ac130/ac160 and flash band detection system ?

[Jan_Crittenden]

Hi,

So the fact is that the AC130/160 do not include the Flash Band Compensation. Think about it this way. The JPX250 was built and design and based on the same DSP that is in the HPX370 body. So it has the FBC and the PAP filter. The AC130/160 was designed by the AF100 design team. Think AF100 with small sensor. The three cameras are similar in the ULT chip pset but from that point on they are different. The 160 has VFR in 1080, up to 60P, the HPX250 only has 60P overcrank in 720P. The HPX250 has some cool features esp like AVC-Intra, and it is the first camera under $6000 that has a full professional codec. This is major! The AC160 is a great little camera with its VFR, Function knob fine tunig for the Auto Focus and its long lens. Both cameras have attributes. The difference between the 160 and the 130 amounts to 4 features, no VFR, No uncompressed Audio, No HD-SDI and only 60Hz.

Hope this helps,

Jan

[Barry_Green]

Let me point out that when Jan says "only 60Hz", she's not saying that the AC130 only shoots 60p/60i. It does of course also offer 24p and 30p. What she's saying is: the AC160 is switchable between NTSC 60Hz and PAL 50Hz, whereas the AC130 isn't - it's NTSC/60Hz only for the USA model.

These two cameras (160 and 250) are going to be a little confusing for people, I can't wait for the demands for "just release a firmware update so the 160 can be 10-bit like the 250"... but it isn't so. The outer shell is the same, and the lens and sensors are the same, but everything after the sensor is different. The DSP is different, all the processing and image manipulation is different, the recording is different, the hardware inside the shells is all different. The 250 is 10-bit, and has the FBC and the 2-stage P.A.P. filter. It has the 370's controllable peaking and its "system" menu. Its DRS works differently, its knee works differently. Most of the menu items are the same, but the actual camera implementing those menu items is different. The 250 really is an HPX370 squeezed into a handheld body, with some VFR added for undercranking in 1080 mode. The 160, on the other hand, looks like it is an AF100 with a fixed lens and 1/3" chips. Its menus look and act exactly like an AF100's (with the addition of dual slot recording). It has the same "function knob" functionality, which the HPX250 doesn't even have; even though the bodies are similar, the 250 doesn't have the function knob, it got replaced with a "User Main" button. The 160's innards and outputs are based around 8-bit because that's what the engineering and architecture of the AF100 were.

The choice between these two is not going to be obvious; each has decided advantages. The AC130 is the real "no brainer" of the group -- if you were gonna get an HMC150, the AC130 is better in just about every way, except that it's physically bigger (and, of course, if someone wants/needs CCD chips instead of MOS sensors, the 150 offers them). Other than that, the 130 bests the 150 across the board. And if you can stretch to the 160, it's just better than the 130; VFR and uncompressed audio and SDI and NTSC/PAL switchability are all definitely worth it to me, but for those who don't need those features, the 130 is just plain compelling.

When it comes to 250 vs. 160, it's all about the $1,000 price difference and the cost of P2 cards. If those are an insurmountable obstacle to you, the 160 is the choice. If those are a non-issue to you, take a good long look at the 250 -- it's the lowest-cost 10-bit recording camera on the market. It's almost certainly going to meet with full BBC approval, for those who shoot for broadcasters with those standards. It has niceties like spot zebras and user-adjustable peaking. It's 4:2:2 from a full-raster chipset, recording 10-bit to the highest-quality recording format ever put on a camcorder, and it lists at under $6k.

Even if you could afford it, though, if you're an AF100 user, you may find the 160 a lot more user-friendly and compatible with your workflow. Same AVCCAM recording, same menu system, same features, same 1080 overcranking, same function knob, same color and tone and image processing, same knee and DRS functionality. Whereas if you were an HPX370 user, I would think the HPX250 would be the obvious companion -- same 10-bit workflow, same P2 workflow, use your same cards and readers, same menu structure, same functionality throughout.

[Phil1076]

I'm really curious whether the footage from the AC130/160 will be distinguishable from that of the 250 to the naked eye, without pixel peeping.

[Barry_Green]

I'm really curious whether the footage from the AC130/160 will be distinguishable from that of the 250 to the naked eye, without pixel peeping.

For most folks, on neutral shooting situations, with no grading: probably not, except that they do have somewhat different color reproduction and the knee and DRS functions work differently between the 250 and the 130/160.

If you do heavy color grading, the 10-bit and 4:2:2 of the HPX250 is definitely going to make for a better end result.

When the AF100 first came out, the crews guys in NZ did a test with it and AVC-Intra and posted their side-by-side screen grabs, and most folks were hard pressed to tell the difference. But that was also simplistic style footage.

in summary, AVCCAM is really surprisingly good, and a lot of folks will be very happy with it. But undoubtedly AVC-Intra will be superior. It just depends on whether you need that level of superiority and are willing to pay for it.

[Phil1076]

What would be a good example of footage that would cause a noticeable difference between the two codecs? Fast motion? Bright highs/low shadows in the same frame?

[Barry_Green]

Well, the three things the HPX250 has over the AC160 are:
1) 4:2:2 color sampling. Most noticeable in greenscreening, or in heavy grading.
2) 10-bit quantizing. Will provide smoother gradients, so skies or anything that's gradient will be rendered at a lot higher precision, and again this will really show in post grading.
3) Intraframe compression. Intraframe is more robust and consistent. Long-GoP codecs can potentially degrade a half second of footage if the codec is overloaded to the point where it can't quite cope with all the detail that's being handed to it. Now, this is much less of a concern with AVCHD than it was with HDV. You can see some examples of how this happens in my article in the Articles section where I compared AVCCAM against XDCAM-EX. In most scenarios the two codecs looked nigh unto identical, but when the going got rough XDCAM-EX puked much worse than AVCCAM did. AVCCAM held up better under stress. But an intraframe codec would hold up even better. The thing is, the h.264 codec is 2x to 3x more efficient than MPEG-2, so it's a lot harder to break it. You'd have to go to a daylit forest with tall grass blowing in the wind, and a river splashing through it, to really find the kind of detail that would stress AVCCAM to the point where you were seeing noticeable softening and blockiness in the footage. It just doesn't happen all that often in normal shooting scenarios.

AVC-Intra is a world-class, top-end codec. It's the premium codec that the BBC chose for their Digital Media Initiative -- when they go digitally archiving everything they've shot, they do so to AVC-Intra. It's the best of the best out there that you can get in a camcorder. AVCCAM is its little brother. It's in fact quite good, surprisingly so, but it isn't AVC-Intra.

That has its own set of advantages, of course... you can record 12 hours of footage on a single 32GB memory card, for example. You can't do that with AVC-Intra! You can put AVCCAM in the low-bandwidth HE mode, which uses only 6 megabits, and record for hours and hours and hours. You can get six hours of best-quality footage on a 64GB card. With AVC-Intra, you can only get one hour on a 64GB card. So in terms of ultimate image fidelity, no doubt, AVC-Intra is superior. But in terms of practical usage, there are some scenarios where AVCCAM just makes more sense (longform recording of a concert or play, for example; I know Ullanta here frequently records three-hour operas on his cameras and finds it a lot more practical on AVCCAM than it would be on AVC-Intra). But for mission-critical work where you need the ultimate image fidelity, AVC-Intra is superior.

[zijital]

How much difference would there be between a 160 & 250 both plugged into a Ki Pro ProRes Recorder (or whatever gets you past the internal codec)?

How much more does the 250 offer over the 130/160 when you hit the internals of the camera past the chips?

[Mike Warren]

How much difference would there be between a 160 & 250 both plugged into a Ki Pro ProRes Recorder (or whatever gets you past the internal codec)?

How much more does the 250 offer over the 130/160 when you hit the internals of the camera past the chips?

I don't know how this translates in terms of actual picture quality difference, but the 160 only outputs an 8 bit signal, whereas the 250 is 10 bit. In theory, it should allow much more latitude when grading. It's not just the 4:2:0 vs 4:2:2.

[zijital]

Only 8 bit? That frakin' stinks. Didn't see that before, that makes a difference too & disappointing.

I'm guessing no chance of that getting upgraded in future firmware, right?

[Mike Warren]

I'm guessing no chance of that getting upgraded in future firmware, right?

I don't know for sure, not having access to Panasonic's code, but I think it's extremely unlikely. The DSP is less powerful in the 160 and odds are they're handling the signal as 8 bits all the way through.

But just having the extra 2 bits is not enough to guarantee better dynamic range, at least not 4 times the DR as is implied by the 2 bit increase. I'm sure there will be other limiting factors in the sensor block.