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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » Curious about DA-20 error readings (Page 1)

 
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Author Topic: Curious about DA-20 error readings
Jack Ondracek
Film God

Posts: 2301
From: Port Orchard, WA, USA
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 - posted 04-09-2006 01:07 PM      Profile for Jack Ondracek   Author's Homepage   Email Jack Ondracek   Send New Private Message       Edit/Delete Post 
How is it that a trailer... probably printed from the tail end of some film roll, will show error rates of 0 or 1, yet some brand-new features will never drop below 5?

We're running XLs, top-mounted reader, dedicated Kelmar/Filmguard on each screen (pictures on our web site).

Having scoped everything, and verified all parameters per the book, I'm assuming the good rates on the trailer roll indicate good alignment. Bad assumption?... or what?

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Louis Bornwasser
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From: prospect ky usa
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 - posted 04-09-2006 02:19 PM      Profile for Louis Bornwasser   Author's Homepage   Email Louis Bornwasser   Send New Private Message       Edit/Delete Post 
Low readings indicate that the film involved happens to agree with your reader. It is entirely possible to be "out" slightly and have an also appropriately "out" film. It is therefore necessary to be in the center of "normal." That is why it is always necessary tol use verified good test loops instead of just any film, which could be almost out-of-tolerance. Louis

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Jack Ondracek
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From: Port Orchard, WA, USA
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 - posted 04-09-2006 06:10 PM      Profile for Jack Ondracek   Author's Homepage   Email Jack Ondracek   Send New Private Message       Edit/Delete Post 
Makes sense to me. I got a bunch of new Dolby test film through Vern... enough to make several loops. I've seen the comments here about Dolby being less accurate than NT... did that include the digital stuff, too?

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Louis Bornwasser
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 - posted 04-09-2006 06:53 PM      Profile for Louis Bornwasser   Author's Homepage   Email Louis Bornwasser   Send New Private Message       Edit/Delete Post 
Jack; the DIGITAL loops are double-checked at Dolby so they should be OK. Louis

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John Hawkinson
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From: Cambridge, MA, USA
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 - posted 04-09-2006 06:59 PM      Profile for John Hawkinson   Author's Homepage   Email John Hawkinson   Send New Private Message       Edit/Delete Post 
Brad Miller suggests (in a thread long ago I cannot find) that you should use a bunch of trailers from the major labs (Deluxe and Technicolor, multiple locations). That way, assuming that the trailers are printed on equipment calibrated the same as features (or even the same equipment), you're pretty much guaranteed to be right.

It makes sense to me. Why rely on a test film to be at some standard when you can adjust empirically for what is really correct?

Of course the labs have a harder calibration problem...

--jhawk

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Sam D. Chavez
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From: Martinez, CA USA
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 - posted 04-09-2006 09:12 PM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
The previews are typically made on a different production line is one possible reason. Others have noted the previews often look better than release prints as well.

As to test films, I believe the negative used to make Dolby test films used EC-9 software while the previews and features are using the current EC-11.

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Richard May
Phenomenal Film Handler

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From: Floral Park, NY USA
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 - posted 04-09-2006 09:22 PM      Profile for Richard May   Email Richard May   Send New Private Message       Edit/Delete Post 
I think Sam partially answered the question. I too have seen trailers run much cleaner in regards to low error rates than features do. Whats up with that??

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Monte L Fullmer
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From: Nampa, Idaho, USA
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 - posted 04-10-2006 04:06 AM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
..wondered about that as well - watching the display on a DA-20 when trailers are playing and with excellent error rate readings..then the splice to the feature and all of a sudden mid '5' to '6' then suddenly 'F' readings.....but the unit doesn't drop out of digital with this sudden flip-flopping (uh..oh .. hook up the laptop with the WinDRAS program installed and watch the jitter rate go crazy...have I got a goofy print..?)

-Monte

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

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From: Boston, MA
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 - posted 04-10-2006 05:53 AM      Profile for Michael Schaffer   Author's Homepage   Email Michael Schaffer   Send New Private Message       Edit/Delete Post 
quote: Sam D. Chavez
As to test films, I believe the negative used to make Dolby test films used EC-9 software while the previews and features are using the current EC-11.
Could you elaborate on that a little? What is EC-...? Why would different encoding software (if that's what it is) cause different error rates on printed stock?

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John Hawkinson
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 - posted 04-10-2006 10:04 AM      Profile for John Hawkinson   Author's Homepage   Email John Hawkinson   Send New Private Message       Edit/Delete Post 
Well, Monte, the jitter rate is really independent of calibration. So if you have a print with a high jitter rate, it's definitely a characteristic of print.

--jhawk

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Gordon McLeod
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 - posted 04-10-2006 10:08 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
Using a trailer is all well and good but a reference is a reference and I have found typically it is best to rely on standardized test films

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Sam D. Chavez
Film God

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 - posted 04-10-2006 10:29 AM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
I forget what the EC actually means. The 9 and 11 refer to software revisions in the Dolby 5.1 encoder used in making the soundtrack. The higher error rate on test films does not have to do with the EC-9 or 11 specifically afaik, but the whole process of making a soundtrack has improved over time.

As Gordon says, the reference is the reference.

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John Hawkinson
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 - posted 04-10-2006 11:58 AM      Profile for John Hawkinson   Author's Homepage   Email John Hawkinson   Send New Private Message       Edit/Delete Post 
I think I wasn't so clear. The point of using trailers is not to use a trailer, but that you can use a WHOLE BUNCH of data points, and calibrate to the mean (because you have multiple trailers from each of the labs).

So you're not stuck calibrating to a single reference that might be slightly off. You shoot for the setting that makes the most of the trailers come out right, thus optimizing for the average of Deluxe Toronto, Deluxe Hollywood, Technicolor North Hollywood, and Technicolor Mirabel. With perhaps DuART and Technicolor New York thrown in for kicks [Smile]

(Of course, maybe I was clear and you still disagree -- that's fine [Smile] )

--jhawk

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Jack Ondracek
Film God

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From: Port Orchard, WA, USA
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 - posted 04-10-2006 12:18 PM      Profile for Jack Ondracek   Author's Homepage   Email Jack Ondracek   Send New Private Message       Edit/Delete Post 
I generally agree with Gordon's notion of relying on standards for system calibration. John's post also outlines what'll probably be necessary here. Unfortunately, for me, that feeling goes back to when you'd want a single standard reference for audio tape recording. Many of the stations I worked for sent dubs out to other stations, and having my equipment GENERATING product as close to NAB standards as possible was always my goal.

On the other hand, if after using a known standard on my PLAYBACK equipment, I get great readings on some media, and lousy readings on others, I can see the point for compromise. Going back to my radio days, we had a bunch of Ampex PR-10 machines that had thumbscrews so that you could fine-tune playback head azimuth. It made a big difference for us... especially when receiving dubs from other stations! [Smile]

Back to the booth here... IF such a compromise resulted in overall error rates around, say, 3... maybe 4 tops I'd be much happier with the system as a whole.

I have to admit though, knowing my system might have to be "off" in order to play everything "OK", does bother me a bit. It seems that the error rates were more consistent, back 2 or 3 years ago... but maybe I'm just imagining that.

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
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 - posted 04-10-2006 05:29 PM      Profile for Michael Schaffer   Author's Homepage   Email Michael Schaffer   Send New Private Message       Edit/Delete Post 
quote: Sam D. Chavez
The higher error rate on test films does not have to do with the EC-9 or 11 specifically afaik, but the whole process of making a soundtrack has improved over time.
I guess that must have something to do with better error correction and data redundancy then since I don't see how the physical properties of the printed track would be improved by improving the encoding software?

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