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GH4 Firmware 2.3, V-log for $99, Epic Panasonic marketing fail
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  • aaronchicagoaaronchicago

    I have absolutely no idea what any of this means but if someone figures out a good way to interpret the footage in Premiere i'll be grateful.

  • rNeilrNeil

    @joonas_t

    Some of it's "fairly simple".

    A gamut is a matrix or "set" of defined colors. There's quite a few different gamuts out there, and you can google your heart away on it. sRGB is one, AdobeRGB is somewhat similar but "bigger", in other words with a wider range of colors ... most computer monitors have trouble showing all the colors in AdobeRGB let alone anything wider. Full broadcast monitors (think Flanders) are expensive because they are actually designed to accurately show a LOT wider range of discrete colors.

    Any sensor/image-processor combination (in your camera) produces images for a specific gamut (again, defined range of discrete colors) with a specific way to encode data from the camera to the digital file according to the rules for the gamut it is designed to use. Most cameras that are non-log and non-raw shoot straight sRGB. Or a camera-makers in-house variant that still "lives" by the rules for general color-encoding for sRGB. LOG and RAW cameras may shoot sRGB ... but probably in LOG or RAW mode shoot a specific modification or different gamut.

    Editing programs on the computer have their own specific gamuts they "work" in, and this is an area of great argument as to which is right, which is wrong, who's stupid, who's brilliant, and who's irrelevant.

    But they are all designed to "read" the gamut of the camera files, apply corrections to it, and output that into a display-space gamut for the computer monitor or tv-broadcast monitor, and to whichever gamut is specified internally by the chosen output codec.

    So ... normally you the user need pay no attention to gamut. Your devices do. If you're a picky sot pro editor, you'll be very capable of arguing this forEVER. I've been around such arguments at NAB ... and the worst are when editors & colorists get together and someone flames someone else's "darling" program/camera/gamut whatever over improper color handling.

    Which is where the ACES thing that balazar mentioned comes from ... a number of people in the pro community trying to get a real, sensible set of standards for handling digital image files from the camera to display that are 1) well thought out 2) well implemented and 3) comprehensive. It's a work in progress. With a LOT of arguing.

    The similar word "gamma" is easiest to think of as the center of the image data ... the middiest midtone. Move that up to be a bit brighter (stretching the shadows up and squishing the highlights together a bit) or down a bit darker (squishing shadow values a bit while stretching highlight values). This is primarily a 'luma' term, in effect: the brightness of the midtone value.

    LOG footage is encoded a bit differently in most cameras than "regular" codecs, in that the luma values are stripped totally away from the color values and recorded in one manner, and the data to re-create the color values from that are included in the file. (Not exactly "technically" correct, but works to be getting on with.) The way the math works on this, you can encode a lot more dynamic range in the same amount of "bandwidth", and still re-create the color data in spades in post.

    The basic "tool" for returning LOG encoded footage into "standard" images is ... the Look Up Table, a matrix of data-combos commonly referred to as a "LUT". LUT's designed to do LOG de-encoding (my word!) typically sort the Luma values back to where they "should" be, then take the Luma values and mix them with the chroma values that were stored, and give you your color back. For this, the luma needs doing first.

    Every flipping camera maker creates their own special flavor of LOG ... which is why people have tried using say Arri LOG or the Panasonic Varicam LOG ... to see which "fits" or works with the new GH4 version of LOG best. Sadly, Panny should have either stuck to some "known" LOG format ... or provided a proper LOG de-encoding LUT for the GH4.

    Instead, they apparently wanted to make it sorta like the "Varicam" log they have in an in-house big brother video camera ... but either they just failed or technically it can't be the same (probably the latter, in my opinion). So ... it's sorta like the Varicam LOG but not really ... and HOW you convert LOG footage to "normal" is rather important. Especially with files with as few data-bits as a GH4 has compared to the more spendy rigs out there.

    Hence the troubles that have ensued ... the arguments/postulation of differing causes/fixes ... and troubles getting the stuff processed "pretty" right off the bat.

    Asleep yet?

  • balazerbalazer

    Big thanks to @mash and @Mckinise, who provided me with a bunch of V-Log L footage.

    GH4 V-Log L Measurements

    • V-Log L maps middle grey 2/3 of a stop lower than Standard does at the same ISO setting. To be consistent with Standard, ISO 400 in V-Log L should have been called ISO 250. (I measured 0.64 stops difference)

    • In V-Log L, the camera's built-in exposure meter reads 2/3 of a stop higher than it does for Standard if you want middle grey mapped the same way. When the meter reads +0.0, it should say -0.7. (confirmed in firmware v2.3)

    • V-Log L has 1 and 1/3 stops more highlight range than Standard photo style at the same ISO setting. (measured 1.30 stops)

    GH4 V-Log L Exposure Guide

    • Set the photo stye to Standard. Using an ISO setting of 250 or higher, adjust the ISO and the exposure until the image looks well exposed. Then increase the ISO by 2/3 of a stop and switch to V-Log L, keeping the same exposure. This will roughly match the middle grey levels between V-Log L and Standard. V-Log L will have 2/3 of a stop more highlight range.

    • If you use the camera's built-in exposure meter in V-Log L, aim for an exposure reading of +0.7.

    • At low and medium ISO settings, shot noise dominates over read noise. Therefore the exposure is the most important factor in determining the overall noise level (much more important than the ISO setting). To minimize noise, strive to maximize the exposure, reducing the ISO setting and/or overexposing as necessary while still trying to maintain any highlights that you don't want clipped.

    • If your post workflow supports exposure compensation, you can overexpose the shot and compensate in post to further reduce noise. Expose 1 stop higher than you would in Standard to match its noise performance. Expose 1 and 1/3 stops higher than you would in Standard to match its highlight range.

    • These guidelines apply whether you are referring to the Varicam V-Log/V-gamut manual, or using the Panasonic V-Log ACES IDT, or using the V-Log-to-709 LUT. They all map middle grey in approximately the same way.

    GH4 V-Log L Assessment

    • The gamut matches V-Gamut quite well. Color accuracy looks good (precision issues aside), and is much better than Standard. Standard is a lot less standard than I thought, doing some unexpected things to color saturation.

    • The optoelectronic transfer function matches V-Log somewhat well. There are noticeable deviations: blacks are too low; other points on the curve are too high. In practice it won't be a big problem.

    • V-Log L in 8-bits lacks precision, which is particularly evident in the color difference channels. Expect to see pink, green, purple, and yellow splotches and banding in low saturation parts of your images. 10-bit recording should fix that.

    • Panasonic made the base exposure index 400, which is a bizarre choice. It effectively pushes all levels down, leaving one third of the V-Log curve unused and exacerbating the color precision problem over a larger range of shadow values. There's absolutely no reason Panasonic couldn't have set the base exposure index higher and utilized a greater portion of the V-Log curve, at least at ISO settings above the minimum. It shows that the Panasonic engineers don't really understand log color spaces.

    • Recorded videos have the video_full_range_flag set, just like a standard photo style recording made with a luma setting of 0-255. That's not how V-Log is specified in the Varicam V-Log/V-Gamut manual. V-Log specifies Rec.709 ranges, with 0% RGB using a code value of 64 and 100% RGB using a code value of 940. The difference is largely academic, especially in V-Log, which doesn't saturate the color difference channels. But it's another example of Panasonic engineers failing to understand what they were doing.

    • The Panasonic V-Log-to-709 LUT maps from V-Gamut correctly and maps middle grey correctly, but renders images with low contrast compared to a straight Rec.709 rendering. It is suggested only for previewing or as a starting point for grading.

    Personally, I think Panasonic really screwed up in making V-Log L. They missed an opportunity to make a log camera space that would work well for the majority of its users. As it stands, the quality of 8-bit recording is severely compromised.

    V-Log L ACES exposure test video:

    V-Log L ACES exposure test video:

    V-Log L ACES ISO test video:

    V-Log L vs Standard ACES test video:

    I have posted my Sony Vegas Pro OpenColorIO configuration with the V-Log color space used in all of these tests: http://www.jbalazer.com/aces-in-sony-vegas

  • BrumbazzBrumbazz

    @rNeil: thanks for the explanation

  • bleach551bleach551

    Trees and leaves yet again. GH4 VLOG-L 8-bit internal shot with Voigtlander 42.5 f0.95 @ 2.5 and Olympus 75mm f1.8 @ 3.5. Graded with Avid Media Composer with no Luts.

  • jopereirajopereira

    @balazer

    @rNeil

    Nice info.

    In theory, I understand what's going on... but shouldn't Panasonic know that? Could be that V-Log works very well in 10 bit but when Panasonic asks for $100 omits the fact we have to forget about internal (8 bit) recording, one of the biggest advantages of this camera?

    The fact is: when compared side by side, V-Log colors (using Panasonic LUT) are incredible, Natural profile colors are great if you don't have something better to compare to...

    The rest, it's pure misery... high noise levels and splotches all over the image.

    Do I have to create (how?) a LUT for Natural that mimics V-Log colors?

  • mattherematthere

    Thanks for the helpful discussion folks..

    I am confused too..

    Why would Panasonic not understand that mapping data across a narrow range is going to have a heavy impact on the 8bit image? Maybe they do know but don't care? That would seem odd because most of their users record internally to 8bit. Maybe it is capped for a reason (encoder limitations etc)?

    There are some reports that the DVX200 got an update to their v log version (that effectively increased saturation).

    Maybe it would be a good idea to indicate to Panasonic what updates to v log (or alternative log versions for testing) would be helpful for GH4 users?

  • lmackreathlmackreath

    I wonder when the likes of filmconvert /impulz will release updated profiles and LUTs for vlog...

  • Manu4VendettaManu4Vendetta

  • Manu4VendettaManu4Vendetta

  • balazerbalazer

    Do I have to create (how?) a LUT for Natural that mimics V-Log colors?

    That's actually possible. How easy or hard it is depends on weird or standard Natural's color encoding is. I tried the same thing for Standard, and it turned out to not be easy because of the weird things Standard is doing. Maybe I should try again with Natural.

  • tedramasolatedramasola

    I suggest you try getting Cine-D to look like V-log as it would be a flatter starting point than Natural profile.

  • Dr_JonDr_Jon

    So is V-Log as big a let-down as VW's diesel engine management system? Surely it wouldn't have caused them too big a problem to use the whole 8-bits for data? (Yes, I'm getting a bit fed up with posterisation effects in the sky...)

  • oscillianoscillian

    That Out and About video is incredible! Love the colors:-)

  • nobbystylusnobbystylus

    Ok - so got my official V-Log upgrade from panasonic. No more 'custom' for me. Histogram now seems to work as before at the highlights, but blacks seem to still clip somewhere before the left edge of the box. mmm odd..

    Also - Zebras - shall I set this to 100% ? It seems that 80% is still 'overexposed' for V-Log with my quick tests.

  • TronTron

    @nobbystylus I've got zebras at 70%, seems to be working OK there.

  • Manu4VendettaManu4Vendetta

  • joonas_tjoonas_t

    The video @Manu4Vendetta posted done by Maxwell Miranda is done with an 8bit codec. I can't really spot any major macro blocking in the footage... He graded the footage in FCPX and this is the method he used: "Yes my advice over expose while shooting and while grading use a log lut of your choice with 50% opacity and adjust your highlights up first bring your shadows down so the just hit 25% luminance and do the rest of the grade with midtones. Seems weird but I'm enjoying to control of contrast and roll off on both ends when I go that route."

    Why is the footage so "clean"

    the test footage I and others have taken has often been indoors and low ligth... Might outside and high quality ligth be a factor. Or is FCPX just suited for v-log 8bit?

    Here is the video again:

  • shianshian

    skies are a mess, but I'm assuming they'll always be

  • shianshian

    Anybody remember this thread for the GH1 and GH2 -

    http://www.personal-view.com/talks/discussion/2663/purple-filter-can-improve-image-on-gh1gh2..-project-blue-light/p1

    I put a minus green gel in front of my sensor on one of my GH2s and it made a huge difference in macro blocking and noise. I might just try it on the 4 and see what happens.

  • tedbrahtedbrah

    I've been testing and doing some math and V-log doesn't record even close to 8-bits of data which would explain the banding and macroblocking. Every profile on the GH4 records 256 luminance values which equals out to 8-bits(Since 32 values in a bit and 8-bits*32 Luminance values per bit=256 Luminance values total) but V-log L records blacks at a value of 30 and whites at 190. Now to change that to bits: 190(Highest value)-30(Lowest value)= 160 Total values in the V-log image. 160 Total luminance values/32 Luma values per bit=5-Bits. So when you record in V-log you're actually only capturing 5-bits of data. For color you're capturing 256 different color values per channel (256 Red, 256 Green, and 256 Blue values) but in V-log with 5-bits of data you're only getting 2(Black and white)^5-Bits=32 different colors per channel. The only reason Panasonic is doing this is because they want V-log in the GH4 to match the same bright and low values of 30(black) and 190(white) as the 12-bit Varicam 35. Why didn't Panasonic just optimize V-log for the 8-bit GH4? It would've be EPIC!

  • estarkey7estarkey7

    @joonas_t But the Iban Corominas video is ultra clean too! If I could get that on the regular, I'd have no complaints.

  • caveportcaveport

    @tedbrah Keep in mind that V-log is very similar to the Alexa log curves. Panasonic have not done anything unusual in the bits used for log capture. It is unusual to shoot 8bit log in the pro industry. I would think that Panasonic are expecting most users of V-log to be shooting 10bit on an external recorder.

    I have done some more testing in bright sunlight with blue skies. The result is great! The overcast days did not look very nice but I think if you expose to the right and take some care in grading the results are spectacular.

    One thing that is very different from standard profiles:The log curve means available light variation on 'run & gun' footage means the LUT will some times require a pre-lut adjustment to put the exposed range in the correct part of the log curve.

    Overall I'm more impressed than I was with earlier tests.

  • tedbrahtedbrah

    @caveport They haven't done anything to the bits being recorded they're just throwing away 3-bits. If they created the profile for the GH4 instead of copying it from Varicam there wouldn't be any banding or macroblocking. The Sony a7 has S-log and the footage coming from that cam looks amazing with great dynamic range, no banding, and no macroblocking. As I said in the previous statement, if you shoot V-log on the GH4 you're only using 5-bits.

  • MisfireMisfire

    I hope Panasonic actually takes the time and optimizes v-log for the GH4 specifically in future updates....otherwise this is just unfortunate.

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