Hv30 gradient banding

[jejeson2]

hello,

i did a search in the forum before beginning this thread, and i didn't find any solutions to this.
i have shot some hdv footage with my hv30, and on the camera screen, it looks fine. however after capturing it using final cut, i see a lot of pixelating and grain especially in the skin gradients (when i put my onscreen monitor to 50- 100%). also, when i do aggressive color correction, the pixelating worsens and i begin to see color banding in the gradients.

i have been using native hdv, but i heard that using a good codec when capturing footage should give more color space. i tried using prores and sheervideo, but prores gives a much bigger file and i don't see any significant change. sheervideo claim that you can change 8 bit 4:2:0 footage to 10 bit 4:2:2 and 4:4:4 and benefit from the better color space. does this only apply when you are using a special capture card or via hdmi, or will it work with footage captured via firewire as well?

is there something am missing? am i doing something wrong? i have seen footage on vimeo from the hv30 and the image looks very clear with no banding even in low light situation. why am i getting a bad image? please help........................!

[SenorKaffee]

Please show some examples, original and graded output.

You cannot change the colorspace of the input. HDMI helps a little, because you bypass MPEG2 compression and (IIRC) get 4:2:2 instead of 4:2:0. What you should definately do is work in a project that supports more than 8 bit per channel - it helps to avoid banding.

[jejeson2]

Please show some examples, original and graded output.

You cannot change the colorspace of the input. HDMI helps a little, because you bypass MPEG2 compression and (IIRC) get 4:2:2 instead of 4:2:0. What you should definately do is work in a project that supports more than 8 bit per channel - it helps to avoid banding.

Thanks for the reply SenorKaffee,

how do I create a project in final cut that will support more than 8 bits per channel. All the settings i see in the final cut timeline settings dont seem to show anything greater than 8 bits. also, do you mean that these codecs (sheervideo and prores) will not change anything? should i stick to native hdv?

[Dana Love]

To echo the initial response, visual examples would be helpful.

It sounds like a gain problem that you don't see on your viewfinder. Given the viewfinder is such poor quality, this is a common problem. Are you locking exposure to be sure the gain is set to zero? While gain is a useful feature when used correctly, the HV gives you very little control over how it is used. Locking exposure is the only way to manage gain, albeit in a roundabout way.

Transcoding from HDV to anything else is a good thing, because while you don't gain color information you do simulate the increased color space while also breaking the long GOP format of HDV, which makes the process of correction and rendering better, faster and stronger. ProResHQ is lossless 422.

So, no, don't stick to native HDV.

[jejeson2]

Thanks for the response Dana, am new to HD editing, so i really need guidance here..:hv20-smilie03:


To echo the initial response, visual examples would be helpful.


here, i have included some of the shots that have problems;
notice there is too much grain on her arm, and the dark areas of her face.

i see this even when my onscreen monitor (final cut pro) is set at 25%! when i enlarge the picture (50-100%) it looks horrible. when i do color grading, (which is a must for me), it gets worse. i know that there was little light when this was being recorded, but i have seen videos on vimeo that were made in much less light, and they look far much better. how do you go about something like this in post? i still have a feeling am not doing something right because the light wasn't too low to give such quality.

I will lock the exposure next time i do my filming then. Just to get what you said clearly;

you do simulate the increased color space while also breaking the long GOP format of HDV, which makes the process of correction and rendering better, faster and stronger.

Does this mean that prores actually simulates the 4:2:2 10bit color space out of 8 bit 4:2:0? If so, does this help in such a situation?

thanks in advance....

[jejeson2]

Hey,
also, prores seems to take more rendering time than native hdv... any other codec that would take less render time and hd space?

[Dana Love]

Your experience with HDV is unusual. The Apple white paper (http://images.apple.com/finalcutstudio/resources/white_papers/L342568A_ProRes_WP.pdf) gives some detail about ProRes (though the hyperbolic subject titles are a little much), and there's an excellent article about it over on Creative Cow (http://library.creativecow.net/articles/wilson_tim/ProRes01.php).

The render and compression time for HDV should be longer than for ProRes inside Apple's tools.

A couple of quick thoughts about your images: the middle image is a JPG and the other two are PNG. In order to really evaluate the images, the same size and format should be used.

It looks like the image was captured with a lot of gain. My experience with the HV is that an obscene amount of light is needed to set gain to zero...which sounds like your goal. While "gain is good" arguments (which I now must do as a homage to Gordon Gecko) are right, they make grading complicated. It sounds like you want crispness, and are distressed by the fuzzy nature of your images after grading.

What are you using to color grade? If it's Color, I'm poking around a problem where my graded images always look fuzzy in FCP...but fine after compression. I don't know why it does it...yet.

[SenorKaffee]

I'm on a PC so I can't tell you much about FCP, but Dana is right. It looks like there is some gain and the picture is also pretty soft. A bad combination, because sharpening will make the noise even more visible.

If you want to see how good the HVx handles the current lighting situation, switch to Spotlight mode and then switch back to the mode you want to record in. Spotlight mode does not apply gain, so you can see what the cam has to compensate for.

[jejeson2]

Y It sounds like you want crispness, and are distressed by the fuzzy nature of your images after grading.

What are you using to color grade? If it's Color, I'm poking around a problem where my graded images always look fuzzy in FCP...but fine after compression. I don't know why it does it...yet.

yeah,

i want clear crispness, but my output is nothing close to that. i used the mac usual mac way of taking screenshots (command+shift+4) then uploaded them as png's, not to sure why the file type changes though.

for color grading i use final cut with some GenArts Sapphire plugins. well i do have shots in other with good lighting, but as long as there is a shadow on my subjects, i most likely will get grain. i see the grain even before color grading. i read somewhere that filming in cinemode will help bring the camera gain close to zero gain, not too sure how true that is though.

i have never used apple color, but do u think color could handle C.G better than final cut? also, does hdmi help when capturing from tape? one more please..... is it true that prores will make a 10 bit 4:2:2 color space out of the native 8 bit 4:2:0?

[Dana Love]

Spotlight mode does not apply gain, so you can see what the cam has to compensate for.

I didn't know that! That's a really helpful technique.

I use the Lytecap to lock exposure, and I swear by it. I have two in my bag now, and they're used two or three times a day. Locking exposure at anything tighter than 1.8 at full wide (so, 2.0) means the camera isn't applying gain. I used to think I was correctly exposing an image...it turns out I was nearly 1000w of hot lights shy of good exposure.

The epiphany wasn't a positive one as regards the HV low light performance, but I really wasn't trying for low light. It did tell me I needed a lot more light, and I expect a similar exercise will tell you the same.

We're really challenged with the HV to figure out proper exposure. When I tried to lock subject exposure between 70% and 100% IRE (by toggling between the two zebra settings and adjusting exposure manually), Color's scopes (after capture and without any pre-processing in Compressor) put my subject at about 55% exposed. That's like 50% off, since I was aiming for 80% or so!

[Dana Love]

i have never used apple color, but do u think color could handle C.G better than final cut? also, does hdmi help when capturing from tape? one more please..... is it true that prores will make a 10 bit 4:2:2 color space out of the native 8 bit 4:2:0?

I know it's not completely correct, but I figure if Color works for the Coen brothers, it'll work for me. :) The interface takes a little getting used to, but f you're near an Apple store they should have a Creative who can give you lessons, or there are books and classes available. I use the Creative for One to One lessons, the books, and the colorist we keep on staff at work. I try not to annoy her, though.

HDMI does help, though Duke is probably a better source of information on HDMI capture. I'm not saying he's the only one, just that I've read his HDMI capture posts. The benefit of HDMI is that the signal hasn't gone through the HDV encoding process, as I understand it. I'm not sure what color space it gives you.

And yes, ProRes transcoding does make something out of nothing. There's some extrapolation that takes place, but the real power is that all your changes are made in the new color space. This leaves you putting changes into a data stream you wouldn't otherwise have access to, which should give you a more nuanced image.

Then you compress the hell out of it, if you're going to the net. :)

[Ian-T]

HDMI captured "live" (not off tape) gives you 4:2:2 colorspace instead of the 4:2:0 HDV. Capturing off tape over HDMI only gives you a blown up 1920x1080 image which still went through MPEG-2 processing. It will not help your current situation though. Spotlight mode does not add gain...but you also lose the manual whitebalance.

[jejeson2]

Then you compress the hell out of it, if you're going to the net. :)

i hate that part.... am definitely going to the net..... :(

anyway, thanks guys... i actually tried out the spotlight mode and i just realized i have been filming with a considerable amount of gain (since the image looked darker indoors). i guess am left with no choice but getting a few lights to work with....

thanks again, your response helped out a lot.. :)

[Dana Love]

Ian > me. Capture via HDMI isn't simple, is it? You need an HDMI card in your computer, and that slaves you to a desktop...or are there laptop cards available?

[SenorKaffee]

There are no laptop cards available, there is only a DIY project connecting a regular BlackMagic Intensity via bridge to an ExpressCard slot.
http://hv20.com/showthread.php?t=18542