dcp and leaders

Posted by Anonymous User 
Anonymous User
dcp and leaders
September 24, 2015 11:23AM
about to make my first dcp using opendcp and a question occurs: is there a protocol for coutdown? slate? bars?

what are the conventions regarding these things or are they simply omitted, assuming that, by this point, things should be standardized?

any guidance is much appreciated.

Re: dcp and leaders
September 24, 2015 03:16PM
they are not included on the video file.
slate and other info is contained in metadata.

Anonymous User
Re: dcp and leaders
September 24, 2015 03:44PM
thanks nick!

i get it about the slate info but is there no need for countdown or preroll? and, if i do need to use countdown and it's not part of the video file, how is that handled? sorry but first time with dcp.

thanks again,
Re: dcp and leaders
September 24, 2015 09:00PM
BabaG: I don't get it. If you want the countdown leader to be projected then include it at the beginning of the DCP. If you don't want the countdown leader to be projected then what do you want it for? Countdown leaders had a function in cinema projection.
How Movies Work by Bruce F. Kawin, p. 126
At the head of each reel is a strip of film with numbers that count down, usually to 3, called the head leader. From the start of the countdown to the first frame of picture is a distance of 12 feet (in 35mm). The last few feet of the head leader are opaque. By the time the reel being shown (call it Reel A) is nearly over, Reel B has been loaded into the other projector, perhaps with the head leader's "7" or "9" in the gate (that is, in projection position). Upon seeing the final changeover mark, the projectionist turns on the motor of Projector B. The two marks are separated by a distance of 11 feet, and in that interval, Projector B has time to get up to speed. (Knowing the projector intimately, the projectionist has learned which number to start from.) Upon seeing the second changeover mark, which ends 20 frames from the last frame of Reel A (after which comes the tail leader), the projectionist has just under a second to switch on the lamp in Projector B and to switch off the lamp in Projector A (or, leaving both lamps on, to block one beam and unblock the other).
They have no function in digital cinema.

Concerning color bars, DCPs are absolutely standardized as to color. Where the pixel in the frame in the .mxf has a certain X',Y',Z', the DCP projector must project X=X'^2.6, Y=Y'^2.6, Z=Z'^2.6 on the screen, scaled with brightness of the projection. It's too late to adjust the projection color with color bars after the DCP is made. However, you might be curious whether you've made a DCP with colors matching the colors you made in your video. I use video calibration test frames that I've posted before. With a calibrated monitor (including the player and the computer in the calibration) these frames make their X,Y,Zs. If you make a DCP from these test frames, using the same settings as your movie DCP, you can then examine the X',Y',Z's in the .mxf and compute what X,Y,Zs a DCP projector will make from them. There's no need to take your DCP to a friendly theater and aim your colorimeter at their screen, although I've done that. The colors are in the DCP.

The key to getting right colors from your DCP is really knowing how you viewed your video -- what it is and how it was played and displayed -- and then telling the DCP-making program those details, so the program can "view" the video in the same way.

Dennis Couzin
Berlin, Germany
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