Thanks,

Jeff Joseph
SabuCat Productions

You'll need to get a light meter that allows for the interuption of the shutter to get accurate readings. Normal light meters don't allow for this. You be able to use it to get a comparison between other screens with a know reading - that may give you an idea. Maybe some others out there may have some thoughts on this.

Maybe someone out there knows where to get on. The company I work for has had one for about nine months and it has been very usefull in identifying screens which need working on in regard to light. We have been busy installing bigger rectifiers in a few places and trialing with larger lamps in other situations.

A question that I would like an answer for is:

Is brighter always better? Can you be outputing too much light?

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Anyone else experience this?

The SMPTE specification for light levels on screen is 16 foot-lamberts (fl), +/- 2 with certain distribution characteristics, etc., etc. Unfortunately, ther have been too many theatres that are under-illuminated. We've all heard the stories about 6 & 8 fl, etc. I've seen some of them and know they are still out there.

Hollywood folks will sometimes make a compromise and films get timed for lower light levels they expect in theatres. Instead of timing for 16, maybe they time for 12fl or even less -- depends on the film's content, audience appeal, etc. That film will look okay on lower light screens -- not right, but okay. Put it in a well-lit screen, though, and it will look over-exposed, washed out, without any vibrant colors and contrast.

The other side of the book are the darker films, particularly the animated films that really need 16fl being on screen. As good as they look at 16fl, my impression is they look GREAT with 18-20fl. Colors jump off the screen, contrast is terrific and other visual details are present and really obvious to the viewer. But look at them with 10-12fl and they are dim and lifeless.

Imagine a film like Bladerunner with 10fl, and then think of it at 16 or 18fl -- totally different experience. (Then add a big screen, digital sound, junior mints and a date ... ah, movies.)

It's interesting. Correctly timed films shown with proper light levels look terrific, and higher light levels (in my experience) even improve the image quality. Thankfully, most of the more recent cinemas with all clients are working hard to provide and maintain proper light levels. In general, a presentation in a "normal" cinema usually has the potential to be what it should be on screen.

Personally, I'm not the biggest advocate of the 16fL level...more often than not, when I have a theatre set up to 16fL, the blacks turn to green or gray. If their is bright objects nearby then the blacks won't look so bad...if it is a dark scene, then it is obvious the black level is reached. EK prints can get away with brighter images, from my personal observations. Also IB Tech prints can run brighter levels since their blacks are so good.

For the typical release print though I find the minimum on a medium to small appearing screen should be 12fL. Below that, the picture starts to look dull. At 14fL the picture starts to really get some "snap" to it, the colors start to jump out at you, bright sky will make you squint. So if I were able to make the rules 14fL would be my target. What I like about 16fL is that without it theatres would strive for even lower light levels! In small review rooms 16 -22fL running EK prints can really knock your socks off...unfortunately, this is what the film makers see, it isn't realistic nor would look as good with the mass produced print.

One phenominon I have have observed is that extremely large appearing images look good with lower light levels. That is, when IMAX screens only have 8-12fL, nobody really notices that they are dimmer than the typical cinema. I'll take a 12fL picture on a 30 x 72' screen over a 16fL on a 10 x 24 screen. I'm sure that if someone were to do a study (and that study may have already been done) it would come down to the total amount of light collected by the eye rather than the light on any one point on the screen.

Steve

I think it's something to do with "perceived image size". I know when I sit in the front of the theatre where the screen is very large appearing, it appears to be brighter -- a lot brighter. I think there is a correlation of some kind and it would be interesting to know more about it.

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I've recently written quite a bit about the subject:
http://www.kodak.com/US/en/motion/newsletters/reel/spring98/pointers.shtml http://www.kodak.com/US/en/motion/newsletters/reel/december99/pytlak.shtml http://www.kodak.com/US/en/motion/newsletters/notes/march2000/pytlak.shtml http://www.kodak.com/US/en/motion/newsletters/notes/june2000/pytlak.shtml

Standard SMPTE 196M specifies "open gate" screen luminance with an aim of 16 footlamberts, and an allowed range for theatres of 12-22 footlamberts. This is so theatres reproduce what was seen and decided in the carefully controlled laboratory screening room, which in almost all cases today, is maintained at the aim of 16 footlamberts.

In general, "Brighter IS Better". But going much above the 22 footlamberts maximum allowed by the standard has three pitfalls:

1. With the most commonly used two-blade shutter (48 interruptions per second), SHUTTER FLICKER becomes more noticable at higher light levels. You can project film at much higher screen luminance without flicker IF you use a three-blade shutter (72 interruptions per second).

2. When negatives are underexposed, the maximum density (darkness) in the print is reduced, resulting in "smoky" shadows. For example, a very underexposed negative may result in a print with a maximum density of only about 2.0, meaning that 1/100 of the light gets through the "black" area. A normally exposed negative produces a print with a maximum density of 3.0, meaning that only 1/1000 of the light gets through the "black" area of the print. An overexposed or "rich" negative printed onto Kodak's new VISION Premier Print Film may achieve black densities above 4.0, meaning that only 1/10000 of the light can get through the black areas of the film frame, resulting in a very "rich" and dark black.
Excessive screen luminance may make the blacks in underexposed scenes look too "smoky", so blacks look "gray" or have a color tinge.

3. When the negative has good exposure, producing prints with "rich" blacks, projecting the prints at higher than 16 footlamberts may look very good. BUT, it may not be what the director and cinematographer want! For example, if there is a villian hiding in the dark shadows, projecting with a screen luminance that is much too high will actually allow the audience to see TOO MUCH detail, and perhaps recognize the villian when they were not supposed to! Or the brighter colors that result when screen luminance is high may be more saturated than the cinematographer intended.

So, in general, try to stay in the 12 - 22 footlambert range specified by SMPTE 196M, and ideally at 16 footlamberts.

But, if a film is shot and printed to be shown at a very high screen luminance, the results can be STUNNING! I have projected well-exposed prints with a 3-blade shutter at light levels of over 50 footlamberts, and the picture quality is AMAZING! It can be done with today's technology, but since most theatres have 2-blade shutters, and have difficulty lighting big screens, the present 16 footlambert standard is the aim you should shoot for now.

BTW, work published in "Photographic Science and Engineering" by C.J. Bartleson of Kodak in 1965, shows that optimum preceived quality of projected images is a function of screen luminance, with maximum quality achieved at 413 footlamberts for still images (Kodachrome slides).