Why is there a limit restriction to the 1080p film video recording time duration on DSLRs?
- that the processing hardware gets hot, so the limit extends the life
- EU classification of camera as camcorder attracts duty
- FAT32 file size limit of memory cards is 2gb, but then you could chain the recordings seemlessly together "spanning" and have a playlist metafile to link them (how do PVRs cope)
- size of memory card, well just get a bigger one?
Is this limitation still prevalent, are there DSLRs out there prosumer and entry that don't have the limit. And why do those that have it, well have it?
As far as I know it is a legal thing to prevent extra import duties in the EU. Until Canon or anyone officially state that, it will remain speculation.
It's not a heat issue, as a) if the sensor had heat problems they would likely occur before 30 minutes, and b) after one 30 minute capture the camera will allow you to immediately begin another 30 minute capture!
There is a separate limit of 4GB due to FAT32, you actually hit this limit first if you're recording in full HD resolution. Yes manufacturers could work around it by spanning, but what's the point? DSLRs were never designed to be video cameras, for most people the current limitation should be plenty. If you want to record entire concerts/weddings/events from a fixed camera, then a video camera is a better option all round.
I believe there are hacks to the Panasonic GH1 which remove time limits to video recording.
If I were Canon, I would sell the camera with restriction deliberately in the firmware to enable it to sell cheaper without added import duties, and if EU laws are the sole reason, I would offer a free firmware download, or via their open Canon Firmware toolkit (CHDK - chdk.wikia.com ), i.e. open source parts of the firmware that deal with recording duration time, for developers themselves to turn this restriction off, then canon wouldnt be liable.
But why go to all that trouble? The original purpose of the video feature added to the 5D mkII was to allow photojournalists to capture short video clips to upload to the web so they could do double duty whilst in the field. That was it. Hence no 24fps or 29.7fps modes. The whole video DSLR craze caught them by surprise a little, but even the serious filmmakers using video DSLRs wont have a problem with a 30 minute limit - when was the last time you saw a film with a 30 minute take?
In short, the only people who are likely to care about there being a 30 minute limit are those who want to plonk the camera on a tripod and record their kid's graduation ceremony or whatever. If you're going to do that, you probably don't want shallow depth of field anyway so you might as well buy a cheap video camera that will go for four hours.
what Matt says. No serious videographer is going to want to use a DSLR to shoot for more than a few seconds (I one-up him here, I know), and most casual users will start finding it cumbersome after a few minutes and throw away the results anyway because of the camera shake, poor dof, and other things in which their video isn't what they'd expected after seeing the home videos shot using real videocameras on America's funniest once too often.
+1 x 2 Matt Grum on comments and +1 on answer for confirming my guesses in my question and for the point on longer single-shot footage times not being necessary in most film situations. For me, it's not a deal-breaker to have such a restriction as I would tend to work on short films and music videos.
+1 already given, but this point "when was the last time you saw a film with a 30 minute take?" makes one think. It's true, one doesn't find such a length.
Accepted answer, because it's most comprehensive and thoughtful, key point being unneccessary requirement for long clips, but also what set your answer out from the others was the thinking about overheating (if you can restart a recording again), also for discussing hacks to override the limitations. Credit given to everyone else for their time and answers; the fact that some overlap with the same gives strength to those answers.