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This topic comprises 4 pages: 1 2 3 4
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Author
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Topic: SRD - Penthouse or Basement - preference?
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 04-17-2005 12:58 AM
In general, you should align the analog first. With CE...always analog first. The lateral adjustment of the solar cell is quite limited thus you want the film to be fixed to the analog cell. With CE you then bring the LED into alignment with that. After that is said and done...the digital can then be brought into alignment with what you have already done...again, with CE the LED can be precisely matched to what you have done in the analog alignment so both are exactly where they need to be. The CE digital reader allows for easy lateral adjustment to have it dead center. What you don't have with the CE reader is the ability to move either reader vertically BUT they reference their readers off the sound drum and then pin everything so that alignment remains true. It is rather easy and fast to bring a CE system into precise alignment.
On the Kelmar system...for Century there is way too much demolition that is needed but good results can be had. I've done several JJs with the Kelmar (they are the only ones that properly support the R-50 soundhead for 70mm to bypass through the head).
Kelmar's problem is that their LEDs do not adjust and that they have too many variables. The LED bracket is not referenced to anything and is limited to just the mounting screws. Likewise, there is nothing really referenced on the analog reader...just limited by the mounting screws. As such, you can have the LEDs skewed to the reader pick up and hence some back-and-forth alignment may be needed to get it all precise. Since laterally you are most restricted on the analog side...you really should start there but since you pretty much have to remove the analog reader to fully adjust the digital one...you kinda have to finish with the analog reader.
Century is much more of a pain system in either case...their machining has generally sucked throughout the years. You almost need the CE 30-series to properly align the older Centuries (and some of the later ones too). The film should not skew as it goes from sprocket, to drum to sprocket...as such you may need to adjust the reverse reader cell to get it to laterally center up on the film...likewise the LED may need to be shimmed (on a Kelmar) to get it to line up. I have not come across this on any Simplex but several Centurys.
Another variable in the analog alignment is how the various companies have dealt with reflections in their lens tubes....Kelmar silk screens their cells while CE hand paints them (on the outer part of the slit)...sometimes the silk screen isn't well aligned. With the analog cell you really are aiming for a bullseye. The center must be center and the edges of the modulations should not be clipped. With digital, you have a CCD that is wider than the image...you have some slop factor. This is another reason I get analog precisely aligned first, then bring digital into conformity. Note too, on the CE readers, it is pretty easy to adjust magnification on both the digital and analog readers and sometimes you are best served by checking those...too little magnification on the analog will have your cell picking up the edges of the track and finding time code or other noises.
However, regardless of which system, digital or analog, one should get their soundhead mechanically right...it all starts there.
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Mark Gulbrandsen
Resident Trollmaster
Posts: 16657
From: Music City
Registered: Jun 99
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posted 04-17-2005 09:28 AM
quote: Steve Guttag
I'll put my basements up against your penthouses...they will track any film your penthouses will.
Steve,
The main problem I have with basement stuff is that installing it in the optical soundhead will yield more inconsistent results overall because the optical soundhead itself is more likely to need regular attention to keep the digital working at its best, particuluarly 5 star and SH1000 type. Century is less maintainance generally, but the projector heads more than make up for that. As I mentioned there is a place in the buisness for basement type stuff but its not a really good thing for theatres that do not get "normal maintainance" on a regular basis or decent prints. About half the 400 or so screens we service get what I would call normal maintainance so I think you can see why I feel the way I do. In my experience even twice yearly is not enough tweeking for reliable operation of the older basement stuff. Sure they all work but there are far more critical variables having it down there. Penthouses for the most part stay working with little to no maintainance while optical soundheads don't stay working properly with out some occasionnal maintainance. Although I think you'd find yourself in a minority I'm glad that yours work out so well, but out here they just don't while the penthouses always keep on chugging along. The fact is that there are less variables that can be affected by lack of service on penthouses in general. There is alot of dust problem out west that you don't have back east and that is another contributing factor towards unreliable basement results for the most part. Many theatres here, even first run, have trouble getting decent SRD tracks on brand new prints let alone on second run and indeed many second run theatres get prints that have damage that even penthouse readers have a hard time with let alone a basement... even your basement readers would not read them and many times there are no extra prints to get. So perhaps you can understand whay we've stuck with what works reliably for us out here.
Louis,
Out of round gear..... now why don't you replace them dude? They can and will run really nice. Actually I've measured pretty low W&F specs on SH-1000s in the past. They generally average around .1 to .15% which is pretty decent and as good as many 35mm mag dubbers. Those out of round gears will certainly affect analog playback!! The Century direct drive JJ always measured higher than the 35mm Centurys, with the movement pulled it measured as good. I never saw much W&F difference between standard or direct drive except when a Bodine sync motor was used on DD, then it was consistantly higher because of hunting between poles. Three phase electronic drive always measured the lowest when set up on any Century. Also, the use of ABEC 7 bearings in any SH-100 type or Century sound head helps tremendously on the W&F specs!! The lowest W&F I ever measured on an optical repeoducer was on the Kalee 21 projector at .07% which is about the residual in the SMPTE film.
Mark
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