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offbeatbryce
11-07-2017, 08:53 PM
Hello, sometimes with avchd files I experience color correction color banding issues with my 8 bit footage. Someone told me if I transcode to dnxhd it will solve this. Is that really true or would I just be wasting disk space??

balazer
11-09-2017, 11:20 AM
What video editing software are you using? Most modern software can work in a 32-bit floating point RGB pixel format, in which case the editing and color correction process adds only minimal banding when writing to a new 8-bit file. Transcoding to DNxHD makes no difference. Also, what color space are you shooting in? Some color spaces have insufficient color precision in 8 bits.

rayortiz313
11-10-2017, 07:17 PM
I'm not a colorist and really a babe in the woods with this issue but I do want to point put that the white paper for DNxHD encourages color correcting in the codec.

Not trying to contradict you, balazer, just saying that there is cause for people believing, rightly or wrongly, that transcoding helps. I mean I have no clue, this stuff is all over my head.

Here's the text, feel free to clarify my misunderstanding:

"...they can choose to encode 8-bit HD media as 10-bit Avid DNxHD media to maintain pristine image quality over multiple generations of postproduction effects processing. The increased bit depth provides the additional dynamic range necessary for precise color correction adjustments without introducing signal clipping and rounding-error artifacts"

rayortiz313
11-13-2017, 08:19 AM
Came back to to clarify though:

I myself am working in 8 bit (HDV) and decided to NOT transcode,after experimenting with dnxhd.

As our friend mentioned, most software is upsampling the image data to 32 bit to do the processing anyway.

Personally I'm interested in working with as little potential generation loss as possible, I'm not eager to transcode anything.

morgan_moore
11-13-2017, 11:19 AM
8 bit is 256 levels of colour

as you grade you may add contrast to your footage - which requires extra data

there is no 'spare' data in the recorded 8bits of information to make these changes - transcoding cannot create data so a transcode cannot help

transcoding can help you retain the data you originally captured as it moves through subsequent steps in post.

rayortiz313
11-14-2017, 09:08 AM
Ive been dealing with this same exact issue and I think I figured it out---

If you start with 8 bit

Dont transcode- It wont create any new color info anyway.

When you grade: Make sure your software's is working in a high(er) bit depth. The software s basically upsampling the 8 bit to higher bit depth, similar to the transcode.

Grading creates new colors/shades etc

When you OUTPUT you DO need to move to a higher bit depth to keep the new color data you created.

(and to OP- banding happens when there's not enough colors in-between the bands).

Anyone?

some info here:

https://blog.frame.io/2017/08/16/increasing-bit-depth/