Color bars at beginning of tape? at DVinfo.net

Josh Bass · January 30th, 2003, 03:09 PM

Just wondering, how long (if at all) do you put color bars at the beginning of new tapes when shooting? I was taught to do this when recording SVHS, as the first minute of the tape was unreliable. I still do it with DV, but I'm wondering if I'm cheating myself out of one last glorious minute of possible tape.

Robert Knecht Schmidt · January 30th, 2003, 03:25 PM

You may be cheating yourself; without having done a statistical analysis of any sort to verify, my experiences tell me dropout may occur in the middle of a MiniDV tape as frequently as it will the beginning. Has anyone done a more thorough study?

Jeff Donald · January 30th, 2003, 03:50 PM

Tape manufactures suggest that more dropouts will occur at the beginning and ends of tapes because of the manufacturing process (cutting, splicing, attaching to reels etc.) The inner portion of the tape is wound at a much smaller angle, stressing the tape more than the outer portion. The outer portion is more exposed to the elements and possible contamination from environmental causes (dust, lint etc.).

Bill Pryor · January 30th, 2003, 06:59 PM

Most dropouts experienced in the old days of 3/4" happened at the beginning and end of tapes; same with Betacam, though never as bad. I haven't seen a dropout in 2 years of DVCAM tapes, but I always put a minute of bars at the head and at least that much rundown at the tail. Tape is the cheapest thing of any shoot--why push the limits? Anyway, you need space at the head of the tape. Professional decks require some preroll, and it's a real pain to try to capture footage from the very beginning of a tape; you can't get it all. Also, if the time code shifts and you expect the very beginning of a shot on down in the tape to be used, that's a pain too. It's easy to be professional when you shoot and have rundown at the head and tail of each shot. If you're just doing home movies, then it's not a problem and don't worry about it.

Josh Bass · January 31st, 2003, 02:44 AM

This is for professional applications. Thanks guys.

Chris Hurd · January 31st, 2003, 06:27 AM

Color bars at the front of the tape are primarily intended for monitor calibration. I believe the standard length is sixty seconds. Normally there's a 60khz tone with 'em on the audio track. Bill Pryor would know much more about this than I do, however.

Jeff Donald · January 31st, 2003, 06:40 AM

When I used to prepare tapes for broadcast, this is how it was done.

Timecode starts at 23:58:30;00

15 seconds of black

60 seconds of bars and tone

10 seconds of slate and countdown

5 seconds of black

program starts at exactely 00:00:00;00

That way the timecode was also the total run time (TRT).

Some stations wanted the 5 seconds of black so it could be worked into their cart machines or edited etc.

Some stations wanted the timecode to start at

01:00:00;00

so we would just bump everything up 1 hour.

Jon Eriksson · January 31st, 2003, 07:38 AM

The bars and tone in the beginning of the tape is for either moniotor calibration, as Chris stated, or in post to detemine colour values and audio levels. I work as an editor and I always check the bars in the beginning to make sure they are set to legal values. Every camera/tape vary - if ever so slightly - and balansing them out before capturing saves hours of colour correcting.

So I would say the bars are vital as a reference point and should always be recorded if you want to be able to take you footage anywhere.

I hope this helps.

Regards
Jon

Bill Pryor · January 31st, 2003, 09:34 AM

Yep, bars and tone are for calibration, and it helps to have 60 seconds because sometimes you may need that much to get things tweaked properly. But the rundown also serves to not use the head and tail of the tape, where dropouts seem to occur more often. So even if you're shooting for your own use, it's a good idea. As Jon said, the editor checks every tape (or should), because every camera can vary a bit.

Nathan Gifford · January 31st, 2003, 09:59 AM

Chris it can't be 60 KHz audio unless dogs are doing the sound ;-)

Jeff Donald · January 31st, 2003, 10:06 AM

That should be 1KHz 0dB for the tone.

Jon Eriksson · January 31st, 2003, 10:17 AM

It used to be 1khz 0db, but since the switch to digital where audio cuts out at 0db, it should be set to -20db in the NTSC world and -18 for PAL users, but I believe this has been discussed in another thread if anyone is interested.

Jon

Jeff Donald · January 31st, 2003, 10:36 AM

Good comment, but I'm not sure of the answer. I think it depends on what format your working with. Most stations in the states still prefer Beta SP for broadcast and even though the source is digital the edited master is analog and get tone at 0dB. I've sent mini DV tapes out recently to a station with 0dB tone also and nothing was said. I think I'll check a couple of sources and see if I can get a consensus for NTSC.

Chris Hurd · January 31st, 2003, 11:41 PM

Don't know where I got 60khz... my Rottweiler can hear that, I guess... thanks for setting me straight!

;-)

Bill Markel · February 1st, 2003, 12:05 AM

-12db digital = 0db analog. If you look at the XL1s audio meters, the 12 is in a solid block. That block is the visual reference for what we know as 0db in the analog world. I didn't realize this at until I returned home after my 1st shoots with some very hot audio. If you play "B & T" in FCP, the tone plays at -12. If you lay off bars and tone to the camera from FCP, the tone registers at -12.

Bill

January 30th, 2003, 03:09 PM	#1
Josh Bass Slash Rules! Join Date: Apr 2002 Location: Houston, Texas Posts: 5,472	Color bars at beginning of tape? Just wondering, how long (if at all) do you put color bars at the beginning of new tapes when shooting? I was taught to do this when recording SVHS, as the first minute of the tape was unreliable. I still do it with DV, but I'm wondering if I'm cheating myself out of one last glorious minute of possible tape. __________________ The Bass' camerawork The Bass on IMDB

January 30th, 2003, 03:25 PM	#2
Robert Knecht Schmidt Wrangler Join Date: Feb 2002 Location: Cleveland, Ohio Posts: 1,933	You may be cheating yourself; without having done a statistical analysis of any sort to verify, my experiences tell me dropout may occur in the middle of a MiniDV tape as frequently as it will the beginning. Has anyone done a more thorough study? __________________ All the best, Robert K S Search DVinfo.net for quick answers \| The best in the business: DVinfo.net sponsors

January 30th, 2003, 03:50 PM	#3
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	Tape manufactures suggest that more dropouts will occur at the beginning and ends of tapes because of the manufacturing process (cutting, splicing, attaching to reels etc.) The inner portion of the tape is wound at a much smaller angle, stressing the tape more than the outer portion. The outer portion is more exposed to the elements and possible contamination from environmental causes (dust, lint etc.). __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

January 31st, 2003, 02:44 AM	#5
Josh Bass Slash Rules! Join Date: Apr 2002 Location: Houston, Texas Posts: 5,472	This is for professional applications. Thanks guys. __________________ The Bass' camerawork The Bass on IMDB

January 31st, 2003, 06:27 AM	#6
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,366 Images: 513	Color bars at the front of the tape are primarily intended for monitor calibration. I believe the standard length is sixty seconds. Normally there's a 60khz tone with 'em on the audio track. Bill Pryor would know much more about this than I do, however. __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

January 30th, 2003, 06:59 PM	#4
Bill Pryor Contributor Join Date: Jan 2003 Location: Kansas City, MO Posts: 4,449	Most dropouts experienced in the old days of 3/4" happened at the beginning and end of tapes; same with Betacam, though never as bad. I haven't seen a dropout in 2 years of DVCAM tapes, but I always put a minute of bars at the head and at least that much rundown at the tail. Tape is the cheapest thing of any shoot--why push the limits? Anyway, you need space at the head of the tape. Professional decks require some preroll, and it's a real pain to try to capture footage from the very beginning of a tape; you can't get it all. Also, if the time code shifts and you expect the very beginning of a shot on down in the tape to be used, that's a pain too. It's easy to be professional when you shoot and have rundown at the head and tail of each shot. If you're just doing home movies, then it's not a problem and don't worry about it.

January 31st, 2003, 06:40 AM	#7
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	When I used to prepare tapes for broadcast, this is how it was done. Timecode starts at 23:58:30;00 15 seconds of black 60 seconds of bars and tone 10 seconds of slate and countdown 5 seconds of black program starts at exactely 00:00:00;00 That way the timecode was also the total run time (TRT). Some stations wanted the 5 seconds of black so it could be worked into their cart machines or edited etc. Some stations wanted the timecode to start at 01:00:00;00 so we would just bump everything up 1 hour. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

January 31st, 2003, 07:38 AM	#8
Jon Eriksson Regular Crew Join Date: Aug 2002 Location: London, UK Posts: 42	The bars and tone in the beginning of the tape is for either moniotor calibration, as Chris stated, or in post to detemine colour values and audio levels. I work as an editor and I always check the bars in the beginning to make sure they are set to legal values. Every camera/tape vary - if ever so slightly - and balansing them out before capturing saves hours of colour correcting. So I would say the bars are vital as a reference point and should always be recorded if you want to be able to take you footage anywhere. I hope this helps. Regards Jon __________________ Real Men do not Preview

January 31st, 2003, 09:34 AM	#9
Bill Pryor Contributor Join Date: Jan 2003 Location: Kansas City, MO Posts: 4,449	Yep, bars and tone are for calibration, and it helps to have 60 seconds because sometimes you may need that much to get things tweaked properly. But the rundown also serves to not use the head and tail of the tape, where dropouts seem to occur more often. So even if you're shooting for your own use, it's a good idea. As Jon said, the editor checks every tape (or should), because every camera can vary a bit.

January 31st, 2003, 09:59 AM	#10
Nathan Gifford Wrangler Join Date: Sep 2001 Location: Tickfaw, LA Posts: 1,217	Chris it can't be 60 KHz audio unless dogs are doing the sound ;-) __________________ Nathan Gifford Southern Cyclist Magazine & Productions For quick answers try our Search! To see me and Rob Lohman click here

January 31st, 2003, 10:06 AM	#11
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	That should be 1KHz 0dB for the tone. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

January 31st, 2003, 10:17 AM	#12
Jon Eriksson Regular Crew Join Date: Aug 2002 Location: London, UK Posts: 42	It used to be 1khz 0db, but since the switch to digital where audio cuts out at 0db, it should be set to -20db in the NTSC world and -18 for PAL users, but I believe this has been discussed in another thread if anyone is interested. Jon __________________ Real Men do not Preview

January 31st, 2003, 10:36 AM	#13
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	Good comment, but I'm not sure of the answer. I think it depends on what format your working with. Most stations in the states still prefer Beta SP for broadcast and even though the source is digital the edited master is analog and get tone at 0dB. I've sent mini DV tapes out recently to a station with 0dB tone also and nothing was said. I think I'll check a couple of sources and see if I can get a consensus for NTSC. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

January 31st, 2003, 11:41 PM	#14
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,366 Images: 513	Don't know where I got 60khz... my Rottweiler can hear that, I guess... thanks for setting me straight! ;-) __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

February 1st, 2003, 12:05 AM	#15
Bill Markel Regular Crew Join Date: Jan 2002 Location: Sicklerville, NJ Posts: 59	Digital audio has different levels -12db digital = 0db analog. If you look at the XL1s audio meters, the 12 is in a solid block. That block is the visual reference for what we know as 0db in the analog world. I didn't realize this at until I returned home after my 1st shoots with some very hot audio. If you play "B & T" in FCP, the tone plays at -12. If you lay off bars and tone to the camera from FCP, the tone registers at -12. Bill