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Author Topic: SMPTE Survey on Light Measurements Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-15-2013 03:30 PM                     Hello The SMPTE Study Group – TC-20F SG On-screen Light Measurement is studying the current practices for setting up and measuring the luminance of a cinema screen, and we are soliciting input from practitioners. We have prepared a short survey to gather this input. I would encourage your participation, especially if; 1. You are involved in cinema projection setup 2. You are involved in projection setup in other applications related to motion picture production Please pass this link to others who are involved with projection setup. http://survey.constantcontact.com/survey/a07e7ns6iikhhuxcsly/start We are on an accelerated schedule to complete our study report, so we are requesting your response by June 30. Please participate – this is your chance to be heard! Cordially, Matt Cowan — Chair SMTPE Study Group – TC-20F SG On-screen Light Measurement PS — Really, please. Pass this link to others who are involved with projection setup...and soon. <http://survey.constantcontact.com/survey/a07e7ns6iikhhuxcsly/start>; http://survey.constantcontact.com/survey/a07e7ns6iikhhuxcsly/start  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 06-15-2013 06:13 PM                     I think there is a mistake when it asks what test patterns are used, there are two questions both saying 2D. Also, the entire survey is a little confusing, if you're an installer some questions do not apply  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-15-2013 06:23 PM                     Yes, question 25 should probably read 'For 3D Setup: ...' - Carsten  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 06-15-2013 06:25 PM                     This survey seems to make the following assumptions: 1. Everyone is a multiplex -- they ask for info on the smallest and largest houses. What to do? Answer the same for both? Leave one blank? Make something up? 2. Film is dead -- the brand name projectors are all digital. Kinoton is absent from the list. 3. It's unclear what we're supposed to do if we have several projectors aimed at one screen. Also, note that they don't permit you revisit answers on previous pages. I got an error when I tried to page backward. And paging backward twice (double-click) seemed to skip FORWARD. For initial setup, I always followed RP-98. It calls for 54 measurements (9 areas of the screen, each from 6 seats) per format, per projector. I made an Excel spreadsheet that helps with this. For periodic checking, I simply measure the center of the screen from the seat that has my name on it.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-15-2013 07:30 PM                     I just finished it, and left out second/small screen. - Carsten  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-16-2013 09:22 AM                     I have already brought the question typos to the appropriate people. In particular, questions 8, 15, 22, 24/25. Use comments for anything that does not seem to apply or is confusing. The survey was designed to be as general as possible and not target multiplexes so if you are a single screen, then omit either the large or small theatre and only fill one out. The goal is to find out HOW people are PRESENTLY measuring their light, not guide anyone into a particular method. This survey does concern Digital Cinema and not Film so much though most of the questions would apply to both. It probably would have been better if "Digital Cinema" had been used in its name/request for participants. I gave it a try too and I WAS able to go back. So I guess it is browser dependent (I used Opera on both my mobile phone and Mac. I didn't save my results since I was merely testing the survey). It would be nice to see your spreadsheet, Manny. It is nice to know that someone follows RP98. Do you also follow S196?  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 06-16-2013 12:10 PM                     So Manny can you tell me how do you find customers happy to pay for your time when you're doing light measurements 54 times?  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 06-16-2013 01:11 PM                        It'd be interesting to see Manny's spreadsheet from several auditoriums. How much does the measured luminance vary with the measured area of the screen? How much does it vary with measurement (seat) position? How does it vary auditorium to auditorium? Of course one way to get the 9 measurements at once would be to use a USL PSA. Manny, any chance at seeing your measured data? I did a bunch of research into SMPTE Journal articles for the SMPTE group that is working on this. Here are a few interesting things I found: 1. With the change from carbon arc to xenon lamps, screens that measured the same looked different. This is apparently due to the spectral response of meters (and the standard) not precisely matching that of the eye. Part of this is that we are viewing the screen in a dark auditorium. In addition, we are using a fairly old standard (1931) for the spectral response of the meter. I don't recall what the difference was, but I think it was substantially below the approximately 20% tolerance in specified luminance for theater screens. 2. Bigger screens look brighter with the same measured luminance. One article proposes a "derating" or decrease of specified luminance as screen size increases. 3. In 1951, there was a proposal to deal with luminance "fall off" as you move from the center of the screen. The proposal was to vary the number of perforations per unit area (more perforations per unit area in the center of the screen to reduce luminance at the center of the screen). Harold  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 06-16-2013 09:21 PM                        I'm with Manny in that this survey is written poorly. I do projection work for a number of different venues, running both film and various video and D-cinema formats. I have not done 3D shows anywhere. I don't have one venue for which I am responsible--I take care of a few, none of which is a full-time movie theatre, and none of which is a multiplex. How am I supposed to answer these questions? Or would my answers even be valuable to a survey that seems to be largely geared toward movie theatres.  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 06-17-2013 08:17 PM                     Steve, YES -- 196M is a Normative Reference in RP98 -- IU Cinema meets "Review Room" spec. -- You spec'ed us well -- I'll send you the spreadsheet template tomorrow when I return to work. Marco, I'm not paid by the hour. I'm paid to do it right. Also, note that I'm working at a single-screen cinema. Harold, there isn't exactly a wealth of data to be mined here. My current cinema is a single screen. So was the last one. At any rate, I'm not releasing specific luminance data from any of my employers' cinemas. I can tell you, however, that the numbers don't vary much from seat-to-seat, which is why I feel 100% comfortable doing "spot checks" from just one location.  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 06-17-2013 08:35 PM                        Manny, Thanks for the response. I understand your concern. It IS nice to know that luminance is pretty consistent throughout the auditorium. Thanks! Harold  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 06-17-2013 08:45 PM                     As you'd imagine, the screen itself is definitely a factor in the uniformity. I think we are using a SnoMatte screen with a gain of 1.0. Maybe Steve can confirm/correct this, since he spec'ed our venue (and has an excellent memory). I wish this was the sort of thing I could remember off the top of my head but, alas, it is not -- If Steve doesn't answer before I get back to work, I'll update after I've had a chance to double-check. Anyway...I don't wanna hijack the thread...or maybe this is good since it keeps bumping it up to the top..?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-17-2013 09:58 PM                     My preferred screens are the Stewart Snomatte 100 (matte white...and it really is) and the Stewart Ultramatte 130. Since you have 3D, I may have gone up to the Ultramatte130 but if you are getting that really uniform readings...then it is the Snomatte100. That screen will make a picture look better than on other screens. The Ultramatte 130 will add bit of pop to an image and it is the highest gain that will conform to SMPTE specs. Manny, I ask about S196 versus RP98 since they are different techniques. One has you divide the screen up into 9 sections (tic-tack-toe board) and measure the center of each of the 9 sections. The other has you measure 5% in from the edges/corners.  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 06-17-2013 10:17 PM                     My spreadsheet is designed around RP98 -- 9 cells arranged to represent the screen -- that is the measurement strategy I follow. Even so, it double-checks the edge values against the center value, to verify that they conform to BOTH the Standard and the RP. (Even though I may/may not be measuring exactly 5% in.) Within each cell, the name of each spec will turn green if the measured value conforms to it. My main concern with S196 is whether we meet the criteria for "Review Room" which, IIRC, RP98 does not address.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 06-18-2013 10:19 AM                     Manny - what instrument do you use? - Carsten  |  IP: Logged

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