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Topic: The "Physics" of Motion Picture Projection.

Will Kutler
Phenomenal Film Handler

Posts: 1506
From: Tucson, AZ, USA
Registered: Feb 2001

posted 11-10-2004 06:36 PM

One of my current college courses is Physics 112 (Basic Physics II). I would highly recommend this class to those of you who want to get a little better understanding of what makes projection equipment work. This is a generall education class offered at just about any community college or university.

Topics include basic electricity, magnetism, light, reflection (mirrors), lenses, etc.

However, this class does not delve deep into practical topics such as VOM/Multi-Meter usage, electrical component idetification, soldering, etc. A basic electronics course will cover these topics.

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Manny Knowles
"What are these things and WHY are they BLUE???"

Posts: 4247
From: Bloomington, IN, USA
Registered: Feb 2002

posted 11-11-2004 01:18 AM

I'll be right over. [Roll Eyes]

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

posted 11-11-2004 06:57 AM

Well isn't that just cute. You can go to panty raids together.

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Will Kutler
Phenomenal Film Handler

Posts: 1506
From: Tucson, AZ, USA
Registered: Feb 2001

posted 11-11-2004 03:14 PM

I think Manny needs to reread my origonal post. Physics 111 and 112 are the two basic "general ed" physics courses offered at all jr. colleges and universities. Just like freshman English, College Algebra, Trig. Calc., etc.

You can also find references and general help tutorials to these classes on the internet. One good source is WWW.PHYSICSCLASSROOM.COM (but I think this mostly deals with Physics 111).

And to further clarify myself, Physics 112 will help you understand how and why components like resistors and capicators work, the principles of Voltage, Amperage, Resistance and Wattage. How to calculate values in series, parallel and compound circuits. The principles of electromagnetism. What light is, different spectrums, how light bends, why and how mirrors and lenses work, etc.

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Daniel Alt
Expert Film Handler

Posts: 111
From: Lakewood, OH, USA
Registered: Mar 2004

posted 11-11-2004 03:40 PM

I have a M.S. in astrophysics from Yale. (No kidding) It has not helped me one little bit in keeping the fershluggener projectors working. Which is not to say physics isn't cool. Just that the theory isn't always relevant to the practice.

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Dominic Case
Expert Film Handler

Posts: 131
From: Sydney NSW Australia
Registered: Aug 2003

posted 11-11-2004 07:38 PM

quote: Daniel Alt
I have a M.S. in astrophysics from Yale. (No kidding) It has not helped me one little bit in keeping the fershluggener projectors working.

I bet it has. Not in terms of what you know about the origins of the universe or relativity or black holes, but in terms of the discipline of logical thinking, analysis of problems etc.

quote: Daniel Alt
Just that the theory isn't always relevant to the practice.

Ah! The difference between theory and practice is that in theory there is no difference, whereas in practice there is a difference.

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

posted 11-12-2004 12:18 AM

Or you can think of the business as a black hole that has sucked in many fine people who might otherwise have led productive lives, me included! [evil]

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Edward Jurich
Master Film Handler

Posts: 305
From: Las Vegas USA
Registered: Jul 2003

posted 11-12-2004 09:12 AM

I have a constant tit-for-tat with an old friend about film vs digital projection. His last email quoted some info on how everything including the universe is digital, a matter of matter if you will. So I reply that then, motion picture film is digital and actually more stable than DLP. No reply from him yet.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 11-12-2004 12:44 PM

Each silver halide grain in a film is either exposed or unexposed (1 or 0 state). So at the molecular level, film IS digital, and has been for over a century! [Cool]

Film's great latitude comes from having millions of grains, with a wide variety of sizes (sensitivities), producing a tone scale well beyond that of typical digital systems [thumbsup]

. The random distribution of grains also avoids aliasing artifacts [Smile]

, unlike the fixed pattern of pixels in digital imaging systems. [dlp]

So, Kodak has been a leader in Digital Cinema right from the start! [Big Grin]

http://www.kodak.com/go/dcinema

quote:
ORLANDO, FLORIDA, (October 22, 2004) - Eastman Kodak Company announced today at the annual ShowEast Conference that the company is taking a major step forward in its goal of making high-quality digital cinema available for motion picture exhibitors around the world. The company is demonstrating the Kodak Digital Cinema Solution for Feature Presentations, a bundled package of hardware, software, and support services.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 11-12-2004 01:54 PM

quote: John Pytlak
Each silver halide grain in a film is either exposed or unexposed (1 or 0 state).

But John,
Doesn't the intensity of the light at any certain grain actually determine how dense that actual grain is.....? So in effect you may actually have a range of 0.0 to 1.0 per grain which is how digital really should be but can't.

Mark

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 11-12-2004 01:59 PM

Not really. Once the grain is hit by photons, it will develop. The way you get a range of tones is to have a variety of grain sizes that vary in sensitivity to light, either blended or in separate emulsion layers. If all the grains are exactly the same size and sensitivity, you get a very high contrast, low latitude film. A "lith" film is the most extreme example --- all or nothing, black or white, 1 or 0.

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

posted 11-12-2004 03:54 PM

Perhaps you can explain why development must be limited and cannot just run to completion. If you do then all grains are developed whether exposed or not. So how does time (and temperature and concentration of developer) affect the process and the resulting gamma?

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 11-12-2004 04:13 PM

quote: Steve Kraus
Perhaps you can explain why development must be limited and cannot just run to completion.

Its not something that is really a limited time thing. All film should be fully developed to completion to yield proper contrast range and gamma curves if exposed normally based in its ASA rating. Sure, you can leave film in for shorter or longer time periods but if left in the soup for a shorter period you will get a thinner negative(or darker for positive process).... left in longer it will over develope and get either darker(or lighter for positive process). Film which is pushed in speed is effectively under-exposed and then over-deveolped to yield a "normal contrast image". There is a point at which all halides are fully developed and this is normally the specified time at a given temperature for the developer/film combination you are using....

But John can probably explain this better......

Mark

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

posted 11-12-2004 07:10 PM

What I meant by completion is that if you leave it in indefinitely you'll get back a solid black negative. If only light-activated grains were converted to silver that wouldn't happen.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 11-13-2004 08:39 AM

Here is what developed silver grains look like:

Notice the developed silver grains vary in size, but are generally all black (not shades of gray).

It may take more than one photon to produce a latent image, but once the silver halide grain has a latent image, it will develop into silver. If you overdevelop the film, even some grains without a latent image will develop into silver, usually the larger (faster) grains first. This caused "fog", or an increase in the minimum density of the image. Eventually, all the silver halide will be turned to silver by the developer.

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