Film-Tech Forum ARCHIVE: 7000 Watt Lamphouse for DI, good idea?

my profile | my password | search | faq & rules | forum home

»	Film-Tech Forum ARCHIVE » Operations » Film Handlers' Forum » 7000 Watt Lamphouse for DI, good idea? (Page 3)

This topic comprises 6 pages: 1 2 3 4 5 6

Author

Topic: 7000 Watt Lamphouse for DI, good idea?

Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 01-17-2005 08:32 PM

If memory serves didn't kollmorgen or Hilux used to make a extremely fast long focal length lens in the 4" diameter that was f 1.7

| IP: Logged

Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 01-17-2005 10:05 PM

Yes, we have boxes of 4" diameter Kollmorgen and B&L's in the CLACO "Retired Equipment Dungeon". And there are definately 4 inchers in there.

Our last In Town Drive In uses a special 9.5" Kollmorgen for its flat aspect ratio.

Mark @ CLACO

| IP: Logged

Justin West
Master Film Handler

Posts: 271
From: Peoria, IL, USA
Registered: Jul 2001

posted 01-17-2005 11:06 PM

Hmmm, well that Super-Cinefor sounds interesting...but the lens opening on the Century C I have is smaller than 4" diam. Is there an adapter to accomodate this model lens and, if so, is it advisable to use? [Confused]

| IP: Logged

Tim Reed
Better Projection Pays

Posts: 5246
From: Northampton, PA
Registered: Sep 1999

posted 01-18-2005 01:57 AM

quote: Steve Guttag
knowing the physics of the lens should help in choosing the most suitable one.

That, and knowing what's available. But it doesn't entail splitting hairs over the manufacturer's rating. C'mon, now. You can only go by what's on the barrel. [Roll Eyes]

If 4" B&L's are available, and if they have not yellowed as their red-ringed (and now, some silver-ringed) anamorphic mates have, then that certainly would be a good choice under the circumstances -- although I have not seen any of those around for several years, at least not in good condition. But good suggestions for sources. Thanks all.

That's right, Gordon, I believe it was Kollmorgen.

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 01-18-2005 10:34 AM

quote: Tim Reed
That, and knowing what's available. But it doesn't entail splitting hairs over the manufacturer's rating. C'mon, now. You can only go by what's on the barrel.

That is poor advice. Manufacturer's tend to stretch the truth in their ratings and to just go by what is on the barrel will yield you, in the case of lenses, wrong focal lengths (since they rarely fall exactly on the mm) and when considering light, the "f" number is important.

Justin...if you have a small lens mount "C" then the Schneider 170mm is your best bet. You can't adapt your projector for the large lens.

Steve

To put into modern terms...if you believe the lumen rating of video projectors, you will invaribly put in one that is too dim. Or even better, believe the contrast ratios that vidiots quote...I defy anyone to measure it and come up with their number...it would be like taking a film projector and capping the lens, with the douser closed and comparing to open gate in a perfectly blackend theatre...it isn't reality.

Don't take me wrong on this, I can understand that if it says f/2.4 you are going to take it at face value...but when considering light, it would be better to recognize that the physics of optics is suggesting that either the lens is not 170mm or it is not indeed f/2.4. You are welcomed to ignore me too.

Steve

| IP: Logged

Andrew McCrea
Jedi Master Film Handler

Posts: 645
From: Winnipeg, Manitoba, Canada
Registered: Nov 2000

posted 01-18-2005 12:54 PM

If you read the parts manual, there should be lens reducers available.

I really like this new lens calculator- my only problem is that I got 30mm for flat and 61mm for scope in my experiment. I went to the ULTRA-STAR HD PLUS and BLUE-STAR HD literature. For scope, they have 42mm, 45mm and 48mm. For flat, they do have 30mm. Do they manufacture adpaters to make scope lenses larger?

Any tips. For a Schneider scope lens and flat lens, what would I be looking at? One Super Cinelux and one Cinelux Premiere?

Thanks.

| IP: Logged

Aaron Sisemore
Flaming Ribs beat Reeses Peanut Butter Cups any day!

Posts: 3061
From: Rockwall TX USA
Registered: Sep 1999

posted 01-18-2005 11:15 PM

Andrew, you would use a 60mm (nearest size up from your computed 61mm) Isco HD Plus (red) prime lens with the anamorphic adapter of your choice. Or you can use the 60mm HD Plus (red) integrated anamorphic lens (prime and anamorph in a compact single unit).

No, you cannot make a scope lens larger with an adapter (to use a Magnacom with an anamorphic would cause many problems with vignetting and such)

There is no Blue-Star integrated available in 60mm, so you would have to use a Blue-Star anamorphic attachment with the 60mm prime of your choice.

If you wanted to go Schneider, just get the same lens sizes and apropos anamoprhic attachments.

That's how it works.

-Aaron

| IP: Logged

Tim Reed
Better Projection Pays

Posts: 5246
From: Northampton, PA
Registered: Sep 1999

posted 01-22-2005 06:00 PM

quote: Steve Guttag
Manufacturer's tend to stretch the truth in their ratings and to just go by what is on the barrel will yield you, in the case of lenses, wrong focal lengths

Nothing can prevent you from getting a lens that has the wrong focal length on the barrel! That's the manufacturer's problem, not yours. This has no bearing whatsoever on making recommendations for a lens compliment.

quote: Steve Guttag
Justin...if you have a small lens mount "C" then the Schneider 170mm is your best bet.

Ummm...he had that info already. Obsessing over a tenth of an f-stop didn't change things one iota.

quote: Steve Guttag
when considering light, the "f" number is important.

No kidding, Sherlock. [Roll Eyes]

You're not telling me anything I haven't known since you were in high school. [Wink]

Obviously, you want the fastest you can get for a drive-in, but if they ain't got a fast one, heh-heh... they ain't got it! Saying, "Oh, it's really more like f/2.4" might make you feel smart, but it changes nothing.

quote: Steve Guttag
it would be better to recognize that the physics of optics is suggesting that either the lens is not 170mm or it is not indeed f/2.4.

Why? No one's designing lenses here, so it doesn't matter. Understanding the relationship, yes, but not nitpicking over what's printed on the barrel. That's just silly. Besides, if there's very much of a deviation, you won't know it until you put it on the screen, anyway.

Most of us know a particular len's "mileage may vary" from what's stamped into the barrel, but it means nothing in practice because you CAN'T DO ANYTHING ABOUT IT.

quote: Steve Guttag
You are welcomed to ignore me too.

You take yourself too seriously.

| IP: Logged

Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 01-22-2005 06:57 PM

and remember the f number of a lens is only as important as the f number of the lamphouse system it is mated too

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 01-23-2005 12:50 AM

My, my....look who just got his panties in a wad.

quote: Tim Reed
Nothing can prevent you from getting a lens that has the wrong focal length on the barrel! That's the manufacturer's problem, not yours. This has no bearing whatsoever on making recommendations for a lens compliment.

I don't tend to guess at the outcome of a projection systems I set up. I want to know the focal length of the lens as well as the speed prior to chaulking it up, perhaps that isn't your way. That is your perogative.

quote: Tim Reed
Ummm...he had that info already. Obsessing over a tenth of an f-stop didn't change things one iota.

I may have missed it but he didn't specify that he had a SMALL lens mount "C" (and they came in both large and small lens mounts). As far as the f-stop...who knows what it really is but sizing the lamp and predicting the illumination would be determined on knowing the true focal length and actual f-stop. (I know, you know this already, does Justin?).

Moderator(s)...are these threads not supposed to be educational as well as just stating "use this"?

quote: Tim Reed
No kidding, Sherlock. You're not telling me anything I haven't known since you were in high school.

I'm not trying to tell YOU anything. Don't worry. You have it all figured out.

quote: Tim Reed
Obviously, you want the fastest you can get for a drive-in, but if they ain't got a fast one, heh-heh... they ain't got it! Saying, "Oh, it's really more like f/2.4" might make you feel smart, but it changes nothing.

First, I don't have to "feel smart". Again...going back to the larger lenses...that probably can be obtained by a bit of looking...but one of the machines is a small lens mount so that was ruled out...just recently. And again, you might not care what you are working with before you chaulk it up, I do.

quote: Tim Reed
Why? No one's designing lenses here, so it doesn't matter.

Again, I feel one should know what they are working with. And if I was just trying to spout off knowlege...I could have gone into lens design equations and such...now that would be be superfelous for this discussion. However in this situation, noting that something does not compute would lead me (and some others, clearly not you) to wonder what the actual focal length is to ensure it is properly sized and how much light will actually be needed.

quote: Tim Reed
Most of us know a particular len's "mileage may vary" from what's stamped

YOU might know that, particularly with Schneider Lenses but I doubt "Most" is an accurate statement.

quote: Tim Reed
You take yourself too seriously.

Nah, more like different methodologies. Perhaps in the future I should just heed my own advice with regards to your posts.

| IP: Logged

Richard Greco
Phenomenal Film Handler

Posts: 1180
From: Plant City, FL
Registered: Nov 2003

posted 01-23-2005 02:07 AM

You know, ya'll lost me as soon as you started with the "f" numbers

| IP: Logged

Monte L Fullmer
Film God

Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004

posted 01-23-2005 02:46 AM

quote: Richard Greco
ya'll lost me as soon as you started with the "f" numbers

..take a grab at this site, which is "f"-stop 101:

http://www.uscoles.com/fstop.htm

| IP: Logged

Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 01-23-2005 08:48 AM

quote: Tim Reed
Most of us know a particular len's "mileage may vary" from what's stamped

quote: Steve Guttag
when considering light, the "f" number is important.

And now to throw the monkey wrench into all your panties!

Sorry Steve but the F-Number of a lens is pretty much meaningless and I will side with Tim on this one. Having some film background experience, mainly on my own, I have always wondered why projection lenses are also not calibrated in T-Stops the same way professional film camera lenses are. T-Stops are much more meaningful than F-stops because F-Stops are calculated based on the geometrical limitations of the lens and this assumes the lens is perfect which no lens is nor even comes close to. This purely geometrical calculation does not take into account the loss of light in either the glass or the coatings, nor light delay thorugh the lens.... and there are definate losses in ALL lenses.

For those that are not aware, calculating the F Speed of a lens is done as follows.......

FL / PA = F Number of lens

For instance of you have a 70mm Focal Length lens with a 32mm Physical Aperature then its 70 / 32 = F 2.1875 or simply round that to F-2.2.

The T-number or the actual amount of light a projection lens passes would be determined purely photometrically, not by a geometric calculation as is done today with our supposed "Professional" projection lenses. Really they are not calibrated in a very professional manner are they and we don't have a clue as to how much light a given Schneider or ISCO lens is actually passing do we?

Hence......

The T-Stop if calculated based on actual lens photometrics is much more meaningful than any F-Stop calculation. This can also apply to reflectors.

The F-number of a Perfect Projection Lens that gives the same Image Illuminance as the Actual Projection Lens at its Physical Aperture. To take an example, if the above F-2.2 lens only transmitted 75% of the light that a perfect version of the same lens would transmit it might have a T-number of 3.2, a loss of one stop over that perfect lens! Keep in mind that the T-number presented here is only hypothetical, remember it has to be calculated photometrically as there is no simple geometric based formula!! In reality though we are getting efficiencies that are probably in the high 80 to high 90% range.

Hence I've always wondered why the so called "Professional" lenses we use on a daily basis are not calibrated more accurately..... so we know exactly what an optical system is doing. We really have no clue if we base our systems on the F-Stop. It would be easier to properly select an accurately T-Stop calibrated lens and reflector to get that last lumen of light out to the big screen. An extra half a T-Stop in a lens or reflector might get you that extra Foot Lambert or two on the screen that you'd like to be getting.

Mark

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 01-23-2005 10:35 AM

Mark,

I'll give you the whole T-Stop thing...it is indeed more relevent to knowing what you are working with....why don't lens manufacturers give it?...I would say it is based on tradition (like measuring TVs on the diagonal of an un masked CRT) and that if one were to get the true transmission on a lens by lens basis it could muck up sales a bit...that is I used Brand A for the 85mm but brand B for the 90mm since it is some fractionally better light.

We have also read right here that that to some (to paraphrase) "it is what it is" so who cares what it really is...thus all of that information is not used.

However, I would not entirely discount the whole f-stop thing as an indicator to light transmission. It is like the STC indicator to sound transmission...never mind that STC doesn't measure frequencies below 250Hz or so thus a measurable high STC might allow subwoofer signals to pass right on through that wall but it is a good indicator of relative transmission on a given wall design.

Lastly, back on topic...the whole freakin thing about the 170mm lens in this thread (I just scrolled back) was to be used in a Simplex XL. To quote:

quote: Justin West
1) Scope: 4 1/2" backup with reverse anamorphic attachment (9" with normal scope)
or f2.0, 115mm backup

2) Scope: 5" backup with reverse anamorphic attachment (10" with normal scope)
or f2.0, 125mm backup

3) Flat f2.0 170mm or 6 1/2"

4) Flat f2.3 150mm or 5 3/4"

I plan to use lenses 2 and 3 on an XL and 1 and 4 on a Century C

Lens 3 was to be used on a Simplex XL...I therefore stand with going with an older 4" diameter lens, like the Super Cinefor, it will be brighter without any real image quality penalty.

Steve

| IP: Logged

Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 01-23-2005 10:46 AM

I agree Steve. He will get a bit lower contrast ratio with that 4" lens but in a drive in situation that may be an advantage and give more apparent brightness which in that situation is a good idea. And yes the 4" will in theory give more light overall just because of its geometric size assuming the glass and coatings are at least close to todays stuff. The downside with the 4 inchers are the cememted element groups.

Mark

| IP: Logged

All times are Central (GMT -6:00)

This topic comprises 6 pages: 1 2 3 4 5 6

Printer-friendly view of this topic

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.