> Is anything really happening to the "essence" of the QT or is it setting
> metadata flags on how to interpret the footage?
There is absolutely something happening to the image itself, not metadata.
Do a simple test.
Download a testchart.
http://www.belle-nuit.com/testchart.html
This is a video test chart. It has both legal and illegal levels (blacks
lower than 16 and whites over 235).
AVID IMPORT TEST:
Import into Avid, tell it the source is 601/709 (name it 601/709).
Also import the Avid, telling it the source is RGB (name it RGB).
Look at the two on the waveform (can be the Y-waveform in CC mode).
The 601/709 import will show a correct color bars pattern, and it will alsow
show you that there are some illegal boxes (blacks below 16, whites over
235).
The RGB import will show the 0-black raised to 16, and the 255-whitelowered
to 235, and all the numbers in between will be off.
This shows that if a file was created to be broadcast legal, you should
maintain its levels upon import.
AVID EXPORT TEST:
Take the properly imported test chart (the 601/709 one).
Export to JPEG, one time at 601/709, one time at RGB.
Open the results in Photoshop.
You will see that the 601/709 export has maintained all levels. The 16-box
still measures 16, the 12-box still measures 12, the 235 still measures 235
and 255 still measures 255.
You will see that the RGB export has crushed all blacks from 0-16 and
lowered them all to 0, and has clipped all whites from 235-255 and raised
them all to 255.
QT EXPORT TEST
Open the graphic in QT Pro, export to Avid Codec two times, one with the
601/709 setting (clip A), one with the RGB setting (Clip B).
Import Clip A into Avid, telling the Avid that it is 601/709.
Import Clip B into Avid, telling the Avid that it is 601/709.
Look at these clips on the Y-waveform.
A. will show the same levels as the original (0 is till 0, 12 is still 12,
16 is still 16, 235 is still 235, 255 is still 255).
B. Will show you that everything is now between 16 and 235, but all the
levels are off. 0 is now 16, 16 is more than 16, 255 is now 235, 235 is
lower than 235.
--
Job ter Burg
film editor - NL
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