Given an original speed and the Stop value of the attached NF filter, it calculates final exposure time. http://www.vassilistangoulis.com/gr/?p=4958 Tnd = T0 * 2^ND where:
- ND is the Stop value of your ND filter
- T0 is the Base shutter speed (without filter attached) in seconds
- Tnd is the final exposure time
https://photo.stackexchange.com/questions/32359/why-does-ev-increase-as-iso-increases the log2(100/S) is wrong on that link! The correct formula appears in Wikipedia https://en.wikipedia.org/wiki/Exposure_value
EV = log2(N²) + log2(1/t) - log2(S/100) EV = aperture + shutter - ISO
t = SN²/1002^EV
- where:
- N is the relative aperture (f-number)
- t is the exposure time ("shutter speed") in seconds[2]
- 100 is the default ISO
- S is the new ISO
https://photo.stackexchange.com/questions/32359/why-does-ev-increase-as-iso-increases the log2(100/S) is wrong on that link! EV = log2(N²) + log2(1/t) - log2(S/100) EV = aperture + shutter - ISO https://photo.stackexchange.com/questions/73304/when-to-use-the-lv-formula Another way to look at it EV = log2(f^2/T) Exposure Value LV = EV + log2(ISO/100) Light Value (= EV assumes ISO 100)