Rollei Orange filter compensation

[JPD]

It's confusing. I spent a lot of time trying to understand these numbers decades ago. I usually use the f-stops that mnemosyne recommended:

yellow +1 stop
orange + 2 stops
red + 3 stops

I agree. The "filter factor" may be mathematically correct, but not intuitive.

Filter factor - Wikipedia

en.wikipedia.org

1.5 = 2/3 stop.
3 = 1 2/3 stops.

Stops are easier to remember, and one third of a stop doesn't make much difference for black and white for most uses, and one film can be a little more or less sensitive for different wavelengths of light than another.

 

[hiroh]

What about green? Also +1 stop?

 

[JPD]

What about green? Also +1 stop?

Yes. Then there is the light green that only needs a half stop.

 

[ic-racer]

It is all trial-and-error. The whole idea of a filter is to distort the film's sensitivity spectrum. Already, without the filter, most light meters are only a close approximation of film's sensitivity spectrum.