View Full Version : optura xi zebra levels


Tony Hall
January 14th, 2005, 01:52 PM
I'm assuming that the Optura XI's zebra levels are set to 100%, but it also looks like it could be 90% on the viewfinder. Does anybody know for sure?

Xander Christ
January 14th, 2005, 05:55 PM
I've talked to Canon about this and the support technician wasn't able to answer the question, but he was certain that it was 100 to 110 IREs. I told him that wasn't broadcast standards, and he said that's all the information he had available to him.

Tony Hall
January 15th, 2005, 12:30 AM
Huh, well DV doesn't even have IRE's so he must have just meant that it was everything above 100... which is everything that's getting clipped.

Xander Christ
January 15th, 2005, 01:51 AM
DV does have IREs. I use my waveform all the time to monitor them. The DV spec has 0 to 100 IRE as the range. Ancient component analog's spec had 7.5 to 100 IREs. Old school video engineers still won't broadcast stuff with footage containing <7.5 or >100 IRE. And if they compress DV's IREs for analog broadcast it makes the video footage look even worse!!!

I watched the new Battlestar Galactica on SciFi this evening for the first time, and noticed that they have a lot of issues with highlights being blown... Really distracted me. They should use a waveform monitor to correct that, but I don't know what specs HD uses... yet.

Tony Hall
January 15th, 2005, 02:39 AM
Someone that's a bit more knowledgable should come along and explain this for me, but IRE's are an analog measurment. If you're using an analog waveform monitor, you're only measuring your camcorder's analog output, not what's recorded to tape. DV Rack has a digital waveform monitor and I believe it just goes on percentages of lumanence (sp?) from light to dark. Since DV doesn't have any "setup", the footage is equivilent to 0 IRE. It's hard to explain, but IRE's are analog and need not be a part of the digital workflow.

Tony Hall
January 15th, 2005, 10:21 AM
Oh and I also was wondering what size increments the exposure compensation steps up and down with. There's 11 steps, so are they .3 or .5 stops? Not that important, but inquiring minds want to know.

Xander Christ
January 15th, 2005, 12:36 PM
I don't have Serious Magic's DV Rack software, so I don't know anything about it. I do use the S-video out on most camcorders to monitor levels on the waveform. What's recorded to tape is really similar to what's coming out of the s-video port. On the Xi, the s-video port allows me to see how much "gain" there is since there is no control over it (damn you, Canon). Because Zebras can't be modified, the waveform helps me with lighting setup. As long as my signals aren't above 100IRE, I'm confident what's recorded to tape isn't above 100IRE either. I use the wavefrom monitor/RGB Parade/Vectorscope displays in Final Cut and Premiere Pro to assist with color correction, making sure I don't create illegal colors for broadcast purposes. Again, I don't know if digital television makes IREs obsolete, but we don't use digital television signals just yet... everything is still analog.

About the exposure compensation on the Xi, I haven't done anything to determine what each click is. I've been using aperture priority, locking the camera to f/1.9, hitting exposure lock to stop the shutter speed from changing, and then I use ND filters to control exposure. With all my glass filters, I have approximately 8 stops control in 1/2 stop increments.

Tony Hall
January 16th, 2005, 09:46 AM
That sounds like a pretty good way to do it.