GH5 180fps frame rate

BobKo

BobKo

Well-known member
I read a couple of reviews of the GH5 that praised the camera but suggested that going higher than 120 fps in variable frame rate mode was not good. Yet I routinely use 180 fps in my GH5, and I think it looks pretty good. Obviously, I have to use a higher ISO, as the camera will lose sensitivity at higher frame rates -- that's true of any high frame rate camera, and not specific to the GH5. And 120 fps and 180 fps are limited to 1080p, but I understand that. (Maybe some slower frame rates are also limited to 1080p, but I almost always go to 180 fps when I want slow-motion video.)

So, am I missing something? Is there something about the 180 fps setting in the GH5 that produces flawed video?
 
It's a visual opinion. Like some people shoot 8K because they think anything less may look inferior.

The GH5's slow-motion is decent, but its processing is hindered. It does not provide the best quality it can (for obvious reasons like price and because it's a stills camera that shoots video). If you had access to other systems and saw the results side-by-side, you'd see that the 180fps is soft compared to other hardware's output.

On a technical note, usually the higher you increase the framerate, the worse the results are (noise - chroma - compression) unless the camera is specifically designed for high-speed.

With that said, if you think it looks good then that is all that matters.
 
You probably don't even need to compare its 180fps to another system's - just compare it to the GH5 at 24fps.

Part of the problem is the bitrate, no? There is no commensurate increase in the bitrate as the framerate increases, so you are storing less data per frame. (And probably doing a lower bit-depth readout of the sensor to boot.)

But I think the lower quality of the footage is probably most apparent if you're viewing it on large screens or doing big color correction adjustments such as lifting the shadows a lot.

I like to use the HD crop on my GH5 and S1 when I need to punch in and get a tighter shot while running and gunning. It is definitely softer than using the full sensor, but for what I use it for the sharpness is adequate and the functionality is extremely useful.
 
IMO, most cameras' 1080/120p stinks.

Ever see a Canon camera try slow-motion? lol

I'm not really convinced it's the bitrate (at least as the main factor) since the G2 shoots its 300fps at a lower rate and it looks better than most cameras at 120p.

https://www.youtube.com/watch?v=ZDj0VW9B5vA
 
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I'm having trouble finding data on the UMP G2 comparing all resolutions and bitrates.

But that 300fps is HD at 8:1.

My impression with BMD is that they maintain a constant amount of data per frame as you increase resolution and framerate. (As one should!)

Hmm it looks like 4.6k 8:1 @30fps is also 68MB/s. So that's 5.6x the pixels at 1/10 the the framerate. So the 300fps is using half the data per pixel by comparison. Is it only a 10-bit file?
 
Yeah I saw that but it doesn't comment on how the 300fps is recorded. But it says that HD 30fps 8:1 is 12MB/s, so that confirms that 300fps 68MB/s is about half what it would be for constant data/pixel. Dubious. But I agree the results are good.

I suppose that on the GH5 if you have the same bitrate for 24p as you do for 180p, you're reducing your data/pixel by a much greater ratio.
 
I downloaded a 300fps clip (original .braw) and I downloaded Resolve, but I can't figure out where the clip's bitrate is in the software.

Scanned every single window possible (at least I think I did), and I see all of the clip's properties (literally everything) besides the data rate.

I think the way people originally figured it out is by seeing how much space is left on a freshly formatted card while in the 300fps mode and compression setting.

[Maybe a Resolve guru would know more.]
 
I read on newsshooter that the higher framerates on the g2 use 12:1 - so maybe the bitrate is consistent with 12:1? In which case it's highly compressed but not below an accepted standard for other framerates on the camera?
 
ahalpert said:
I read on newsshooter that the higher framerates on the g2 use 12:1 - so maybe the bitrate is consistent with 12:1? In which case it's highly compressed but not below an accepted standard for other framerates on the camera?
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Uncompressed 1080p is about 3 gigabits per second (Gbps), so 3 Gbps divided by 12 equals 250 Mbps. That's definitely compressed, but MP4 1080p is routinely compressed to 24 Mbps and it looks pretty good. 250 Mbps for 1080p has a lot of breathing room compared to what we're used to on the GH5.
 
ProRes 422 HQ, an industry-standard benchmark, is 440 Mbps at 60fps in 1080p.

120fps would be 880 Mbps.

I don't know what the data rate is for 180fps in 1080p in the GH5, but I'd compare it to the above and see how much you're losing.

ProRes 422 HQ - or even ProRes 422 - is often regarded as the bare minimum camera data rates should be for their respective resolutions and framerates.
 
Also keep in mind the difference between MB and Mb. (Not really something I have to mention here, but it is easy to confuse in various nomenclature write-ups.)
 
BobKo said:
Uncompressed 1080p is about 3 gigabits per second (Gbps), so 3 Gbps divided by 12 equals 250 Mbps. That's definitely compressed, but MP4 1080p is routinely compressed to 24 Mbps and it looks pretty good. 250 Mbps for 1080p has a lot of breathing room compared to what we're used to on the GH5.
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Yikes - it looks like the bitrate for 180fps on the GH5 is 20Mbps - can that be the only bitrate available for shooting like that?

Yeah, the compressed formats on the GH5 look good, but you always lose something somewhere with compression (usually in the shadows and the fine details). Hair follicles always look really clear and distinct in Blackmagic camera footage (at least when they're recorded at low compression). They pop more than compressed formats.
 
ahalpert said:
Yikes - it looks like the bitrate for 180fps on the GH5 is 20Mbps - can that be the only bitrate available for shooting like that?

Yeah, the compressed formats on the GH5 look good, but you always lose something somewhere with compression (usually in the shadows and the fine details). Hair follicles always look really clear and distinct in Blackmagic camera footage (at least when they're recorded at low compression). They pop more than compressed formats.
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Just to crunch the numbers on some 180 fps video I shot with the GH5:

Windows 10 reports that the total file size is 220 MB (that's megabytes)
Windows also reports that the data rate is 30,340 kbps (that kilobits per second) That equals 30.34 megabits per second

Doing the arithmetic, 220 MB x 8 = 1,760,000,000 bits

1,760,000,000 bits divided by the number of playback seconds (58) = 30,345 kilobits per second (at a playback rate of 29.97 fps). That equals 30.35 megabits per second, which is essentially equal to what Windows reports.

Therefore, recording at 180 fps on the GH5 yields a visual file that is recorded at a bit more than 30 Mbps. I add "visual" because Windows also says that another 1,537 kbps is added onto that for audio, and (as far as I know) there is no audio with slo-mo on the GH5. And isn't 1,537 kbps uncompressed 48 kbps audio? Therefore, the total bit rate that Windows reports is 31,878 kbps, which is 31.878 Mbps.

Roughly 30 Mbps for 1080p is reasonably respectable. It doesn't approach uncompressed or even the various RAW, ProRes, DNX or even Motion-JPEG formats, but the GH5 will record presentable 1080p at 20 Mbps, so 30+ Mbps is a nice chunk of added headroom. A lot depends on the quality of the encoder, of course.
 
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Gotcha - so the recording codec must be 180mbps for 180fps and then the playback is a 30fps file at 30mbps. So you should expect the quality of the 180fps to be on par with shooting 24fps in a 24mbps bitrate.

Yeah, I think the 24mbps codec looks fine but you're better off shooting it with the look burned in. I have some data-conscious clients who request 24mbps and some who only want v-log at 200 or 400mbps (in 4k).

There's no doubt that the 400mbps all-intra codec will be more detailed. But again, the UMP G2 shoots its highest framerate at 12:1 compression only. Some people might be making too big of a deal of the quality difference above 120fps, especially since there will be relatively little change between frames so you should be able to compress it very effectively with the long-GOP codec that it uses.
 
On a side note, the actual .braw clip I downloaded said 3:1 compression, which confused me even more. Framerate was 300 in the software.
 
The main problem I've had with 180fps footage has been occasional moire, making some shots unusable. Other than that its shortcomings are for me an acceptable tradeoff for its strengths.
 
markoconnell said:
The main problem I've had with 180fps footage has been occasional moire, making some shots unusable. Other than that its shortcomings are for me an acceptable tradeoff for its strengths.
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Then they're line-skipping in the readout? A bigger issue than compression
 
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