Latest post Tue, Jan 4 2011 7:12 PM by Igor Ridanovic. 11 replies.
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  • Sat, Dec 11 2010 10:35 PM

    • Ivo
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    DPX to DNxHD wrong color

    I got DPX files from Nucoda. I converted them to DNxHD 1:1x files. The pictures are missing deep black colors. Is my color space wrong? How to add the right color space?

     

    1080/25P PAL Rec 709

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  • Sun, Dec 12 2010 7:16 AM In reply to

    Re: DPX to DNxHD wrong color

    Were the DPX's in Rec709? If so, how did you convert to DNxHD, using what app and settings?

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  • Sun, Dec 12 2010 6:38 PM In reply to

    • Ivo
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    Re: DPX to DNxHD wrong color

    I think it is 709. I just set it up to 1080/25P and 1:1. I couldn't find a setting for the color space.

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  • Mon, Dec 13 2010 4:56 PM In reply to

    Re: DPX to DNxHD wrong color

    Use an ITU 709 LUT. MetaFuze only exports in the YCC color space. 

    Etienne Allard
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  • Mon, Dec 13 2010 6:52 PM In reply to

    • Ivo
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    Re: DPX to DNxHD wrong color

    How do I do this?

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  • Mon, Dec 13 2010 7:04 PM In reply to

    Re: DPX to DNxHD wrong color

    Select your transcode, in the Detail view, there's a property named LUT, click on it and a list of available LUT should appear. It is also possible to create some LUTs by right clicking on a group/transcode and selecting Edit LUTs.

    This is all fairly well documented in the MetaFuze user guide which can be found in <your MetaFuze installation path (ex: C:\Program Files (x86)\Avid\MetaFuze)>\Doc\Avid_MetaFuze_User_Guide.pdf. Look for Using LUTs in MetaFuze.

    Etienne Allard
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    Avid

  • Mon, Dec 27 2010 10:43 PM In reply to

    • Ivo
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    Re: DPX to DNxHD wrong color

    Do I have to choose the same LUT in the folder line and the transcode line?

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  • Tue, Dec 28 2010 5:20 PM In reply to

    Re: DPX to DNxHD wrong color

    I believe you need to use the LUT only on the transcode line. You can test it real quick with a single DPX file and see if and how it works.

    Igor Ridanovic

    www.HDhead.com

  • Mon, Jan 3 2011 10:55 PM In reply to

    • mtahir
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    Re: DPX to DNxHD wrong color

    I have 10-bit LOG DPX files which came from Cintel diTTo scanner. This is S16mm. I used 'Printing density' as the option for a LUT as I didn't know what I was supposed to use. Is ok to get an idea of what the image looks like or do I need to find some specific LUT for it?

    After doing some hunting around for info, some say that you shouldn't use a LUT that say a lab provides because it's geared very much towards their process. I also read that I think AE has a set of LUTs to intrepret footage for different film stocks so that you can an idea. I don't know really as it's kind of new to me.

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  • Mon, Jan 3 2011 11:13 PM In reply to

    Re: DPX to DNxHD wrong color

    The lab may be able to give you a LUT.

     

    If not, "printing density" is a good starting point. It's a log to lin LUT using standard values. The picture will look better in the MF viewer when you apply this LUT on your scanned material, but it may still be quite a bit off.

    You can click on the "edit LUTs" button at the bottom and tweak the values until you get something that looks reasonably good. Save that LUT and use it for the rest of yor scans. Remember, this is just a neg scan, not a final color timed element. The color is usually less than perfect at this stage.

    Igor Ridanovic

    www.HDhead.com

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  • Tue, Jan 4 2011 1:58 AM In reply to

    • mtahir
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    Re: DPX to DNxHD wrong color

    Thanks, Igor.

    I'm just trying to get my head round all this stuff. I've was trying to see what the negative looks like but I've realised the there is a difference between the filmstock of the negative and then the film stock used for the printing. In essence, I'm not really going to know what the original (uncorrected) film looks like unless it's printed?

    I found this graph on the ARRI COMPANION TO DI book which seems to match the numbers on the "Printing Density" template in Metafuze. I've seen these numbers elsewhere as well.

    I'm curious about this DPX file in that on it's own you get that washed out image. But then converting in Metafuze, I can select ITU 601/709 format and bring that into MC5. Which is the better way to go?

    Is the bottom line on DPX files that no matter what, you have to do some colour correction on them in order to get the image you want or is the case that if you get a LUT from say the lab or from the film manufacturers, what you now see is kind of what you shot (without any kind of fixing to get the look you want)?

    Thanks

     

     

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  • Tue, Jan 4 2011 7:12 PM In reply to

    Re: DPX to DNxHD wrong color

    We're straying away from the thread subject, but...

    DPX is a descendant from Cineon, a file format Kodak developed specifically for film negative scanning. DPX aims to preserve the full dynamic range of film negative in a 10 bit file. Film negative has a linear response to the light in the (log) scene and this is reflected in the DPX file non-linear gamma. Because the value distribution in the file is logarithmic, it is possible to "squeeze" more information in 10 bits than what would be possible with a linear light distribution.

    Original camera negative stocks and print stocks are formulated to complement one another. A printing density LUT approximates the look of the print stock. It is not quite exact because each print stock has its own characteristic curves that affect color.

    The best LUT to use would be the printing density LUT. If you get a better looking color with the ITU 601/709 LUT this could indicate the files were scanned differently or processed after scanning. Whatever LUT you select at this stage will have no bearing on the final color. The idea behind the LUT in MetaFuze is to give the editor color that's somewhat close to what the finished film may look like. Color management in MetaFuze is isolated from the rest of the post process. Unless you are going to use MXF files generated in MetaFuze for the final product, just dial the color that looks reasonably good so the editor can work with it.

    Yes, DPX and most other file based formats need color correction. You could theoretically get the exact look during the production and maintain that look through the post without color correction, but that rarely happens. Also, the line between color management (LUTs) and color correction in many digital formats is getting blurry these days.

     

    Igor Ridanovic

    www.HDhead.com

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