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GH2 Flow Motion v2 - 100Mbps Fast Action Performance & Reliability for Class 10 SD cards
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  • I shot the following footage with my GH2 with FlowMotion 2.0, using a Voigtlander f0.95 25mm lens. Because I was conducting the interview, there are some technical issues since I didn't have a dedicated camera person. For example, there are some gaps in the video, since I recorded sound separately. I'm releasing this under a Creative Commons license for reuse.

    I am shooting a documentary on the topic of "Heaven", interviewing people in four different countries (so far) and several different religious traditions, and Rabbi Raskin is the first person I interviewed from the Jewish faith. I learned some amazing things I never knew before about Judaism.

  • @LPowell Lee, I finally bought a second camera so I can test settings without flashing the camera sitting in the middle of a corn field. I'm not going to compare FM2.1 to other settings here other than say there is a lot of frigging genius on this site.

    I'm finished looking at night pictures. FM2.1 is wonderful at night and very low noise, high detail and the bitrates have been around 16. It works fine on a 32 gig 45 mb Sandisk but will not span (Neither will the other one I've tested).

    Since I do a lot of recording around water, the ability to handle running water, especially in 720p-60 is a major concern. FM2.1 is the only one that I've tried that doesn't lock up on a regular basis and still give maximum detail.

    This evening I have to cover a bicycle race and that will give me a chance to work on heavy motion although I still haven't figured out how to juggle two cameras during a race.

    This s a very good patch...Thanks!

  • @jrd Often high contrast scenes demand wide dynamic range. There isn't enough room to wiggle. Often highlight or shadow detail is lost. Getting intended details at acceptable image quality is the goal. Usually ETTR applies to linear format RAW data, not log format avchd frame or jpeg data. If I can get enough detail without ETTR, I wouldn't apply ETTR. Camera's EV reading is just reference. Gotta use it with the histogram.

    Ummm.... this is off-the-topic... so I would stop talking about this here.

  • @peternap thanks glad you enjoyed it. and yes he's absolutely pissed!

  • @weomck Great video and boy that bird looks pissed!

  • @stonebat

    I wonder. I tested it with a very high contrast scene, using FM2. One "correct" exposure, according to the histogram. One pushed a fair amount to the right, and a third, further to right, and allowing a small amount of clipping.

    It was no contest: the one pushed furthest to the right was the best one, from the POV of color correction and detail in the shadows. OTOH, bringing up the shadows on the "correctly" exposed clip turned the blacks milky.

    @luxis

    Yes, blown highlights are gone forever. However, small areas of clipping can be acceptable, depending on what's clipping. Faces no, but background detail, why not, if the overall image is more correctable.

  • @jrd ETTR applies only to RAW file. But there's one thing about GH2. Often its EV reading goes underexposed on high contrast scenes.

  • Here's a Hummingbird shot with Flowmotion v2.0 EX-HBR GH2 + Panny 100-300mm @ 150mm ISO 160, f/5.6, 1/60 sec. ......slowed to 1/4 speed, cropped to 720, added saturation to greens, reds, and a little to yellows in AE. Enjoy...

  • @jrd @karl I think this is unanswered question... I tend to prefer correct exposures myself and find it easier to work with later. Also believe that blown highlights are gone forever in digital realm. Was there a whole thread dedicated to this topic? of course is interesting to know how about FM2?

  • @jrd: I have made a different experience. I got the most pleasant results with correctly exposed pictures, with only saturation lifted a little and white balance corrected in post production.

  • Thank YOU Lee for the patches, ISO was auto so the camera took care of the exposure but I locked it before pressing record. Yes had to luminate the red and yellow channels as there was no sun-light, very dark gray day, there is a touch of diffusion added as well. That's not the final grading however, I want to enhance the stormy look of the day.

  • @LPowell

    A little off-topic, but per your question on rambo's exposures -- I'm finding that with FM (but really, all patches/setting with the GH2) it's always better to expose to the right, even into slight clipping, and then bring mids and lows down in post. The files are slightly larger than when "correctly" exposed, and (more importantly) more correctable.

    Is there any consensus on this question -- at least for uncontrolled lighting conditions?

  • @Rambo Your outdoor exposures look beautiful! Any color correction on the sample clip?

  • Agree that you really have to look at the flow of images for IQ--you can't really see how noise behaves in a static shot. The classic example of this is pulsing--which I find really annoying. You would not see it on a still, but once the movie starts, it is really noticeable.

  • @Lpowell,Thanks, I will do it on that way.

  • Part of a Project I'm working on. FlowMotion 720p 50, 1/100, converted to 25p slowed down 50%, 14-140 kit lens. Shot from the back of a Jetski.

    Best viewing the downloaded file.

  • @Lpowell, thanks. I didn't mean to imply any competition or that either patch was better or worse. I think they are both great and are mostly after the same goals, just going about it differently. And this is why I asked my question, simply to understand the inner workings of your patch and why things look the way they do, because I didn't know. Maybe it's my eyes or monitors but those dark blocky areas really stand out to me.

  • @svart The quantization tables used in Sedna are designed for an Intra-only encoder. They employ overkill techniques to record as much high-detail image data as possible, regardless of how perceptible the finest details may be in practice. As a result, Sedna records a large amount of sensor noise, as well as genuine image details, and to do so at high quality requires very high bitrates. At conservative ISO and medium and high illumination levels, sensor noise is virtually imperceptible, but in areas of very low exposure, sensor noise becomes significant. As with dithering, a layer of noise can conceal underlying digital artifacts in a way that appears to improve shadow depth.

    To my eyes, sensor noise looks much better in still frames than it does in low-fps video. I find random patterns of swirling noise to be distracting rather than enhancing. With Flow Motion v2, I've specifically prioritized continuous motion picture quality over static still-frame image quality. I want to see frames that integrate smoothly over time, and for that purpose, I don't want the encoder to preserve myriads of randomly varying statistical details.

    This, by the way, is why I favor Flow Motion's 3-frame GOP over Intra patches. As animators have found, the most fluid motion picture effect is achieved when one or two tweened frames are inserted between each keyframe in a video sequence. In FM2's case, the pair of B-frames that follow each I-frame are actually reconstructed using a technique similar to animation tweening. Inter-frame macroblocks in a B-frame are made of an averaged combination of motion vectors taken from both preceding and following I-frames. These tweened motion vectors are then refined with a layer of residual details extracted from the original source frame. This methodology insures a high degree of inherent frame-to-frame continuity.

    With an Intra patch, each frame is recorded as a separate individual keyframe, technically uncorrelated to adjacent frames. In this case, motion picture continuity is produced by recording each frame with enough static image quality to independently preserve all details common to each sequential frame. With extremely fine levels of quantization, random discrepancies between frames (which would enhance the detail of a still image) introduce sporadically varying details that I find distracting. In my view, optimal motion picture quality is produced by careful control of image detail rather than wholesale maximization of bitrate.

  • @ Lpowell, maybe I asked my question incorrectly. I'll try a simpler version of the question. Why do the dark areas in Flowmotion not look like Sedna in this post: http://www.personal-view.com/talks/discussion/comment/66160#Comment_66160

    I understand I probably used the term "macroblocking" incorrectly and I understand the way the encoder works, what I do not understand is if Flowmotion is doing things equally or better than another patch, I.E., "a GOP1 patch needing 2xxmb/s to equal Flowmotion's capability", then why are the dark areas much more blocky? Wouldn't imposing a low side limit to bitrate, to keep the bitrate from going too low, and trick the encoder to break those areas up better?

  • @svart Flow Motion v2 is not bitrate-limited in low-light conditions - it will use as much bitrate as it needs to encode the video at its finest quantization quality. If you use Stream Parser to examine the DC QP level used in each frame, you'll see that FM2 maintains a uniform DC quantization of 5 at even the lowest levels of illumination. (Levels of quantization below 5 rapidly reach diminishing returns without perceptibly improving image quality.)

    I'm not sure what you're referring to as "macroblocking", as the AVCHD encoder's inherently coarse sampling of dark shades can produce blotchy shadow effects regardless of how finely the macroblocks are quantized. Flow Motion v2 is designed to suppress high-detail chroma noise while enhancing luminance details. Since shadow areas usually have very low-contrast luminance details, they will turn out more contoured rather than noisy in FM2.

    I lifted the shadow details in the Flow Motion v2 24H frame grab above, and graded it to reduce the saturation in the shadows while maintaining balanced color tones in the mids and highlights. (Yellow flowers are excellent test subjects for this purpose, as the gradients on their pedals are very sensitive to red/green color balance.) Bear in mind that the highlights in the video were intentionally recorded two-stops underexposed, as a test of low-light performance. This type of shadow grading requires very fine adjustments of individual RGB gain, gamma, and pedestal controls.

    image

    Low Light FM2 Shadow Details.jpg
    1024 x 540 - 235K
  • I haven't had time to test this patch yet, but I'd like to. The only problem I've seen in the pics so far is the macroblocking in the shadows. How far down does the bitrate drop in low detail/light situations? I think the GOP1 patches generally keep shadows better due to their near constant bitrates. Could we impose a lower limit in this patch to keep low detail areas from macroblocking?

  • @LPowell I can't upload now Lee (Storms again) but maybe you can shed some light on this. In both 24p and 720p I get great, almost noise free video at night.

    The other day when videoing under a shelter (no sides) I got a disturbing amount using a 2.8 lens and ISO 200. 720-60, bright light outside and shaded in, shutter 1/125, I don't remember the fstop, smooth -2. This was showing up mostly in the Green.

    Any ideas?

    Aside from that I swear this patch is magic in 720.

  • @cubrun If you would like to have lower bitrates in 1080i and 720p modes, I'd recommend using the FH and H video modes. These modes are designed to limit their peak bitrates to less than 60Mbps, but will otherwise work exactly like the 100Mbps FSH and SH modes. You can also adjust the FH/H peak bitrate in PTool to your own preference, without disturbing the 100Mbps FSH/SH settings.

  • @cubrun I'm not an expert, but from everything I gathered here and there you can't just change the bitrate and expect everything to work fine. The AVCHD modes and parameters have some tight connections that will make it break if you operate large changes on single parameters without adjust almost everything else accordingly. What you are proposing is like driving a Ferrari at 60mph, it will run but doesn't make any sense to do it.

    If you want extreme efficiency, you need to go with a long GOP setting like Sanity as it's performance/cost ratio is pretty much unrivalled. I find it's pretty good overall but some people will run away from long GOP settings like the plague.

  • Maybe a stupid question. Does it make sense to reduce the video bitrate on the Flow Motion patch v2.01 for FSH / SH at 32000000. I mostly shoot weddings, at 99000000 the sd card has been filled up too fast.

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