I meter a surface at ASA 100 and get F4 at 1/15 second. What is the illumination coming off that surface in Cd/square foot ?

  • 1
    \$\begingroup\$ Probably best asking this on physics.stackexchange \$\endgroup\$
    – MikeW
    Commented May 26, 2013 at 0:00
  • \$\begingroup\$ Maybe How to calculate Lux from EV? \$\endgroup\$
    – mattdm
    Commented May 26, 2013 at 4:43
  • \$\begingroup\$ I think the linked question contains the information you're looking for. \$\endgroup\$
    – Joanne C
    Commented May 27, 2013 at 0:44

1 Answer 1


This Kodak reference for estimating luminance and illuminance may help.

Your metering at ISO 100, 1/15th and f/4 would be equivalent to ISO 400, 1/30th and f/5.6 if I've done the math correctly. So use their value for f/5.6 which is 2.67 Cd/ft2


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