What are 108% white ? at DVinfo.net

Peter Rixner · June 17th, 2009, 02:52 AM

Hi :)

when calibrating my light meter I found that the built-in spot meter of the EX1 shows 108% when completely white. 108% not 100%.

Further I found, that when importing EX1 clips to the Adobe Premiere timeline I also get more than a 100% on the waveform monitor. A pure white is normally 100% there.

But even better:
There is real information in that misterious 8%. I had a shot whith snow-covered mountains that showed clearly more information than when I limit the footage to 100%.

My next problem is how to keep that information. As soon as it's rendered out it clips to 100% :(
But that's probably for a Premiere Pro forum.

So: Is there more than the usual 8-Bit. Maybe 8.5 :)

Thanks for and ideas!

Peter

David C. Williams · June 17th, 2009, 03:32 AM

Broadcast legal is 16-235, or 100% in analogue in most countries. The EX can use the full 255 for 109% which now works for some HD delivery formats.

Peter Rixner · June 17th, 2009, 07:47 AM

Are You sure ?

I can switch my Matrox Card to broadcastsafe and that reduces the whites from 100% to something little below. Or better to say from 1 to 0.95 or so.

So I would assume that 255 white = 100% or the Value 1.
Which it clearly is when I switch back from Broadcastsafe to "Post Production", which means full Range 0-255.

BUT the EX1 is above that 1.
But it's probably a interpretation thing.
I am of course aware, that it cannot be more than 8-Bit.

Anyone any more ideas ?

Thanks!

Peter

Bill Ravens · June 17th, 2009, 08:39 AM

hmmm...not sure why there is a mystery. Most HDV cams, these days, record superwhites(white to 109% IRE). The issue is how to handle these superwhites within the NLE because delivery NTSC and PAL displays limit the range to RGB16-235. Computer monitors can display full range 0-255, but, unless your delivery medium is the web, these values will be clipped to RGB16-235 by the delivery display unless you deal with this during color correction.

One way to deal with it is to just ignore the fact that values outside RGB16-235 will be clipped. A better way to deal with it is do apply a knee to the "levels curve" that smoothly blends the illegal values back into the RGB16-235 range. Note that some NLE's will automatically remap the color mapping to broadcast levels when you import your footage, so, you'll never know that your cam was recording 109% IRE. Each NLE has a different way for dealing with this issue, altho' the actual techniques are to either clip or blend with a knee.

Bob Grant · June 17th, 2009, 08:43 AM

Going to 108% simply means more of the range of digital values are used. For certain it can get clipped down the track however it's simple enough to use a curve to map the 100% to 108% values into the legal range.
Some of the Cine gamma curves in the EX produce 108% at 480%. What that means I'm pretty sure is that if you set exposure so that 100% white (e.g. white card) = 100% then clipping will occur for something 480% brighter than the white card e.g. a specular highlight. You can decide to clip that off or retain the superwhite or make use of it during compositing.

June 17th, 2009, 02:52 AM	#1
Peter Rixner Regular Crew Join Date: Mar 2005 Location: near Munich, Bavaria Posts: 139	What are 108% white ? Hi :) when calibrating my light meter I found that the built-in spot meter of the EX1 shows 108% when completely white. 108% not 100%. Further I found, that when importing EX1 clips to the Adobe Premiere timeline I also get more than a 100% on the waveform monitor. A pure white is normally 100% there. But even better: There is real information in that misterious 8%. I had a shot whith snow-covered mountains that showed clearly more information than when I limit the footage to 100%. My next problem is how to keep that information. As soon as it's rendered out it clips to 100% :( But that's probably for a Premiere Pro forum. So: Is there more than the usual 8-Bit. Maybe 8.5 :) Thanks for and ideas! Peter

June 17th, 2009, 03:32 AM	#2
David C. Williams Major Player Join Date: Jun 2008 Location: melb.vic.au Posts: 447	Broadcast legal is 16-235, or 100% in analogue in most countries. The EX can use the full 255 for 109% which now works for some HD delivery formats. __________________ www.davidwilliams.com.au

June 17th, 2009, 07:47 AM	#3
Peter Rixner Regular Crew Join Date: Mar 2005 Location: near Munich, Bavaria Posts: 139	Are You sure ? I can switch my Matrox Card to broadcastsafe and that reduces the whites from 100% to something little below. Or better to say from 1 to 0.95 or so. So I would assume that 255 white = 100% or the Value 1. Which it clearly is when I switch back from Broadcastsafe to "Post Production", which means full Range 0-255. BUT the EX1 is above that 1. But it's probably a interpretation thing. I am of course aware, that it cannot be more than 8-Bit. Anyone any more ideas ? Thanks! Peter

June 17th, 2009, 08:39 AM	#4
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	hmmm...not sure why there is a mystery. Most HDV cams, these days, record superwhites(white to 109% IRE). The issue is how to handle these superwhites within the NLE because delivery NTSC and PAL displays limit the range to RGB16-235. Computer monitors can display full range 0-255, but, unless your delivery medium is the web, these values will be clipped to RGB16-235 by the delivery display unless you deal with this during color correction. One way to deal with it is to just ignore the fact that values outside RGB16-235 will be clipped. A better way to deal with it is do apply a knee to the "levels curve" that smoothly blends the illegal values back into the RGB16-235 range. Note that some NLE's will automatically remap the color mapping to broadcast levels when you import your footage, so, you'll never know that your cam was recording 109% IRE. Each NLE has a different way for dealing with this issue, altho' the actual techniques are to either clip or blend with a knee.

June 17th, 2009, 08:43 AM	#5
Bob Grant Trustee Join Date: Nov 2005 Location: Sydney Australia Posts: 1,570	Going to 108% simply means more of the range of digital values are used. For certain it can get clipped down the track however it's simple enough to use a curve to map the 100% to 108% values into the legal range. Some of the Cine gamma curves in the EX produce 108% at 480%. What that means I'm pretty sure is that if you set exposure so that 100% white (e.g. white card) = 100% then clipping will occur for something 480% brighter than the white card e.g. a specular highlight. You can decide to clip that off or retain the superwhite or make use of it during compositing.