Why are .MXF Histograms so Wide?

MH_Stevens wrote on 2/3/2008, 8:33 PM

After capturing some mpeg4 files converted to .mxf files into Vegas out of the EX1 I'm surprised (pleasantly) at how the dynamic range is wider than the Vegas vectorscope! I have some clips that spread from -10 to 110%. Anyone like to explain or comment?

Comments

GlennChan wrote on 2/3/2008, 9:23 PM

Is the studio RGB box checked in your Video Scopes settings? (In 32-bit mode the footage might decode to computer RGB levels, so you'd want that box unchecked.)

2- I believe it's legal for colors to be that far out... but not legal if you have to convert that to composite (e.g. composite NTSC).

MH_Stevens wrote on 2/4/2008, 7:17 AM

Yes. Studio RGB is UNchecked. I'm using 32bit and computer RGB. My mmxf histograms from the EX1 are at least 25% wider than .m2t from the FX1 showed.

farss wrote on 2/4/2008, 8:58 PM

Just checked this with some charts we shot.
With the Vegas scopes in Computer RGB it sure goes to 100%.
Switching to 32bit Gamms 2.2 it looks like there's significant clipping both on the preview monitor and in the scopes. The fine details in the res chart just vanish.
However it seems it's not being lost, applying the levels filter with out =0.92 the detail is back. Scopes still read white at 100% but the top end now looks the same as it did in 8 bit.

Bob.

MH_Stevens wrote on 2/4/2008, 9:07 PM

Bob: Look at what I wrote on the DVi forum under "abrupt clipping..." thread. I have now cut back my exposure levels with EX1 and getting much better results.

rmack350 wrote on 2/4/2008, 9:26 PM

Funny, I was just reading a description of this in Stu Maschwitz DV Rebel book. Starts on pg 233 if you've got the book.

Rob Mack