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Old September 25th, 2003, 03:29 PM   #1
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Correcting Cinegamma and Matrix in Post (CC)?!

Hi everyone,

Forgive me as I have asked this question before (here and on 2-pop) and never really got an answer...so I'll try again. Bear with me :-)

I was wondering if I shoot with Cinegamma, In post can I add a softer slope to the hard clipping that occurs at 110ire (hard blown out whites)? How do I do this with FCP4 (I'm just learning it). I assume I would make an adjustment to all the clips with the same value?! I really like the "raw" look of cinegamma for the mid-tones and darker areas. Obviously I will slightly underexpose in camera, and I find adding a black diffusion fx helps "soften" this clipping.

Also in regard to color correction, if I use a macbeth chart how do I properly calibrate things in post? I know to shoot the chart for each scene/setup...but what to do with those color values in post? I am finding Cine Matrix darkens certain colors too much, but should I just shoot normal in Matrix if I'm going to color correct?

Sorry for so many questions, but finding information on these subject is hard. I know video from Betacam and DV but I'm trying my hardest to get the most out of the DVX for music videos and I'm happy to spend time color correcting in post to get that "polished" look.

Thanks for any help guys/gals! I know these are more advanced questions, but there's no film school for this kind of stuff...just other people's experience.
Appreciate any info!

Brian Broz
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Old September 25th, 2003, 07:26 PM   #2
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Brian,

Unfortunately, there is not a way to bring back detail that is lost once the values go over 109%. However, the issue that you are inquiring about has more to do with the lack of knee when shooting in Cine-Gamma.

It has been my experience that the three different normal gamma settings (Low, Normal, High) have a built Auto Knee that sets in somewhere around 90IRE and provides the normal and more natural looking slope to maintain as much highlight detail as possible before clipping sets in at 109IRE. However, the Cine-Gamma setting seems to have no knee at all. Without any knee, the Cine-Gamma setting seems to smack into hard white at around 80IRE. Aside from limiting your highlight ceiling, it provides an incredibly ugly and artificial looking digital glow around the highlights that look like the highlight area was exposed to a melting plutonium rod! It's horrific on skin tones.

The bottom line is, Cine-Gamma isn't really suited for images that are intended to be screened on video. Cine-Gamma is intended for projects that require a film out. It's main function and design is to create a denser picture on negative. By forcing the image exposure down, you end up with highlights that maintain detail on film and take on a wider dynamic aesthetic on film. Of course, the beauty of Cine-Gamma, is that it maintains shadow detail better than any other Gamma selection. In other words, you have to seriously under expose for the highlights, but you have the sensitivity to not lose the shadows.

Regardless of the gamma setting on this or any other camera, there is no way to bring back detail once it goes over 109IRE. You can BRING OUT detail in areas between 95IRE and 105IRE by clamping down on the gamma in post. But this, of course, is only if the detail is there to begin with.

In regards to color correction:

I am experienced in color correction using a DSC CamAlign chart in post. By shooting this chart on set and then bringing up that shot on a waveform monitor, you can adjust the values to match "True Color". However, I have not done any color correction with a MacBeth. I imagine there would be a way to sample the color chips and then apply those values to the clip. But I am not a post guy. So my experience is limited.

In my opinion, for music video type applications, you would be better off choosing one of the normal gamma settings instead of Cine-Gamma. This will allow you more "room" and more flexibility at acquistion. Not to mention producing more "normal" looking images on video. Then, in post, experiment more with color styling, instead of color correcting. Music videos are such a stylized form that they lend themselves to experimentation than just replicating a cinema aesthetic.

Jon
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Old September 25th, 2003, 07:38 PM   #3
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<<In my opinion, for music video type applications, you would be better off choosing one of the normal gamma settings instead of Cine-Gamma. This will allow you more "room" and more flexibility at acquistion. Not to mention producing more "normal" looking images on video. Then, in post, experiment more with color styling, instead of color correcting. Music videos are such a stylized form that they lend themselves to experimentation than just replicating a cinema aesthetic.>>

Cinegamma captures a pretty flat response, thus gives you almost another stop of latitude. If you can control highlights from clipping, it will give the maximum image to manipulate in post.
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Old September 25th, 2003, 08:11 PM   #4
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<<Cinegamma captures a pretty flat response, thus gives you almost another stop of latitude. If you can control highlights from clipping, it will give the maximum image to manipulate in post.>>

Forgive me if my statement was unclear...

As stated, choosing one of the normal gamma settings 'will allow you more "room" and more flexibility AT ACQUISITION'. With the normal gamma curves providing an auto knee function, you will have more flexibility to over-expose or ride a brighter exposure while shooting.

If you are looking to do intense image manipulation in post and require a flat and raw image to exploit, then drasticly underexposing your image using Cine-Gamma may be the best solution.

Make sure you set your zebras to 80 and elminate them from your finder.

My statement regarding post was in reference to color correction. Suggesting that attempts to replicate accurate color may not yield the desired results. Whereas embracing the ability to exploit stylized color may be more appropriate for many projects within the form.

Also as stated, I am not heavily involved with post production. So my comments lean more towards my control of the image at the point of acquisition.

Jon
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Old October 1st, 2003, 01:37 AM   #5
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I was used to doing the film-like curve correction in post with my TRV950..and logically, it should seem that the best solution if you wanted to do any correction in post would be to just record it in normal gamma, make sure it was a bit under-exposed, and then edit the curve in post completely.

However, for me, i've found the cine-like curve on the DVX to work extremely well most of the time, so i endup using that and then editing the curve after words a bit. My only problem with color correction most of the time seems to be really flourescent looking reds...i can kill them by dropping down the chroma but then the other colors die down too. This camera captures some incredible greens outdoors, so i just kill down the reds in post if there are any.

I guess, do whichever method looks best to you, but always remember to under-expose the image a bit. Like someone else said, once the CCD clips(overexposes) there's literally no data there for you to use, no matter how much you correct.
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Old October 1st, 2003, 01:27 PM   #6
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Thanks...now what about low light noise?

Thanks for all the replies.
But what about low light noise (in 24p/cinegamma)? I have been really surprised to see how much noise the camera has in very low light with color (ie. red wall, wood desk etc) in cinegamma/24p mode. I suppose in really low light situations, it may be best to use another gamma setting.
Once I add a bit of light the problem goes away. This noise is exhibited very well on "blue mode" on the Sony PVM monitor.
Anyone care to comment on reducing this noise in post? (For those time when I can't light). I hear Magic Bullet works well. Again any comments are appreciated.
Cheers,

Brian Broz
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Old October 2nd, 2003, 09:34 PM   #7
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I noticed a lot of noise on a shot of a person in a red sweater. It was mostly in the lower light shadowy areas. Is this a characteristic of cinegamma, 24p or just low light ability overall?
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Old October 2nd, 2003, 09:53 PM   #8
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I think the cinegamma adds some saturation so it might make reds particularly look more noisy. I find that usually turning down the chroma helps tone down the reds. unfortunately it tones down everything else so if you have a lot of color in the shot, you might just have to live with the noise if you want the cinegamma. otherwise, if you only have wood/red and not much color, try lowering the chroma level.
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Old October 2nd, 2003, 10:19 PM   #9
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Guys, I have a question regarding gamma etc in general. Why would underexposing help at all. Wouldn't you then be crushing your blacks and so lose detail there instead of in the highs? It it simply a matter of our eyes liking more black than blown out whites?

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Old October 2nd, 2003, 10:24 PM   #10
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If you have a very dark room then I guess it's just a tradeoff, but in general I think the reason is that CCD's over-expose(clip) easier than they under-expose.

Also, when looking at an image you might want to see where you can normally see i.e. where there is light, rather than where there isn't. i.e. if the audience can't see something cause it's in a dark shadow, they might not notice it as much as the white blotch on the screen where a highlight should be.

Someone else can probably explain this better...
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Old October 2nd, 2003, 10:26 PM   #11
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Aaron:

DV (as well as HD) seems to hold detail shadows better than highlights in general (as compared to film - broad generalization).

Cinegamma flattens out adjustments most cams make for limitations of video. It's designed for viewing in darkened viewing conditions:

http://www.adamwilt.com/24p/index.html#GammaSettings

has lots more info about this.
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Old October 7th, 2003, 10:54 AM   #12
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I've had the "blown highlights" problem with Cinegamma also, and really the best CC you can do is to take the clips into After Effects, or get Color Finesse for FCP, and using the curves tools, add a nice knee to the image when you have blown highlights. You basically want to adjust the curves filter so that it slopes off at the top. This won't get you any more detail out of the highlights, but it will prevent the "clipped" look to the highlights that can be quite garish. Additionally it gives you finer control over what the knee will be on a scene-by-scene basis, rather than the camera dictating to you how to shoot. So don't be afraid of Cinegamma, just realize that it may take more of your time in post to correct anything that clipped in the highlights. As of now, I can't even imagine not shooting in Cinegamma it's so beautiful compared to the other options out there.
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