faster the read and write speeds. For DSLR video work, it’s recommended to use at least Class 6 cards, if not higher. If the memory card is too slow it won’t be able to keep up with the amount of information the camera is trying to feed into it so the camera will stop recording.
Movie File Size
Because of the way DSLRs work in conjunction with the file structure of the memory cards, currently the maximum file size is 4 GB. If you are recording a movie that exceeds 4 GB in size, the camera will continue recording but the camera will automatically create a new file. This means that during playback you’ll have to play the individual movie files. If however, the movie file size begins to exceed the amount of space available on your memory card, then the recording will stop, and the camera will display an error message. Remember to always pack lots of extra memory cards so you’ll have lots of extra memory space on hand.
Another reason that your camera may have stopped recording is because it overheated. There’s a safety mechanism that will automatically stop your camera if it detects that the camera is overheating. In this case, you can physically feel that the camera has become warm to the touch due to overuse. When this happens, just turn off your camera and let it rest and cool off. Thus, if shooting professionally it’s always best to carry a back up camera in case you might miss an important event while you wait for your camera to cool down.