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Thread: Auto Calibration for sources

  1. #16
    Registered User ted's Avatar
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    The purpose of the calibration as I see it is to calibrate the signal from the far end of the cable all the way through the Tricaster. Thus matching for differences in types of inputs, timing the sources and getting a solid reference to color match. You have color correction to match the actual camera image.
    White balance is different, but in practical terms, if you use the same white card and balance each camera from differenet angles, i.e. their set location, you can get undesired results. I was surprised the first time I had this happen. This would be one thing to be aware of if you do use the camera on a color chart.

    I agree with you that it would be best to calibrate the actual camera image. If you brought all cameras side by side and Autocalibrated on the same card you would in theory have the best calibration.

    I tried to find professional 100% color bar charts for months with no luck. I even tried talking one of the manufacturers at NAB into making one. I think it was Vertek. They were interested, but didn't know if there would be enough demand. If I see them this year I'll tell them you and I would buy one!

    Remember, all this is JMHO. Based on 30 years of Broadcast experience, but that doesn't mean it's totally accurate.
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  2. #17
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    Hi ted,

    thank you for answering my question.

    It makes totally sense to compensate the quality loss of the (mostly) long cables to the Tricaster. Maybe it's because I work only with SDI connections that I don't had that in mind.

    In professional broadcasting situations it is exactly like i described: Framing all cameras on a color plate and then using the CCUs to tweak them that they look equal.

    I remember in the old days with valve based cameras (don't know if that is the right word) f.e. "Plumbicon" someone standing there with a little screwdriver (for 2 hours or so) doing a calibration straight in the camera. It was a really long procedure.

    Regards

    Pro

  3. #18
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    Use Same-Length Video Out Cables from Cameras, to TriCaster!

    Quote Originally Posted by ted View Post
    The purpose of the calibration as I see it is to calibrate the signal from the far end of the cable all the way through the Tricaster. Thus matching for differences in types of inputs, timing the sources and getting a solid reference to color match. You have color correction to match the actual camera image.
    White balance is different, but in practical terms, if you use the same white card and balance each camera from differenet angles, i.e. their set location, you can get undesired results....

    I agree with you that it would be best to calibrate the actual camera image. If you brought all cameras side by side and Autocalibrated on the same card you would in theory have the best calibration.
    I suppose we'd also to well to alert any newbies on this subject, to the fact that it's sometimes tempting to discard the fact that you ought to ensure that all the video output cable from all the cameras inputting a signal to TriCaster, are of equal length, for better ease and accuracy in color phase/hue calibration.

    Else, it's quite likely that some camera(s) might be utterly difficult to properly match up with other(s), due to an extreme phase incoherency caused by the excessive difference in signal delay, along various cable lengths.

    Strive for excellence in camera matching at the outset (beginning with same-length camera cable); for in some cases, the undesirable result might present an insurmountable challenge to fix in post-production (editing).
    Last edited by Quiet1onTheSet; 02-26-2009 at 12:33 PM.

  4. #19
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    Quote Originally Posted by pro---studio View Post
    Hi ted,

    thank you for answering my question.



    I remember in the old days with valve based cameras (don't know if that is the right word) f.e. "Plumbicon" someone standing there with a little screwdriver (for 2 hours or so) doing a calibration straight in the camera. It was a really long procedure.

    Regards

    Pro
    Oh, yeah, the vacuum tube cameras!

  5. #20
    Registered User NRBC_Media's Avatar
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    DSC Labs makes color charts. I bought my last set from Filmtools.com for my day job. Still have to tweak some Thomson LDK20's and their chart works great.

    However at the church, where my Tricaster resides, I just use a white card at stage center so all cameras can shoot, set Iris to same level on all cams by waveform, then AWB. So far my cams have been close enough for the waveform/vectorscope and my eye. As they age, it may change.

    The Tricaster Calibrate feature is for cable compensation, ie luminance and chroma level, not necessarily related to WB or BB.

  6. #21
    Registered User ted's Avatar
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    Quote Originally Posted by Quiet1onTheSet View Post
    I suppose we'd also to well to alert any newbies on this subject, to the fact that it's sometimes tempting to discard the fact that you ought to [COLOR="Orange"] ensure that all the video output cable from all the cameras inputting a signal to TriCaster, are of equal length, for better ease and accuracy in color phase/hue calibration.
    I "think" cable length differences are one of the things calibration takes care of as mentioned in my earlier post. But I could be wrong.
    Ted R. Ruiz Sr.
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  7. #22
    Registered User ted's Avatar
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    Quote Originally Posted by NRBC_Media View Post
    DSC Labs makes color charts. I bought my last set from Filmtools.com for my day job.
    What we were talking about is an actual 100% Color Bar chart. One that exactly matches the 100% color bars from most cameras.
    This would likely improve the calibration since you are actually using the "Cameras" electronics to calibrate from. At least in theory "according to Ted". I would love for NewTek to respond since they know the facts behind TriCasters calibration.

    I didn't find anything like this on Filmtools.com.
    Ted R. Ruiz Sr.
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  8. #23
    Registered User NRBC_Media's Avatar
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    The charts I spoke of will do that.
    Here is a link for a cheaper one.
    http://www.filmtools.com/accu-chart-...reference.html

    **I am not affiliated with vendor or manufacturer.**
    Last edited by NRBC_Media; 02-27-2009 at 11:17 AM.

  9. #24
    Registered User ted's Avatar
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    Quote Originally Posted by NRBC_Media View Post
    **I am not affiliated with vendor or manufacturer.**
    It's obvious you are only trying to help with a resource.

    Now for the "however".
    This isn't a 100% color bar chart as NewTek recomends from the source for auto cal.

    In fact it reads the following...
    the chart is a neutral background of approximately 50% reflectance.
    AND...
    The chart ... is not intended to produce a display on a vectorscope corresponding to an electronically generated color bar signal.

    So no, this isn't what we are talking about or is needed.
    I think I might spend a few bucks and create our own, have a bunch printed professionally and sell them.
    I can't believe how much they charge for these things.
    Ted R. Ruiz Sr.
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  10. #25
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    Pro - I've had this thought myself - from shooting in college and throughout my career.

    With consumer or "prosumer" cameras, you are right. It makes very little sense or difference if you use each individual camera's color bar generator.

    Where it can make a small difference is when you use cameras of the same make and model, but for whatever reason have differing output signatures. Perhaps a not-do-good capacitor that are a few farads off, coloring due to wiring, or an impure conductor from different batches of metal. In modern electronics and signal processing, however - it is unlikely you will see much difference.

    More helpful would be if you had a number different cameras with a mix in makes and models. Here you could get a good baseline reference of what each camera thinks is a SMPTE pattern and adjust accordingly.

    Where the autocalibration feature IS very useful is with broadcast cameras. For example, I use 20-year-old dockable broadcast cameras that can adjust their output in the head, back, or CCU. Or a combination of all three. So you can color the output in several different ways - even with the same setting of white balance, pedestal, shutter, and filter.

    Also, due to the age - the electronics can color the signal as well (yes, yes, yes - I can constantly adjust and calibrate all my cameras over time - but why bother?). When you can simply PRESS THE MAGIC BUTTON!

    Yes, the bars change depending on the settings at the head-back-ccu, so making sure those line up are essential.

    Now... what you desire is likely a giant SMPTE bar color poster that you can hold in front of all your cameras so you can calibrate off of the signal coming through the lens, so to speak.

    Or you could just white balance.
    Sandy Audio Visual LLC
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  11. #26
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    Smpte bars

    Here's a very good tutorial on how to use bars for your monitor.

    Ted - the reason you likely didn't find SMPTE bars in paper form are because they were never designed to be used that way.

    The tutorial link below should have a link to the obit of the guy who created the bars. It's a good history lesson. You're probably heard it before but forgot given your 30 years in the field!

    http://www.videouniversity.com/tvbars2.htm

    Colin
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  12. #27
    Registered User ted's Avatar
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    Quote Originally Posted by csandy View Post
    Ted - the reason you likely didn't find SMPTE bars in paper form are because they were never designed to be used that way.
    Colin
    But when Color Bars were invented, they didn't know about Tim Jenison or NewTek.
    Ted R. Ruiz Sr.
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  13. #28
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    How true!:agree:
    Sandy Audio Visual LLC
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    My opinion, uncensored. The blog at www.sandyaudiovisual.com.

  14. #29
    NewTek System Integrator PIZAZZ's Avatar
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    Simple solution we found in the past to assist in calibrating cameras with the VT/TriCaster, lay off a few DV tapes of bars and tone. Play that tape back in the camera in order to do the auto calibration. This was especially useful for the Canon XL1 back in the day because if you knew the secret to display bars, well they were not SMPTE standard bars.

    From what I understand, the calibration in TriCaster and VT are more so to equalize the cable lengths not to adjust final video quality. You can have all the cameras calibrated to bars and still each camera look different because their white balance is off.

    Order of Procedure for us:

    Put cameras on bars
    Calibrate each input in TC
    Then focus cameras to stage or central area
    White Balance each camera with something white large enough to fill the screen of the camera the furthest away.
    COMPARE each camera for final quality test
    Tweak Proc Amps if needed.

    BTW a handy horizontal wipe helps greatly to sync cameras if you are having problems. Put your reference camera on top and the one you want to adjust on bottom. Wipe halfway. (H on a TriCaster keyboard shortcut)

    After all of this is done, pray that someone doesn't drastically change your lighting.
    If someone touches your lighting, beat them down with a large bat.
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  15. #30
    NewTek System Integrator PIZAZZ's Avatar
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    Quote Originally Posted by Quiet1onTheSet View Post
    I suppose we'd also to well to alert any newbies on this subject, to the fact that it's sometimes tempting to discard the fact that you ought to ensure that all the video output cable from all the cameras inputting a signal to TriCaster, are of equal length, for better ease and accuracy in color phase/hue calibration.

    Else, it's quite likely that some camera(s) might be utterly difficult to properly match up with other(s), due to an extreme phase incoherency caused by the excessive difference in signal delay, along various cable lengths.

    Strive for excellence in camera matching at the outset (beginning with same-length camera cable); for in some cases, the undesirable result might present an insurmountable challenge to fix in post-production (editing).
    Peter's suggestion to always use the same length cable is not realistic.

    The kits we built for the NCAA had 100, 250, and 500' runs of cable. It would be ridiculous to use 500' of cable if 100' works just the same.

    The calibration tools/Proc Amp in TriCaster are there to assist us with the varying cable lengths. Copper is expensive. Shipping is worse.
    Last edited by PIZAZZ; 03-01-2009 at 04:39 PM.
    Jef Kethley
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    Using:
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    Panasonic UB300 4k cams
    Tactical Fiber/converters, SDI2NDI converters, NDI-Viewfinder, and NDI2HDMI

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