Understanding photometric data at DVinfo.net

Allen Brodsky · January 19th, 2004, 11:44 AM

I'd like some help in interpreting photometric data for different brands of fresnels (at the same wattage and same bulb), specifically, the data in the B&H Lighting Sourcebook.
For the spotlight position, for example, it would seem to me that a light that projects a narrower beam with more footcandles (finer and brighter) is preferable to a light with a larger beam and/or less footcandles. Or, is this more a matter of preference or what best suits lighting a given scene?
When does the difference between footcandles become significant? When they differ by 10 (180 vs 190), or 20, for example?
In general, is photometric data a useful factor in comparing quality of different brands?

Ken Tanaka · January 19th, 2004, 10:28 PM

Hello Allen,
Specific photometric data is less important for videography than it might be for shooting on film. Since video is much more adjustable to lighting conditions than film specific "x footcandles at y feet" data are generally not guiding selection criteria.

The key factors when selecting lighting concern the characteristics of the light you need to provide. That is, you select your instruments much as a surgeon might select instruments; for the job at-hand. For example, diffused tungsten or flourescent intruments for soft light, fresnels or open-faced instruments for harder direct light. Wattage and lamping options within an intrument genre tend to be primary considerations for videography.

As you progress with your work you'll probably want to build a lighting kit that can adapt to nearly any requirement.

John Jackman's "Lighting for Digital Video & Television" is an excellent affordable primer on the subject.

Allen Brodsky · January 21st, 2004, 08:12 AM

Ken,
Thanks for your response. I've read the Jackman book and agree that it's a good one.

January 19th, 2004, 11:44 AM	#1
Allen Brodsky Regular Crew Join Date: Jun 2003 Location: Eatontown, NJ Posts: 118	Understanding photometric data I'd like some help in interpreting photometric data for different brands of fresnels (at the same wattage and same bulb), specifically, the data in the B&H Lighting Sourcebook. For the spotlight position, for example, it would seem to me that a light that projects a narrower beam with more footcandles (finer and brighter) is preferable to a light with a larger beam and/or less footcandles. Or, is this more a matter of preference or what best suits lighting a given scene? When does the difference between footcandles become significant? When they differ by 10 (180 vs 190), or 20, for example? In general, is photometric data a useful factor in comparing quality of different brands?

January 19th, 2004, 10:28 PM	#2
Ken Tanaka Retired DV Info Net Almunus Join Date: Dec 2001 Location: Chicago, IL Posts: 6,943	Hello Allen, Specific photometric data is less important for videography than it might be for shooting on film. Since video is much more adjustable to lighting conditions than film specific "x footcandles at y feet" data are generally not guiding selection criteria. The key factors when selecting lighting concern the characteristics of the light you need to provide. That is, you select your instruments much as a surgeon might select instruments; for the job at-hand. For example, diffused tungsten or flourescent intruments for soft light, fresnels or open-faced instruments for harder direct light. Wattage and lamping options within an intrument genre tend to be primary considerations for videography. As you progress with your work you'll probably want to build a lighting kit that can adapt to nearly any requirement. John Jackman's "Lighting for Digital Video & Television" is an excellent affordable primer on the subject. __________________ Lady X Films: A lady with a boring wardrobe...and a global mission. Hey, you don't have enough stuff! Buy with confidence from our sponsors. Hand-picked as the best in the business...Really! See some of my work one frame at a time: www.KenTanaka.com

January 21st, 2004, 08:12 AM	#3
Allen Brodsky Regular Crew Join Date: Jun 2003 Location: Eatontown, NJ Posts: 118	Ken, Thanks for your response. I've read the Jackman book and agree that it's a good one.