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Old November 21st, 2002, 11:56 PM   #1
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Color Adjustments

I was watching one of the documentaries on the new Lord of the Rings DVD, about digital color adjustments. They were showing the unadjusted film against the digitally adjusted film, and I immediately thought of some of these DV discussions.

The unaltered 35mm film looked no better, at least color-wise, than anything out of a good 3-CCD DV camera. After they adjusted the levels, it looked superior. But the point is if that can be done for film, it can be done for DV.

So, with the right color adjustment it sure seems to me like 30-fps progressive DV can be made to look like film, and it has less to do with film itself and more to do with the color processing.
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Old November 22nd, 2002, 01:41 AM   #2
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I read somewhere on here that more film DPs are learning to get those color adjustments in camera though. Sorry, don't remember the thread.
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Old November 22nd, 2002, 02:28 AM   #3
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Peter:

That's an interesting theory. One has to keep in mind that if the same scene that you were watching on the DVD had been shot with a 3 chip DV camera, it would be a far inferior image. The contrast range is more limited with the digital camera, so you would see less detail in the shadows and highlights. No amount of color correction would render an image similar to a 35mm capture of the same scene.

That said, skilled color correction can make a big difference regardless of the original medium.

There have been many exhaustive (and sometimes exhausted) discussions in this section of DVinfo.net about the various factors that can help digital images appear more filmic.

Josh, the general trend for digital filmmaking particular in the HD world is to capture a decent image and do the tweaking in post rather than in camera. The Viper system is all about this, recording raw data from the camera with no processing. There are a few folks such as Robert Rodriguez who are dedicated to finding their own settings in camera, however.
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Old November 22nd, 2002, 08:03 AM   #4
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Sure, the DV camera can't match the resolution or contrast of 35 mm. Someday when HD DV finally is available maybe we'll get there. Consumers are never going to have (or want) 35 mm movie cameras, but I think eventually DV will rival it at least when viewed on a TV set.
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Old November 22nd, 2002, 09:30 AM   #5
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* * COLOR CORRECTION * *

Color correction is a necessity regardless of the medium, in my opinion.

Making the images more appealing through, just highlight and shadow adjustments can change the image with excellent results.

I have been experimenting with my short film color correcting and it is very rewarding.

As far as adjusting the camera, I guess everybody has a comfort, some use the camera, others in post.

Cheers!
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Old November 22nd, 2002, 10:21 AM   #6
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On the TV set fed from a DV source, or any other 8 bit source (this includes HD), you will always be limited in contrast and colour fidelity. This produces results like the colour banding you see in (say) BBC News 24's nice rust coloured backgrounds.

Roll on the day when 10 bit colour is cheaply recordable and widely broadcast - you will be able to colour correct much more finely, and have something visually must closer to film then!

Julian
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Old November 22nd, 2002, 11:12 PM   #7
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10-bit color? You're gonna have to explain something to me then - 8 (24) bit color actually gives you 16.7 million colors. All scientists say that no human can perceive more than a few million distinct shades. So how could 10-bit color make a perceivable difference?
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Old November 23rd, 2002, 12:17 AM   #8
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The big thing with film is that although it has many advantages, even in the best situations you never know what your going to get until it's developed. Even with 4x5 Polaroid's I remember anxiously awaiting the developing to see if the pic were as good as I hoped. To think what I could have done if I could have put those 4x5 transparencies in a Mac and tweaked them some.

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Old November 23rd, 2002, 05:55 AM   #9
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10 bit colour

Peter,

10 bit makes all the difference. That's why high end equipment and tape formats are 10 bit or more - Digibeta, and uncompressed PC and MAC cards are 10 bit.

I'm not familiar with the scientific evidence that humans can't discern the difference between 8 bit and 10 bit colour. I just know they can - just look at a slowly varying gradient when displayed on a digital TV (for example, the rust coloured backgrounds on BBC News 24 transmissions) - it has visible bands in it.

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Old November 23rd, 2002, 09:06 AM   #10
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If I'm not mistaken, the colour banding that I see on the BBC news on my satellite dish is more due to artifacts caused by MPEG2 encoding than anything else. If I saw that on my DV camera I'd be concerned.
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Old November 23rd, 2002, 09:36 AM   #11
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I don't think the evidence says they can't tell the difference between 8 and 10 bit - I don't doubt you there. When 24-bit video cards came out, everyone said humans can only see a few million shades, so 16. 7 million was more than enough.

Now, in audio for example, while no human can probably hear a difference beyond 16-bit sound, 24-bit is very popular in professional contexts because then the sounds can be mixed with greater resolution. So it's not the result that matters, but the intermediate steps to achieve that result that need to have more resolution.

Maybe 30-bit color means better mixing between the colors when the image is being created, and thus the resulting 24-bit image will look better.
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Old November 24th, 2002, 12:18 PM   #12
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of course the big advantage that greater color depth gives is better signal to noise


8bit is 48db, 10 bit is 60db etc

even in a perfectly exposed dv signal there will be areas of the image -- eg shadows or expanses of rich blue sky which will only be around 20 db and thats where the noise shows up.

for my part I would like to see 16bit video depth so I dont have noise up my animation stuff when I mix it with video


its the noise which always gives away the fact it was shot on video no matter what you do to the motion or color adjust.


As for color matching in post - dv compression and noise artifacts tend to show up more - which is why top cams have all the image tweak tools in camera prior to compression
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Old November 24th, 2002, 01:01 PM   #13
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These two sites should help with understanding the 10 bit advantage http://www.digitalvoodoo.net/products/10bit/ The second is Cinesite, www.cinesite.com which does all of it's work at 10 bit. Poke around there a little and read about what they did on the various films and it will give you a feel for the difference.

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Old November 24th, 2002, 11:08 PM   #14
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Then that's basically right, the way I understand it. The extra color resolution doesn't really allow you to see more distinct colors, but in the process of transferring from digital rgb to video, would allow greater accuracy, less rounding errors, and less dithering noise, similarly to the way 24-bit audio mixing accomplishes the same thing.
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Old November 25th, 2002, 04:28 AM   #15
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10 bit (or more...)

Yes, working to a greater bit depth means that postproduction effects introduce less noise visible in the final output, so 10 bit source recording is an improvement on 8 bit.

At both output and input ends - 8 bit has limited dynamic range. 10 bit has a greater dynamic range, permitting shadows to be fuller, and brights to be brighter, all without the banding that After Effects' levels filter would introduce.

I am not claiming that the eye can see "more colours" (the human brain is notoriously bad at colour differentiation, hence the success of things like DV compression). I am saying that the eye can clearly see a wider luma range than that represented by 8 bit colours. Again, 10 bit is better than 8 bit in this regard.

This is why (PAL) video lives in YUV space, and not RGB. YUV treats luma (Y) separately from chroma (here U and V), permitting you to manipulate colour and brightness separately.

Now I come to think about it, I guess 12 bit Y and 8 bit U and V might be a good compromise for broadcast:)

Julian
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