Film-Tech Forum ARCHIVE: Shedding Light on Darkroom Illumination

This is topic Shedding Light on Darkroom Illumination in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by John Pytlak (Member # 331) on 10-21-2002, 08:56 PM:

Here's an SMPTE Presentation about Darkroom Lighting that I did several years ago. Some of the principles may apply to lighting theatres (aisle lights and dimly lit projection rooms):
here

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: here

Posted by Scott Norwood (Member # 30) on 10-22-2002, 08:58 AM:

I've seen both the LED arrays and sodium lights used in darkrooms used for B&W work. My personal preference was for the LED arrays, as they seemed brighter and easier on the eyes, but both seemed to work well.

Since most aisle lights (the ones that mount on the sides of theatre seats) are incandescent, has anyone switched to red bulbs or used red gels for these? I've never seen this, but it seems like it would be worth trying.

Posted by John Pytlak (Member # 331) on 10-22-2002, 09:17 AM:

As noted in the paper, for general illumination of darkrooms when using color print films or paper, the very narrow spectral output of low pressure sodium vapor lamps is ideally suited, as 589nm is a point of lowest sensitivity for the film/paper. An amber LED peaks near 590nm, but has a fairly broad gaussian-shaped spectral output, so the "safe time" will be less before fogging occurs.

Accidental overexposure of print film to these sodium vapor/amber LED/Series 8 "safelights" is the usual source of any cyan or blue colored fogging on prints (typically near lab splices, where the operator needed extra light/time to make the splice). The principles outlined in the Kodak paper were intended to help labs minimize this type of exposure and fogging.

At ShowEast, several vendors were showing LED illumination for lighting aisles and stairs in theatres, both as "path lights" and as flooded illumination.

Posted by Jeffry L. Johnson (Member # 453) on 10-23-2002, 12:26 PM:

I am not claiming that theater patrons have fully dark-adapted (scotopic) vision. But it does take several moments for vision to adjust to subdued lighting in a theater auditorium. So, wouldn't red light be better in theaters since it does not affect dark-adapted vision?

Posted by John Pytlak (Member # 331) on 10-23-2002, 01:02 PM:

Red would be the best choice to maintain dark adaptation. So red lights in dark hallways or other waiting areas would let people "keep their dark eyes".

For path lighting, green LEDs can be run at the lowest light level, since the eye's sensitivity peaks in the green. But red LEDs are often used to denote "danger" or "stop".

You are correct that the 16 footlambert screen luminance falls in the range of "mesopic" vision --- brighter than scotopic "night vision" using the rods, and not fully having the color and acuity of photopic vision using the cones. Pictures appear to have better color and sharpness as the light level increases:
here

Posted by Chris Erwin (Member # 176) on 10-23-2002, 07:01 PM:

We've come a long way in lighting darkrooms since I first started with a bare red bulb as a safelight!

--Chris