Film-Tech Forum ARCHIVE: Is the flat DTS 'Digital Experience' tag printed too high?

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Posted by Michael Barry (Member # 237) on 08-15-2000, 10:39 AM:

I noticed that when preceeding flat trailers are framed correctly, the 'This Theatre Features' line from the DTS tag is cropped from the top of the screen. To present a show correctly, I find it necessary to rack down for the DTS tag, then rack back up again once the feature starts...has anyone else noticed this or have a suggestion to overcome it? I remember talking to John Wilson about it...just wondering how endemic this is...ie. are overseas prints the same?

Posted by John Pytlak (Member # 331) on 08-15-2000, 11:25 AM:

You may be encountering prints which were printed on a bi-directional panel printer. Since the printing negative has BH perforations that are 0.073 inches high, and the print film has KS perforations that are 0.078 inches high, there can be a 0.005 inch vertical image shift, depending upon whether the film was printed heads-to-tails, or tails-to-heads. Of course, no shift occurs if the prints are always contact printed in the same direction.

If the shift is greater than this, there may be a problem with the positioning of the image on the printing negative that was supplied to the lab.

You can check the image position to see if it conforms to standard SMPTE 195, which says the image should be "within 0.012 inches" of the nominal horizontal centerline centered between perfs.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

Posted by John Walsh (Member # 168) on 08-15-2000, 11:29 AM:

You will need a length of alignment film, like SMPTE 35PA, to know for sure. I'm assuming you mean that it is way off, not just a little. If so, that's the best way. You could very accuratly measure the screen height and throw, and put that into the lens formula to see if you have the correct size lens. If you can't do that, you could use a micrometer to measure the aperture opening, but that's not very accurate.

One time a guy wanted us to run a 35mm short he had copied from a video source. While it was running, I noticed it was too high, but did not touch the framing knob, because I wanted him to know exactly how it was printed. Of course, he came into the booth telling me to frame up. I told him, OK, but at theaters with few or no operators, it would remain too high. We got into a slight arguement. Luckly, I just happened to have my SMPTE standards with me. First, I proved to him that theaters run 1.85 at 446 x 825. Then I threaded alignment film to prove the framing was correct.

He couldn't belive it. He asked if I could show the alignment film and his film at the same time. So, after warning him about possiable damage to his film (he didn't care) I threaded both a test loop and his film. We could measure how far off it had been printed.

Posted by Brad Miller (Member # 2) on 08-15-2000, 12:33 PM:

SMPTE PA-35 target film is NOT properly centered vertically. I've never seen a roll that was.

Either that or every other print I've ever ran was printed significantly out of frame.

Posted by Gordon McLeod (Member # 33) on 08-15-2000, 12:57 PM:

Well since SMPTE wrote the book so to say I think they are right
I believe the centreline is specified in reference to the perf

Posted by Brad Miller (Member # 2) on 08-15-2000, 01:03 PM:

Ok Gordon, go get your loop of PA35 and take it to a theater without excessive cropping. Run it and frame it absolutely perfectly. Then lock down the framing control and see how long it takes for you to get a nasty call about the films being out of frame.

Like I said, it's either the PA-35 is correct and EVERY other film ever printed is wrong, or everything else is correct and the PA-35 is wrong. Hmmmm, I'm not putting my money on SMPTE here. I can't be the only person who's ever noticed this.

PA-35 is great for setting things up and it IS printed perfectly centered left to right, but on every installation, the framing must be adjusted slightly to achieve perfect framing after the PA-35 loop has been in the projector. This was also true of RP-40 loops.

Posted by John Pytlak (Member # 331) on 08-15-2000, 02:02 PM:

Brad:

SMPTE Recommended Practice RP 40 specifies location on the film and tolerances for the 35-PA test film:

"The center of the test image shall be within +/- 0.001 in (0.03 mm) of the center of the projectable image area specified in ANSI/SMPTE 195. All projectable image area lines shall be within +/- 0.002 in (0.05 mm) of the nominal dimensions of the test image."

ANSI/SMPTE 195 specifies the horizontal centerline of the image to be exactly between two perforations, or a "nominally equal" distance between them.

So look at your 35-PA (RP 40) film under a measuring (toolmakers) microscope. The horizontal centerline of the 35-PA (RP 40) film should line up exactly between two perforations within 0.001 inches (0.03 mm). If it doesn't, it does not meet the SMPTE practice.

I just looked at a copy of 35-PA-200 that I bought from SMPTE late last year, and it appears to be "on the money" for vertical centering.

One possible reason for the vertical "shift" you see may be that SMPTE usually manufactures 35-PA on film perforated BH-1866, having a 0.073 inch perforation height, and 0.1866 inch perforation pitch. This is because many labs use it for optical printer line-up. Normal release prints are made on a contact printer, using film perforated KS-1870, with a 0.078 inch perforation height, and a 0.1870 pitch.

Are the framelines of the prints that are vertically shifted centered between two perfs? If not, the shift is in the print, and not the 35-PA test film.

Posted by Brad Miller (Member # 2) on 08-15-2000, 02:21 PM:

John, I haven't bothered to get out my microscope, but the fact remains that either the SMPTE film is off, or every release print is off. Go to a local theater that will let you into the booth to play for a few minutes and check it out for yourself.

Back in the late 80s/early 90s every Universal film was horribly "low" in framing. Why this affected only Universal prints is beyond me. Nothing else from the same lab suffered such problems. Now Universal prints are centered perfectly along with every other film (not counting the PA-35).

Sometimes it is hard to believe that a reference film could be off, but I've also got a Dolby tone loop that fluctuates violently up and down in amplitude. I'll have to scan that one in for ya. Still, just because the SMPTE film says your framer is centered does not mean you are projecting the print centered. Check it out for yourself.

Posted by John Pytlak (Member # 331) on 08-15-2000, 02:57 PM:

The image area defined by the standards can be seen and measured by looking at the print directly under a microscope. What we may be dealing with here is that the SMPTE 35-PA film is "on-standard", and most release prints are shifted because of the differences in pitch, hole size, and printing direction. No big deal, unless the shift varies reel-to-reel, or you are "locking" framing based solely on 35-PA.

Posted by Gordon McLeod (Member # 33) on 08-15-2000, 06:09 PM:

I would never lock a framer anyway in a non movable manner
There is enough risk of printer slipage especally if alternating reels get printed head tail vs tail head to have slight shifts and if the plates are could dead on then a problem might arise
I have never noticed any differance when comparing dailies to the 35PA

Posted by Steve Guttag (Member # 268) on 08-15-2000, 06:53 PM:

John,

I think you hit the nail on the head...the 35-PA test film is indeed centered (to a much higher tolerence than any release print would ever be).

But why then does Brad (and others) notice that using 35-PA to vertically center the image doesn't work? It is indeed the perforation height (and pitch if it is not .1870"). The intermittent pulls down biased to one edge of the perforation (not the CENTER) thus an error is set up.

Perhaps on the next review of RP-40, we should recommend that standard 35-PA and 35-IQ be made on KS-1870 perforation. If the labs need a test film based on the BH standard then it should be a separate film. 35-PA should be correct for exhibition. I have often questioned the use of BH perforations, even though, technically, 35-PA is a camera negative. It would be best to modify the camera to handle the KS-1870 perforation so it would "correct" for exhibition (now where is Stan's number).

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by John Pytlak (Member # 331) on 08-16-2000, 05:33 AM:

Steve:

SMPTE RP 40 is ambivalent on the pitch question. Section 5 says: "A perforation pitch of 0.1866 in (4.74 mm) or 0.1870 in (4.75 mm) is acceptable."

It does specify film perforated in accordance with ANSI/SMPTE 93, which is the Bell and Howell BH perf, and NOT KS.

As I noted, the 35-PA film is used by labs for lineup of (BH) pin registered printers, which would make BH-1866 the preferred perforation for that application. But I agree with you, that the bulk of the film is used for projector alignment, so it would make sense to use KS-1870 perfs. As you note, it may boil down to the ability of Stan D. to modify his camera to use KS pins and 0.1870 inch pitch film.

Let's get this on the agenda for the Projection Technology Committee meeting at ShowEast.

Posted by John Wilson (Member # 269) on 08-16-2000, 05:57 AM:

I always found that the batch we had (circa 1993/4) had the flat versions printed too high as Michael says.

But that thing is so out of date that it's really academic. Get the Sonic Landscapes. They are much more pleasing to the eye and the ear. They are also much more generic meaning you can run them with 'Elizabeth' and also run the smae version with 'Road Trip'.

...and they seem to be framed just fine.

Posted by Michael Barry (Member # 237) on 08-16-2000, 09:09 AM:

John Wilson: I suspect that obtaining a copy or two of 'Sonic Landscapes' might be the best bet. Do you think that contacting Karen would be the best way to source this?

John P and others: Thanks very much for that...I was not aware that printing heads to tails or tails to heads would cause a vertical shift (it makes sense), so I learned something there. Thanks as always!

Posted by John Wilson (Member # 269) on 08-16-2000, 05:42 PM:

Karen's not been around here of late...(at least not that I'm aware of) She will, however, take your order for your company.

Posted by Gordon McLeod (Member # 33) on 08-17-2000, 09:23 AM:

What is the concesis about the printing of the Schnieder and the THX test film. Is it also printed too high?

Posted by John Wilson (Member # 269) on 08-18-2000, 01:51 AM:

Sorry Gordon...we don't have those

can't comment.

Posted by Brad Miller (Member # 2) on 08-18-2000, 05:16 AM:

I don't have the Schneider, but will check that THX loop.

Posted by Karen Hultgren (Member # 395) on 08-23-2000, 04:09 PM:

If someone needs a replacement log film (trailer), please email me at

khultgren@dtsonline.com

Karen at DTS

Posted by Carl King (Member # 398) on 09-11-2000, 07:43 AM:

Michael

I too have noticed the DTS announcement strip has framing problems. Thanks to John's expetise I know have a possible reason. I also notice that some trailers exhibit the same problem. The opening logo for the GET CARTER trailer is the same way while the rest of the trailer seems fine.

Maybe someone in quality control at the lab fell down on the job. I wonder if it would get any better if projectionist started complaining directly instead of just to their managers. The e-mail addresses of the distributors are readily available I'm sure

Posted by John Pytlak (Member # 331) on 09-11-2000, 07:57 AM:

The 0.005 inch vertical shift that sometimes happens on a bi-directional printer is normal and not "someone falling down on the job" at the lab. A larger shift would not usually be due to anything the lab did, but rather in production (camera composition or opticals).

Posted by Brad Miller (Member # 2) on 09-11-2000, 01:32 PM:

John,

Can you give us a more practical measure for the vertical pitch? Let's say we're projecting a flat film on a 20 foot high screen. Roughly how far off would that be in inches?

Posted by John Pytlak (Member # 331) on 09-11-2000, 02:12 PM:

Brad:

SMPTE 195 specifies the image height for 1.85:1 "flat" as 0.446 inches. Projected on a 20-foot high screen, the linear magnification is (20 x 12) / 0.446 = 538.

The expected vertical shift in image position on the print due to bi-directional printing is (0.078 - 0.073) = 0.005 inches, due to the difference in perforation height between BH-1866 negative and KS-1870 print perforating.

538 x 0.005 inches = 2.7 inches vertical shift would normally be expected on your 20-foot screen between heads-to-tails and tails-to-heads contact printing.

What are you finding?

Posted by Brad Miller (Member # 2) on 09-11-2000, 03:17 PM:

Worse than that sometimes from reel to reel.
On registration, it is insane. I'll have to go down with a measuring tape and get you some numbers to play with. Bring It On was a print with pathetic registration.

Posted by John Walsh (Member # 168) on 09-11-2000, 07:07 PM:

I know this has nothing to do with what JP and Brad are talking about, but if you frame up "Bring It On" just a little during the scene where Kirsten Dunst is dreaming she has no top on, you will have a lesson on why it is important to frame correctly.

Posted by John Wilson (Member # 269) on 09-15-2000, 02:48 AM:

I would have thought that would be a very good reason to frame incorrectly

Unless of course you're telling us she really has clothes on! (please let the latter be untrue!)

Posted by John Walsh (Member # 168) on 09-15-2000, 11:03 PM:

Why, Mr. Wilson, this is a professional motion picture news group.

Which means; maintain a professional decorum as you pass that Jagermeister and move that framing knob.....