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25p official topic, aka Don't cry for me Argentina
  • In this topic we'll collect all GH2 25p wishes and cries. :-)

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  • For those who might not have seen this before...



  • On the question of the need for 25p, I'm curious - is the problem of syncing to lamp flicker for mains-driven lamps no longer relevant?

    I was under the impression using 24p in a scene with 50Hz-driven-fluros, for example, (white balance issues aside) would produce some rather undesirable effects... and if we're going the GH2 route, I presume we're not all in situations with a large lighting budget. Yes, I'm aware of the 1/50th shutter trick, but that's a bit constrictive, particularly if you want a faster shutter / wider aperture combo for bokeh (I'm old school ;o) don't really like the term 'bokeh', but I'll admit it covers an aspect of DOF effects that didn't have its own name before).

    There's been plenty of comments that 25p is irrelevant because you can speed up 24p, which is well and good as long as you stay outdoors, but surely being unable to shoot under lights is an important limitation for any kind of video or movie work - unless someone is suggesting that shooting in the dark is just fine.

    If the GH2 or the PTool hack has fixed this issue somehow, please let me know - it would be awesome (if unexpected) news...
  • Yes, 1/50s shutter can only partially solve the problem. If you use more different cameras it could be a problem in PAL land... You usually cannot put together 24FPS and 25FPS footage without difficulties. Something won't work, either the picture or sound, even though you converted all 24p footage into 25p or vice versa.
  • That's the issue I face with using my GH2 with my 2 XHA1 camcorders hence run my GH2 at 1080i
  • I shoot multicam concerts and theatrical performances as well. That 4% speed up thing does not work if you have one 24p cam among a bunch of 25p/50i ones. They'll just get out of sync. There are decent motion detecting framerate conversion algorithms yet they're slow and expensive while still being a compromise. 24p is not quite a show stopper in a PAL multicam project with most of the material shot at 25p - you can work around it - but it is definitely a HUGE PITA and LOTS of wasted time. It's all about the convenience and speed of the workflow. I'm seriously considering getting one or two G3s because of that.
  • @zigizigi +1

    Aside from attempting to mix 24 and 25 footage, I am finding that the GH2 drifts out of sync in 1080 50i (much more than my Canons) so don't know what's going on there - but that caused me a lot of work the other day to mend a bunch of clips (60+) in a shoot which was being mimed to playback.

    Unfortunately I'd removed the audio from the timeline GH2 clips having done what I thought was an initial sync and then cut the clips up - so I had to match them up again one by one by syncing up the original takes and then matching my edited video clips to that (too much work already done to just start again). Won't make that mistake again - I'll keep all the audio with the gh2 clips but mute it all - so I have a sync reference to return to should I need it. Not something I've worried about for years with my XHA1s and other SD camcorders I have, which hold sync perfectly. I've now got pluraleyes, so am ready for my next shoot, but the GH2 shouldn't be drifting that much.

    That's without dealing with 24p!

    Of course I could ditch my Canons but they're great for lots of usability reasons (and have 25mbps cbr).
  • Why you can't use Cineform neoscene to convert 24p to 25p? It also converts 4:2:0 to 4:2:2 and have great firstlight colour grading... Sound streching is correct. I know 25p is 25p but this is small solution.

    mk
  • Not cries but just should point out (and rant) that 25p is used in a lot of countries...and sometimes ESSENTIAL for work.
    I currently conform from 24p and on occasion I get out of sync trouble. 50i is frankly shit on the gh2....soon as everyone abandons interlace format the better.

    So its so unreasonable to hope with the hack that 25p is a possibility? Seems it isnt taken very seriously but for some of us it is.
    Every bit as important as 4.2.2 mjpeg and hdmi output.

    wah wah wah ;-)

    I think the simple question that has not been answered...will we get 25p from the hack?
    When we get the answer to this then we can all shut up ;-)

  • I need a Cinema 25p for this reason I'm forced to shoot video with my dusty
    Canon HFS100 and it has Cinema mode, works without any problems ...
    Cinema 25p is "must have", phew Panasonic ...
  • +1 wah, wah, wah. You've started me off now!
  • I also find combining footage from GH2 and other PAL cameras the biggest hastle, especially explaining this for students.
    I think most people on this forum are aware of the workaraounds, but still, 25p will make the workflow much more streamlined (and for multicam it's essential). For many, this can be the difference for choosing GH2 vs another cam.

    Nice Downfall edit BTW ;) So, fingers crossed, I'm hoping for the best!
  • @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?
  • @stolpis100 That's the idea - even if the camera and mains phases drift slightly the brightness will only change very slowly (and could easily be compensated for in pp if it's an issue at all), as opposed to a distracting and practically impossible to remove strobe effect (especially if mixing lamps and sunlight).

    Everyone seems to be debating the relative merits of time-stretching, which I can understand to a point, but the big(-ger) issue is being locked to a single shutter speed when shooting under lights. I don't really understand why people are putting the emphasis there, unless they all shoot mostly outdoors and natural light...
  • 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?
  • Excellent response from Mimirsan. That's exactly how most of us in countries where 25p is essential, feel like.

    Yes 24p can be conformed, but it's fiddly and causes minor problems. These guys discussing shutter speeds, time-stretching etc just shows how it complicates things for us.

    We're not looking for a boost in bitrate or something that will enhance aesthetics...just to simply be able to shoot in what our countries require us to.

    So I'll be crying for Argentina until it happens

    More importantly, as Mimirsan asked; "...will we get 25p from the hack?"

    +2 wah wah wah :P
  • 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.
  • I am in total agreement with the above. I do a lot of music videos where sync is obviously vital. The least time consuming method would be to ask the artists to play to a version of the track that has been slowed down, shoot at 24 fps and then reinterpret the video to 25p in post so that the sync matches in my 25p timeline, but even then we are jumping through hoops and the artists would appear to be over caffeinated in their movements! Please dear god let 25p with no adverse lighting flicker be a possibility!
  • @Ptchaw I have just illustrated in my post above how the 24p to 25p workflow is insufficient with music videos.
  • ..and it's still an issue with a mix of 24/25 cameras.
  • @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.
  • @stolpis100 The difference in speed is so small it really isn't noticeable. You don't need to make them perform slower :P

    @evero I can sympathise with multi-cam users, though if you really wanted you could shoot on 24p on all cameras!

    I can't talk for other editing software, but for Premiere at least, the render engine is very efficient at conforming footage and it really doesn't add much to render times; its just taking the frames in the same way but at a different speed.
  • @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.
  • @madact Thanks for the explanation, been trying to get my head around those details for a while now. Fingers crossed for 25p soon!
  • @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 Surely that rolling shutter issue you mention will be evident on any frame rate when shooting under regular lights, and an inherent issue with the way the rolling shutter works and not a 25p specific issue? At what shutter speed does the brightness variance start to become noticeable (in a negative way).