7.5 % set up question

[Mat Cain]

I admit I am a little slow and perhaps one of the least "tech" people in this forum but I am confused by the 7.5% set up.

What I do know is that the NTSC standard uses the 7.5% set up. So I have set it it in Edius (my editing app). However, I have several cameras and several of them have different settings. It seems that all of my cameras should reflect the same 7.5% set up. - Isn't that right?

I have noticed that some of my DV cameras bring in pretty light (almost washed out) video as opposed to my Panasonic HPX 300 which brings in much darker black levels. So some cameras look washed out while others appear to lose detail in the shadows - does this have to do with the 7.5% set up or just wacky camera settings. The Panasonic is new and currently at default settings.

Either way - is there anyone with some definitive info on 7.5% settings should be to meet NTSC standards.

If I am missing something obvious and sound like a moron please excuse this post or better yet - kindly point me in the right direction.

Thank You,
Mat Cain

 

[jmarkham]

First off, 7.5% is an analog value for NTSC... and your cameras are
working in a digital space. Depending on the bit-depth of your digital
camera and the gamma, there will be a Y' digital number (usually 16 in an
8 bit camera) that roughly corresponds to the NSTC 7.5% "black."

Do all of your cameras support ABB? If not, then what the camera sensor
thinks is black may not be accurate. If your camera has a 7.5% setting and
doesn't support ABB, then it's "merely a suggestion"

When cameras disagree (and different cameras from different manufacturers often
do ... for a variety of reasons), this is when your color-gradist will adjust the contrast,
gammas and chroma to get an acceptable match and to conform to broadcast
standards.

Anything you can do to match cameras and settings (AWB / ABB)
will make their life all the easier. But, due to variations in sensors,
electronics, gamma's, codec bit depths, etc., it is an imperfect
mapping from camera to camera as to what the analog 7.5% actually
means.

What's your monitoring situation?


jeff