@_gl Interesting. I can see why it would be a lot more noticeable for Frasier, being slowed down by 17%!

Did some more tests, I think how noticeable it is depends a lot on the song - Beck didn't show it much, but some electronic stuff did seemed a bit quicker to be fair.

@_gl Just curious, do you find it noticeable for dialogue?

My industry point was that people were saying they required 25p for use in broadcast, when conforming 24p is widespread in broadcast.

Just tried resampling Beck - Beercan using Soundtouch, which I understand uses the SOLA algorithm. I honestly didn't notice apart from with a direct comparison.

For non-music work, the difference would be even less noticeable.

@Ptchaw, see this is why I'm unsually irritable on the subject. Don't assume I don't know what I'm talking about. Just yesterday I tested it again by resampling a CD track - the resulting speedup (equivalent 24->25p) or slowdown (the other way) are totally unacceptable to me. It's the same pacing difference as I noticed between the US and UK versions of Frasier.

Let me turn the tables, why don't you try it. Take a music track (with a beat) you like and know, and speed it up to 104.2%, with whatever algorithm you have available.

As I said, not everyone will care and maybe you don't - but I do.

@_gl I know the pace is changing, but I think you really need to try it before you say it has an effect on the footage; I've never been able to tell the difference. You're only being shown 1 more frame per second. Colour grading and polarising filters 'distort reality'.

Again with audio, I really doubt you'd ever tell the difference, let alone would it be a 'disaster'. I don't know what algorithm editors use, but from experience it has not just been an issue of 'good enough', but indistinguishable from the true speed.

I'll repeat (loosely) what I sent to Ian_t:

1) audio resampling changes pitch - unacceptable in many cases (people sound older, or younger & the feel of music changes)

2) audio stretching _without affecting pitch_ is not flawless - cheap algorithms are terrible, better ones like DIRAC3 (eg. in Wavelab 7) are passable but still have artifacts, and are very slow to process. It won't matter to everyone, it matters to me.

3) even if audio could be perfectly stretched, you are still changing the timing/pacing of the audio and video. For example, actors are now talking faster, music has a faster beat.

All of this distorts reality, and my artistic choices. It won't matter too much for some shots, it's a disaster for others - if you care.

Lots of video people care more about visuals than audio (that's why you still often see bad lip syncing in music videos). I care about both. So just because it doesn't seem important to you, don't assume that's true for everyone. I could also say 'why bother with higher bitrate, isn't the GH2's 24mbps already good enough'? It is for some - but if you really care about quality, you want more. Case closed.

@madact You are right, though there are a couple of things I'd like to add:

You can't quite use any shutter speed you'd like due to rolling shutter; on high shutter speeds the time the top of the image was captured will be earlier that the time at the bottom of the image, so the brightness will vary across the frame.

You are limited to a shutter speed of 1/50th at 24p (and very slow shutter speeds) for lighting, though there isn't really a reason for not using 1/50th at 24p.

@Ptchaw "You'd get the same problems with lighting and shutter speed at any other frame rate, nothing to do with conforming. The shutter is still open for the same amount of time for each frame."

Not quite sure what you mean by this? I agree that it has nothing to do with framerate conforming, but the comments about "any other frame rate" and "open for the same amount of time" don't seem to make sense. I'm not sure you're disagreeing, but I'll give the lecture for the benefit of all ;o)

The problem is that if you have 50Hz mains, the light output from incandescents and particularly fluros has a ripple at 100Hz, though some have an asymmetric response (or in one case I saw, a bridge-type dimmer circuit with one side burnt out :oS) which gives a waveform that repeats at 50Hz. If you run a fast shutter speed and the frame rate is not 25 or 50 fps, you hit that ripple at a different point each frame, and hence get a different amount of illumination on the scene each frame, hence the flicker. If you set your shutter speed to *exactly* 1/25, 1/50, or if you're really lucky (depending on the specifics of the lighting) 1/100 of a second, you get *exactly* a full cycle of the ripple in each frame, which averages out to no flicker. Any other shutter speed, and the whole thing strobes at either 2 or 4 Hz, depending (once again) on the specifics of the lighting.

However... and this is why it matters: if your shutter fires 25 (or 50) times a second, you can use any shutter speed you like, because it will always 'open' at the same point in the ripple and 'close' at the same point in the ripple.

So the general rule is, if you're shooting under domestic / low budget lights with detectable ripple, you match your *shutter* frame rate (i.e. the rate at which images are physically taken at the business end of the camera) to whatever frequency is running the lights. Or get limited to a couple of set (and relatively slow) shutter speeds... which can suck, esp. if you want a bit of control over motion blur.

Note: A lot of stage lighting and big-*** quartz floods don't really suffer from this as the thermal mass of the filament takes the ripple out pretty well, and DC or HF LED arrays have no issues at all, but any domestic globe, fluro, or mains-drive HID lamp will do it.

@ptchaw For many of us, using the GH2 as B cam is very likely. I use it with AF100, but in the future also in other multicam settings with various PAL cameras (with the 30 min (pal) timelimit gone, it's very usable for this).
Time stretching and pitch correcting huge projects will add even more rendering time, and believe me, I struggle enough with time and power consuming timeline issues as it is.
In some projects you have the time, in some you don't.

@Ptchaw I have just illustrated in my post above how the 24p to 25p workflow is insufficient with music videos.

Moving all conforming discussion here...

@_gl @mrbill Please give me a scenario, other than maybe B-cam, where conformed 24p is insufficient, now that we've established it is widespread in industry and produces indistinguishable results.

Time stretching and pitch correcting in Premiere is as easy as speeding up by 4.2% and checking the preserve audio pitch box.

@Donnie88 @madact You'd get the same problems with lighting and shutter speed at any other frame rate, nothing to do with conforming. The shutter is still open for the same amount of time for each frame.

@evero If you're thinking of the 180 shutter rule, the difference between 1/48th and 1/50th shutter speeds is indistinguishable.

Not saying that 25p/50p isn't needed on the GH2, but this is a perfectly usable workaround.

edit: @madact answered the question. But I wouldn't think 25p would solve all those problems? Would more of the shutter settings be compatible with 50Hz lighting when using 25p vs 24p?

@evero correct. 25p is vital for me working in London and the lack of it if the only reason I have not dived in and purchased one. I work 99% in post so am no expert in actual shooting so have one question...Am I right in thinking if 25p is achieved on this camera then you could shoot under our 50Hz lights at any shutter setting of our choosing?