Vikas Sontakke
Enlightened
- Joined
- May 30, 2002
- Messages
- 860
What can we do to figure out relative brightness of a scene given the exposure information of the picture such f-stop, exposure time, ASA number and EV compensation data?
For example, intuitively
(f-stop) * (1/time) / ASA#
gives brightness value but it needs to be corrected if the EV compensation is not zero. Also the (f-stop) needs to be squared.
How about
(1 - EV_compensation) * { (f-stop)^2 * (1/time) / ASA# }
I can apply this formula to few beam shots from KD/DX and see if we come up with some way of estimating if a torch is indeed as bright as the picture suggests.
For example, some light show great full white beam but then you notice wide open aperture and 1600 ASA# and realize that in reality this light must be pretty dim.
I understand Lumens/Lux are supposed to tell me about the brightness but whatever gets listed on KD/DX site as Lumens/Lux numbers does not jive with my experience.
- Vikas
For example, intuitively
(f-stop) * (1/time) / ASA#
gives brightness value but it needs to be corrected if the EV compensation is not zero. Also the (f-stop) needs to be squared.
How about
(1 - EV_compensation) * { (f-stop)^2 * (1/time) / ASA# }
I can apply this formula to few beam shots from KD/DX and see if we come up with some way of estimating if a torch is indeed as bright as the picture suggests.
For example, some light show great full white beam but then you notice wide open aperture and 1600 ASA# and realize that in reality this light must be pretty dim.
I understand Lumens/Lux are supposed to tell me about the brightness but whatever gets listed on KD/DX site as Lumens/Lux numbers does not jive with my experience.
- Vikas
