Lumen vs. ANSI Lumen

[Kelina Kwan]

Can somebody tell me what is the relationship between lumen and ANSI lumen?
I have searched online and other encyclopedias, and the ANSI site but I
couldn't find anything on ANSI lumen. How many ANSI lumen is equivalent to 1
lumen?

Thanks.

Kelina

[Georg Mischler]

The definition of ANSI lumens was created to take the quality
of the light distribution into account for image projectors,
while the "normal" lumen just defines the total amount of
luminous flux emitted.

From http://www.philipslcd.com/faq633tx.htm:

: Difference between different light output measures Lux,
: Lumen, Ansi Lumen?
:
: Following the explanation on light output definitions.
:
: Lumen = Amount of light coming out from the projector lens.
: Lux = Illuminance (refers to light falling on a surface);
: Lux = Lumen/m2
:
: A so called 100 Lumen projector, creates 200 lux on a 40" screen
: (« m2) or 800 Lux on a 20" screen. The American National
: Standardization Institute (ANSI) has issued a more accurate
: brightness measurement method: The ANSI 9-points measurement.
: It gives a good indication of the average brightness of the image
: taken the brightness uniformity into account. Projectors with
: a "Hot-Spot" will have a high Lumen figure with a relatively
: low ANSI Lumen figure. For our projectors with almost no "Hot-Spot"
: the ANSI Lumen and Lumen are almost equal.

Have fun!

-schorsch

--
Georg Mischler -- simulation developper -- schorsch at schorsch.com
+schorsch.com+ -- lighting design tools -- http://www.schorsch.com/

Sent via Deja.com http://www.deja.com/
Before you buy.

[Steve Eckhardt]

In article <7url9o$g5h$1...@ssauraab-i-1.production.compuserve.com>,
kk...@compuserve.com says...

>Can somebody tell me what is the relationship between lumen and ANSI lumen?
>I have searched online and other encyclopedias, and the ANSI site but I
>couldn't find anything on ANSI lumen. How many ANSI lumen is equivalent to 1
>lumen?

>Thanks.
>Kelina

If you are referring to ANSI lumens as used in the projector industry, ANSI
lumens are defined as lumens output by a projector when measured according to
the applicable ANSI standard. For fixed resolution projectors, you need to use
ANSI/NAPM IT7.128, or for variable resolution (e.g. CRT) projectors, IT7.215.
Overhead projectors are measured according to IT7.204. In each of these
standards, the idea is to divide the screen up into 9 equal rectangles by a
tic-tac-toe pattern, measure the illuminance (in lux or footcandles) at the
center of each rectangle, average them, and multiply by the area of the light
patch on the screen. This gives ANSI lumens.
Manufacturers who do not quote ANSI lumens have been known to measure
the illuminance at the brightest point on the screen and then multiply by the
area. This can give a much higher number if the illumination is not uniform.
A similar swindle is now being used in plasma displays. One manufacturer
claims 350 "peak white nits". This is the display brighntess possible if only
a small area of the screen is illuminated. If you measure the luminance with
the entire screen white, you might get the same 70 nits we measured. (I have
to phrase it that way so the 3M lawyers can sleep at night, even though 3M
does not and should not take responsibility for what I say.)
--
Best Regards,
Steve Eckhardt (skeck...@mmm.com)

Opinions expressed herein are my own and may not represent those of my employer.