multiple color corrections/brightness & contrast adjusment - how it affect video quality?

kerrying wrote on 4/11/2004, 9:03 PM

Hi all,

Kinda wondering about this recently and thought maybe you guys can come on in and share your thoughts.

Working on a DV project (for DVD output), you color-corrected some events, make adjustment to the contrast and brightness of events here and there, and then at the video bus track, you pass the entire video output through one more color-correction (for whatever reason there is, aesthetic or otherwise). Now, will doing this kind of 2-pass color correction thingy affect the video quality in any way? If so, to what degree? How?

It is rather similar to putting an event through 2 color-corrections (for whatever reason there is).

From what we know and from looking at the diagram from the online help that explains how signals are processed internally, hmm.. the video quality is likely to take a hit.. What do you think?

Cheers,
Kerrying

Comments

TheHappyFriar wrote on 4/12/2004, 6:15 AM

Yeah, if you apply ANYTHING to the video the quality is hit. The amount of hit is based on how muc you do to it (ie raise brightnes by .1 video it modified very little). But, if the video loks beas in the first place and you improve the look, then the quality hit is worth it. :)

kerrying wrote on 4/12/2004, 7:08 AM

Hmm.. yeah, video quality is, right from the beginning, something that is subjective to personal preferrence and perception. Anything we pile on (transition, text overlay, track compositing and etc mean modification to the pixel of the footage), but, how about 2-pass color-correction?

Giving my brain some exercise here (it sure can use some, ha..;) ), I am thinking how accurate and effective can the 2nd pass color-correction be when it is working off "2nd hand" pixel information (after the 1st color-correction is done at event level)..

As color-correction and brightness & contrast adjustment are core adjustment in all my edit work, maybe, alternatively, I should refine my workflow in order to keep all filtering or adjustment to the minimal (should move some of the adjustment to video bus track since they apply to the whole sequence.. hmm..). I guess beside audio noise reduction, very little other filtering (video or audio) will yield better result if you do a 2-pass (mpeg rendering not included, by the way..)

Addition of a video bus track in ver 4 is pretty nifty here, providing multi-tier adjustment capability make applying adjustment precise and flexible, love it..

Thanks for your thought, man, appreciate it..

Cheers,
Kerrying

PS: DVD Buena Vista Social Club, the musical documentary has a pretty browny, hard-edged, high contrast, low-saturation look that is rather nice, it is one of those few looks that remind me that playing with color-correction can be fun.

PS2: having read sooo many of you folks' threads on mpeg rendering and video quality all this while, I got myself thinking and experimenting and now, whenever I do a final render to mpeg2 for DVD, if space is not an issue, I use a 7 Mbps for average bit rate setting instead of the default 6 Mbps of the DVD PAL template from VV 4, because I find that extra 1 Mbps give a very subtle difference in terms of details and sharpness. Max bitrate should stay at 8 Mbps for audio streams and maximum compatibility with players.