Color Correction:Broadcast Safe - Render Bug?

Gual G5 - 2 Gigs Ram - OS X 10.3 - FCP 4.02 - QT 6.4 - Render plugin - DV source media - Sequence settings: Video processing: 8 bit YUV: Process as white.

Turn on "Show excess Luma" in canvas

Place a clip with out of range luma in sequence

Place playback head on the frame that displays the yellow warning sign maximum amount of red zebra pattern

Apply the Color Correction:Broadcast safe filter to the clip.

In the Viewer Filters tab, set the "Mode" of the filter so that the Red zebra pattern turns to green and the green check sign with the arrow indicating maximun legal luma levels replaces the yellow warning. I find that "Consevative" or "Very Conservative" usually works.

Render the clip.

After rendering the same frame that was legal, is now out of range as indicated by the return of the yellow warning sigh to the canvas. I can see the change in the scopes as well.

Please give this a try. I thought I was going nuts. Clips that I had corrected, were suddenly out of range again the next day. Then I realized that it only happened to clips I rendered.

It is not a good thing to spend hours color correcting only to have rendering screw it all up. If the CODEC is rendering this much luma shift, we have a problem.

Rob

It looks like that this is only happening on clips with significant excess luma with the Broadcast Safe filter used on top of the 3-Way Color corrector. However, I use this combination a lot on source DV from less expensive 1 chip cameras that tend to over expose and blow out the highlights.

In any caase, the luma of the clip should not shift after rendering.

Rob

All system parameters as above.

Create a title movie in Live Type using white as the text color. Mine happens to be a lower third that incudes a photoshop graphic which also contains white.

Import the movie into FCP. (process white as White)

Turn on show excess luma in canvas.

Place a clip with legal but maximum white in the sequence.

Place the title movie over the clip.

Place the playback head over a frame where the green check with the arrow indicating maximum luma comes on.

Render the clip.

The frame that was legal prior to rendering is now out of range. The change in luma is clearly visible in the scopes as well.

100% repeatable on my system.

If we are not getting accurate luma readings from real time or preview effects or filters, then how can we possibly be accurate with color correction?

Rob

What video processing are you using in FCP?

All the best,

Tom

Sorry, I should have restated this from my first post.

Gual G5 - 2 Gigs Ram - OS X 10.3 - FCP 4.02 - QT 6.4 - Render plugin - DV source media - Sequence settings: Video processing: 8 bit YUV: Process as white.

From my previous post
"It looks like that this is only happening on clips with significant excess luma with the Broadcast Safe filter used on top of the 3-Way Color corrector"

I've determined that this is NOT the case. The parameters of my original post are correct. I am seeing this problem consistently. Un-rendered clips that show in the canvas as in range, become out of range after rendering.

What is the point of real time color correction if the real time color corrected clips do not accurately represent the clip after rendering.

Rob

Rob:

As 10.3 is a spectacularly dangerous release of the operating system, it might make sense to upgrade to 10.3.1 and see if that fixes your problem.

(Though I doubt it, at least your system will be safer.)

Also, with the 4.1 upgrade out, one of the bugs they say they fixed was the Broadcast Safe filter.

Might be worth the upgrade time.

Larry

Did all that. No difference. The bug in the broadcast safe filter was different than what I have found. I really don't think it is in the filter itself, rather in the way the codec renders RT FX to the screen buffer differently than it renders straight DV. And/or in the way that preview data is interpreted by the code that checks for luma levels. My guts tell me that this is a codec issue. Either way is sucks because it makes accurate color correction impossible, well at least very cumbersum. I see a similar problem show up with keyframes and color correction. I could go on but I have to get the Turkey ready for tomorrow. The bottom line is that you cannot trust what you see playing or what the Check Luma Levels tells you in RT.

Rob