Personal View site logo
Make sure to join PV on Telegram or Facebook! Perfect to keep up with community on your smartphone.
GH4 Firmware 2.3, V-log for $99, Epic Panasonic marketing fail
  • 1451 Replies sorted by
  • LPowellLPowell

    ISO was orginally defined objectively as film speed. Nowadays, it's just a number that camera manufacturers manipulate to make the various camera modes appear to work in a familiar manner to consumers. Different sensors have a wide range of sensel pitches and well capacities, and have widely varying sensitivity to light. But they're all pretty much linear and with decent optics, each can handle bright daylight. In a fixed lens camera, the maximum output level of the sensor is scaled to produce enough overexposure to fully blow out the JPEG or H.264 encoder at whatever number the manufactor selects as the "minimum ISO" (typically 100, 200, or 400). At the opposite end of the ISO range, what counts is how high you can boost the ISO setting before the image gets too noisy, which is specific to each image sensor. At base, it's all relative to the highlight clipping level of the sensor, regardless of how you manipulate the tone curve and its exposure gain. Dynamic range extends downward from that highlight clipping point, until you run out of enough photon sensitivity or bit depth to discriminate anything useful but black.

    With the GH4 in V-Log-L mode, highlight exposure at ISO 400 is scaled at the same level as highlight exposure in Cine-D at ISO 200. That is why the noise levels in both profiles are pretty much the same.

  • balazerbalazer

    @Tjabo, sorry, I should have explained how that video was created. I asked Mckinise to shoot it for me, holding the exposure constant while ramping the ISO from 400 to 6400 in third stop intervals. In the YouTube video I ran his ramp twice. In the first time, the bottom half is V-Log L without any transformation, and the top half has exposure compensation applied to compensate for the changing ISO setting, and Rec.709 rendering. The second time is just like the top half of the first time. The noise is most apparent in the dark area above the keyboard. What I wanted you to see is how the noise is virtually unchanged (when exposure compensation is applied) even as the ISO is changed from 400 to 6400. YouTube has turned that noise from grain into overcompressed mush, but that doesn't alter the conclusion: the ISO setting has very little impact on the noise. It's a counter-intuitive conclusion. All our experience has taught us that ISO 6400 must have a lot more noise than ISO 400. But it's only because when you increase the ISO setting, you're usually doing it to compensate for a low exposure. A low exposure is the source of most of the noise, not the higher ISO setting. When you hold the exposure constant, increasing the ISO setting doesn't increase the noise much at all. (at least not until you get to really high ISO settings, and then sensor noise starts to be a bigger factor) It's because shot noise is the largest contributor to overall noise at low and medium ISO settings. Shot noise is inherent to the light of the image falling on the sensor. (and compounded by the sensor's fill factor, quantum efficiency, and colored filter losses) Changing camera settings doesn't change the shot noise. Changing the exposure (shutter speed, aperture, lighting) does change the shot noise.

  • VeskuVesku

    In practice we must increase iso because we have not enough light to use low iso. Then we have more noise. If we overexpose heavily high iso we get less noise but loose highlight detail. Is it a compromise between noise/dynamic range. If I under expose at iso 200 and adjust image to normal I get good dyn range but more noise in shadows. It is like using iso200 for highlights and iso1600 for shadows at the same time.

  • TjaboTjabo

    Thanks @balazer!

    @Vesku, I guess looking at the test video above from blazer, it appears that in the scenario you describe, maybe we just need to raise the ISO even more to reduce some of the noise. I think that is the point balazer is making. No?

  • VeskuVesku

    I think the lesson is to get as much light as possible to sensor to have less "shot noise". If the "shot noise" is always the same why not underexpose with low iso and get better dynamic range.

  • caveportcaveport

    I'm not sure what 'shot noise' is. Nearly all noise is the inherent sensor noise and maximising the amount of light hitting the sensor will ensure that the signal to noise ratio is maximised. In electronic cameras, ISO is an electronic gain (after the sensor) which will increase the signal AND the residual sensor noise. Most cameras have built in noise reduction which is optimised for that particular camera. Using gain adjustment in post production will lift the noise as well as the signal, but without the manufacturers noise reduction. This is usually a noisier result than using an appropriate ISO and optimum exposure in camera. Under-exposing and lifting gain in post, is usually the noisiest option and does not increase dynamic range. The best dynamic range is with optimum exposure.

    With the GH4 I find the best (lowest noise) results are by using an appropriate ISO for the available light conditions and exposing to maintain clean highlights. Also being careful with white balance is important to noise visibility due to the 8bit 4:2:0 H264 codec. The colour channels are fairly low resolution and if the white balance is pushed a lot in post-production, the image can start getting VERY noisey.

  • balazerbalazer

    https://en.wikipedia.org/wiki/Shot_noise

    At low ISO settings, shot noise dominates over sensor readout noise.

  • mattherematthere

    Some interesting discussion on the creator's blog:
    http://www.60fotogramas.com/gh4-mejor-configuracion-en-v-log-y-una-alternativa-el-leeming-lut/

    google translate gives a good translation.

  • TjaboTjabo

    Thanks for that! Good video, and that guy has some other good stuff too.

  • belfrymanbelfryman

    I'm seeing stacks of banding on the wall myself, fine if you just look at the woman's face. Is that just me?

  • mattherematthere

    @belfryman you are right, but here the focus of the video is to show that a lot of people avoid high ISO and end up under exposing which is often worse (for noise) than raising ISO.

    There is some additional discussion on the blog, regarding the banding, which can be "minimised" by adding a small amount (5%) of Film Convert grain (not used on this footage).

  • belfrymanbelfryman

    Yep, saw that one, didn't help much. But it is interesting how you're not really losing anything pumping the ISO.

  • MikeLinnMikeLinn

  • aaronchicagoaaronchicago

    New video that I shot primarily with V Log L. Everything except the rooftop shots are the GH4.

  • TjaboTjabo

    @aaronchicago, I think you nailed that!! Phenomenal shooting and editing. Not to mention, the GH4 seems to do what looks to me like a really professional job now. Of course it't not perfect, but what is.

    What did you use to shoot the rooftop stuff, A7s?

  • Iban_CorominasIban_Corominas

    @aaronchicago Great work! It looks fantastic, did you use 48fps on the car shot??

  • aaronchicagoaaronchicago

    @Tjabo @Iban_Corominas Thanks! I shot the rooftop stuff with C100 MkII. The car slow motion shots were 60fps slowed 40% to 24p.

  • GardnerGardner

    @balazer What settings would you recommend for Sharpness and NR for GammaLite in Camera?

  • balazerbalazer

    @Gardner, sharpness and noise reduction settings are totally up to you, since they have no effect on color. Some GH4 users may have a recommendation.

  • GardnerGardner

    @balazer Thank you. One more question -- How would you compare your LUT to the Leeming LUT?

  • balazerbalazer

    @Gardner, a typical display LUT is designed for footage shot with a certain exposure and proper white balance. Those LUTs don't facilitate basic color correction. My LUTs are designed to enable white balance correction, exposure compensation, and contrast adjustment in the intermediate color space. That's the main difference. Beyond that I can't say much about the Leeming LUT because I haven't tried it. I'm sure it's fine. It's just a very different approach.

  • GardnerGardner

    @balazer Thank you for answering my questions and I look forward to using your LUT for my projects next year!

  • HillTop1HillTop1

    @aaronchicago, that video is badass. The GH4 shine there very well. Great work, thanks for sharing.

  • TjaboTjabo

    @aaronchicago, thanks!

    For anyone, what is GammaLite @Gardner mentioned above?

  • balazerbalazer

    gammaLite is my gamma-encoded color space for color correction of GH4 footage in Adobe Premiere. I also have a log-encoded color space for DaVinci Resolve, FCPX, and Sony Vegas Pro.

Add a Comment