New JVC HM850 & HM890 cameras
- Thread starter vanvideo
- Start date
That's oodles more light than I had - I make horror movies. More than sensitivity, the unpredictability (IE - the difficultly repeating results) of what you'd get from day to day was the problem.
Regardless, I'm sure these new cameras are better. Are they $8,800/$9,800 better than a used GYU100 ($200 the going rate w/o lens on ebay today)? That remains to be seen.
http://www.ebay.com/itm/JVC-GY-HD200CHU-Mini-DV-Digital-ProHD-Video-Camera-Camcorder-/151210961894
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Snowblindform - XDCAM EX has been given broadcast approval by the EBU for "journalism" usage, and has been widely adopted by broadcasters for news and other factual programmes around the world. In the UK, that includes the BBC amongst others, where it's currently their codec of choice for such work.
Given that, to call it "a border line consumer codec" is frankly ridiculous.
It is completely wrong to just go by compression system and bitrate alone. As much depends on other "non-headline" factors as on bitrate itself.
If you want just part of the detail, then in a long-GOP format, a crucial fact is how to allocate data between the I-frames and difference frames. In a simple system (as may be found in a consumer camera), that allocation may be fixed - x% always allocated to I-frames, y% always allocated to difference frames. In a more complex system, the allocation may be dynamic. With little movement, little detail gets allocated to difference frames. With high movement, less to I-frames, proportionally far more to difference frames. The result is that the overall quality equates to a far higher bitrate in a simpler system with fixed allocation.
But it comes at a price of a far more complex encoding engine to do it in near-real time. All of which is why XDCAM is primarily found in more expensive cameras, and why it's performance is so much better than the 35Mbs figure would initially suggest. (Certainly when referred against early and consumer HDV cameras.) It's a professional codec, albeit on the lower tier.
It's also why comparisons against 45Mbs on such as GoPro and Canon consumer are meaningless in isolation. They'd only have validity in an "all else equal" situation, and here this is far from the case. Can you tell me how the Canon consumer cameras allocate bitrate between I and difference frames, for example?
But again, headline specs can be highly misleading. The XF100 only has a single 1/3" 1920x1080 Bayer chip. Consequently, it's inherently going to be over a stop less sensitive than 3 1/3" chips. And such a Bayer design only has 960x540 red and the same number of blue photosites, and that's going to set a limit on it's chroma resolution. Yes, about half of 1920x1080 both horizontally and vertically. So even if the recording codec is 4:2:2, the front end performance of the camera won't be able to advantage of it - you'll only be getting the equivalent of something like 4:2:0 out of the front end.
So whilst the XF100 may have a better codec than XDCAM EX, the front end (although far from bad) means the overall camera doesn't even make it into Tier 1 for broadcast.
steve phillipps
Veteran
Good headline specification with these new cameras is the 1080 / 60P - very impressive......but....at that rate the 50 mb/s codec is going to be pretty compressed. 50 mb/s has been a benchmark for broadcast and a feature of this new camera is that it has it, but I wouldn't be surprised if there will be a specification of 100 mb/s required for 1080/60P content? The same is true of the new Varicams - according to the literature it will only do the 240fps HD in the AVC Intra 100 codec - that's a LOT of compression needed!
Steve
Steve
Not as bad as you may first think. Firstly, it uses H264, and that should give compression efficiencies over MPEG2 (at the expense of requiring more processing power to work with). Secondly, remember these are INTERframe codecs, and a characteristic of such is that doubling framerate *DOES NOT* mean a doubling of coded bitrate for the same quality - nowhere near.
The principle is that I frames still occur at the same time interval - so typically every 1/2 second - but the GOP length is increased, so more difference frames between the I frames. Since the I frames are by far the biggest, and you keep the same number, that means the datarate overall doesn't rise very much, all else equal.
And it's been covered in the other thread, but don't worry about the Varicam compression. 240fps will keep the same frame compression - but will mean about 800Mbs in AVC-Intra Class 100. You won't want to record at that frame rate for very long!
steve phillipps
Veteran
O, so not twice as compressed - but more compressed nonetheless, but yes, good point.
Steve
Steve