I got this Zeiss 354/0 Orange 5X S 40.5mm filter, but can't find any information about it. Also filter looks like it has some coating on it.
Does anyone know what filter factor it has and how should I adjust my exposure when using it?
The 5X should be the filter factor. Multiply the exposure by a factor of 5. That's 2.3 stops. To get stops from a filter factor, usually shown as 1.1X, 1.5X, 2X, 4X, 8X, 16X, i.e. a number followed by 'X' marked on the filter bezel use:
Originally Posted by tvora
stops = log(filter factor)/log(2)
both logs should be in the same base