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DPX Gluetools demo question / DPX shadow crushing [message #1033]

Wed, 23 June 2010 18:58

peterb

Messages: 2
Registered: June 2010

Junior Member

Hi ,

I'm about to purchase Gluetools to enable us to export DPX
from FCP for Baselight and other DPX grading suites.

My workflow is to render RED QT files in LOG gamma and then
online in Prores 444, maybe AJA RGB uncompressed and
export DPX.

Using the Gluetools demo, when I access the DPX colour codec
setting and select anything other than LOG, click OK
then re-enter the window it defaults to LOG ignoring
my selection. Also rendering in any of these DPX codecs
results in the same DPX look ?

Lastly importing these DPX into Color shows that the
blacks are crushed. I have a linear ramp test frame
and the bottom 20% is reduced by about 10% crushing
the shadow detail. Is this normal ?

I don't have much DPX experience so this could all be
finger trouble.

Another query, if I log and transfer RED files in native,
ie QT wrapped RD3, and then export DPX will the Gluetools
DPX log encode make use of the 12 bit RED source files ?

thanks
Peter

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Re: DPX Gluetools demo question / DPX shadow crushing [message #1034 is a reply to message #1033 ]

Wed, 23 June 2010 20:55

robertmonaghan

Messages: 472
Registered: September 2006
Location: Santa Barbara, California

Senior Member

Hi,

Many of your questions requires some knowledge of what you are doing with DPX.
There are many sources on the net.
You need to understand QuickTime and its limitations.

1 - Do not use QuickTime Player or FCP to export frames. These will clamp everything to 8-bit. Use Compressor for a better conversion.

2 - Under certain circumstances, the Mac will do a Gamma Shift to RGB imagery. You need to understand where this happens. (Our software doesn't touch the gamma, but unfortunately, we are affected by it.)

3 - In System Preferences, be sure to set the CineonDPX settings for your LogC/Lin conversion values.

4 - LogC (Kodak Cineon Log) is not Red Log. We don't support Red Log, as it changes all of the time. Ie: there isn't a published (or set) Gamma curve we can use from Red. You will need to figure out how get the imagery out of "Red Log" space.

Good Luck!

bob.

[Updated on: Wed, 23 June 2010 20:56]

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Re: DPX Gluetools demo question / DPX shadow crushing [message #1035 is a reply to message #1034 ]

Wed, 23 June 2010 22:43

peterb

Messages: 2
Registered: June 2010

Junior Member

Thanks Rob, the Sys Preferences sorted my problem out.

FCP , 8 bit, really , that's a worry.

Thanks again, we'll get a couple of Gluetools, great product.

Razz

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Re: DPX Gluetools demo question / DPX shadow crushing [message #1036 is a reply to message #1035 ]

Wed, 23 June 2010 22:45

robertmonaghan

Messages: 472
Registered: September 2006
Location: Santa Barbara, California

Senior Member

FCP is fine, as long as you don't export using the "Export->Using QuickTIme Conversion".

This is a very well documented problem. Internally, FCP uses a 32-bit float colorspace. However, when exporting through QuickTime, the imagery gets clipped. Thats why it is recommended that you use "Send to Compressor" instead. The 32-bit float data is exported to a 10-bit DPX properly.

bob.

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