Shot footage with 7.5 IRE

A

aronprigg

Member
I thought I had this ire thing figured out and have always shot with 7.5 and most everything goes into an avid is edited by someone else and looks fine. I was under the impression that it would be more accurate with an analog field monitor.
So now I am editing in final cut and here is my workflow. Shooting 24pA squeeze mode-digitize as normal dv-take file from capture scratch and drop into cinema tools and run reverse telecine creating new file- import and designate anamorphic then edit with that new file. I calibrate my edit monitor to camera bars and everything looks and works great. I then export 24p out to dvd studio pro and create 24p anamorphic dvd and it all works except the black level is washed out on the footage.
Going back to my timeline and import apple color bars, they are indeed different and darker. I guess I have been editing in my own little world were everything is boosted 7.5 ire. Is there any way to make final cut adjust for this without adjusting the black level of my clips? I have looked and looked but cannot seem to find any controls that relate to the difference between 0 ire and 7.5 ire.
Aron
 
You should "never" record with the 7.5IRE black on a DV camera as it does it wrong. Digital video is based upon an 8bit scale, with code values ranging from 0 to 255. Codes 0 and 255 are reserved, so are not used by video. Black is always at code 16 (giving room for super black when dubbing from old, analogue sources) and white is at code 235 (leaving room up to 254 for super white). This scale is referred to as REC601 - an international standard.

When you set the camer to 7.5IRE it no longer records black at 16, but now records it around code 32, which as you can see, is wrong. All digital video the world over should have digital black at code 16, whether it be DV, DVCpro50, HDCAM, DVD etc.

FCP represents this 16-235 legal video range as 0% to 100% on it's scopes. These are not IRE values as digital video does not have IRE as IRE is an analogue voltage.

So yes, you've been editing in your own world making incompatible DV tapes in the procecss, that will also be of lower quality as they're using less code values to store the legal picture range.

Because it's digital video, you cannot tell FCP to handle blacks differently as it's handling them correctly to begin with. All you can do with your non-standard DV tapes is to use a proc amp or levels filter on them to get you blacks back down to 0% in FCP and work from there.

Also, why are you not using the FCP easy preset for advanced pulldown removal - there should be no need for a journey to cinema tools in your workflow??

Graeme
 
Thanks Graeme,
I arrived at this workflow because I was always encountering problems with remove advanced pulldown during capture. I would get warnings about a break in cadence or I would be editing in a 24p timeline and see interlaced frames. I just figured this way I have a 24p framerate file that is smaller and I know for sure is showing me the correct frames. It's funny you responded to this post, I was just making an ntsc to pal conversion down at my office with your filter, it works great, although quite a bit of render time.
Aron
 
Thanks - I know render time is an issue, but it still works out better than the alternatives. Hope you got your 7.5IRE setup issues sorted!

Graeme
 
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