A little grading advice (Banding in build 15 footage)

[Greg Huson]

I'm grading some build 15 footage in Avid DNX175x via Rubber Monkey Extract. Did a lot of 'pregrading' in RedAlert, which solved most of my problems, (the filmmakers had very beautiful but aggressive grades in the field, which needed to be 'neutralized' a little to recovers some blacks, which I'm now re-crushing with less trouble.)

In a very few shots that seem well exposed, however I'm getting stepping/banding in the areas of subtle gradation- In most cases I was able to suppress this in RA/RL by changing detail and using Gauss algorithm, but a couple shots are still problematic.

What's the trick to hiding this noise/blocking/banding? I've seen that a few other folk have dealt with this, too, so any tips will help.

Will full debayer make a difference? I can't re-render the whole film, but I could certainly rerender the trouble shots.

If you've seen this, and dealt with it, I'd appreciate the benefit of your experience.

 

[Michael Lindsay]

http://www.reduser.net/forum/showthread.php?t=18930&highlight=banding

Despite you exporting in 175x it will not be a 10bit file after a non'fast-import'. How is it importing?

The easyist way to make sure you have a 10bit file in Avid would be a 16bit tiff export then import into a 10bit codec from within Avid.

If you do this your banding will disappear till you truncate to 8bit.

Please report back your findings

regards

Michael

 

[Lucas Wilson]

Greg,

Are you sure this is a problem with the footage, and not an 8-bit DVI monitor? You mention using RA, which does not output to SDI, so I'm assuming you're looking at this on an 8-bit screen.

Lucas

 

[Greg Huson]

Greg,

Are you sure this is a problem with the footage, and not an 8-bit DVI monitor? You mention using RA, which does not output to SDI, so I'm assuming you're looking at this on an 8-bit screen.

Lucas

I'm only using the histogram for ballparkin' the exposure, then final grading the DNX. The banding is clear in my BVM on the SDI output of the Avid DX box.

I saw it a LOT on the original DNX 36 offline, which was just the QT reference files imported as DNX, but now I'm only seeing it on a couple shots in the 'Full Rez' HD. I tried uncompressed 422- same problem on same shots. I'll try full debayer, but I just wonder if this is just a matter of knowing how to hide the problem.

gh

 

[Michael Lindsay]

Your looking at 8bit clean 35mm DOF footage. It will band.

Try 16bit tiff into Avid 10bit..

M

 

[Greg Huson]

Your looking at 8bit clean 35mm DOF footage. It will band.

Try 16bit tiff into Avid 10bit..

M

I'll try that on the trouble shots.

 

[Greg Huson]

Your looking at 8bit clean 35mm DOF footage. It will band.

Try 16bit tiff into Avid 10bit..

M

Definite improvement from using 16bit TIFF as the intermediary format. Makes no sense, of course- why should moving DNX175x from QT to MXF (importing into Avid) make it 8 bit? Yet, I can clearly see a difference as you've suggested. Additionally, I noticed... and here's a little embarassing bit... the Symphony DX has an 8-bit 'full resolution' setting in the timeline, and a 10bit 'full resolution' setting in the timeline. Oops. Smoother in 10 bit display, of course, but still an additional difference when tiff is the intermediary. Thanks for the tip.

 

[Michael Lindsay]

no problem...

Hopefully Avid will fix the 10bit issue soon..

good luck

Michael