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Topic: Shedding Light on Darkroom Illumination
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 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. ------------------
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
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 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 ------------------
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: http://www.kodak.com/go/motion
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