Filter Factor for HP5+ with yellow-green

[Pete Myers]

Dear Group:

Does any one have an opinion on what filter factor to use for incident light metering (daylight, landscape) for HP5+, using a Heliopan yellow-green filter? Heliopan suggests 2X (1-stop), but for example, TRi-X is speced at a filter factor of 4x for a yellow-green (tech pub F-4017) for daylight. Iford does not give a factor in its HP5+ data sheet, so hoping others might have a few comments based on their practical experience.

Pete

 

[Gumby]

In general following the "standard recommendations" for filter factors will work fine given the acceptable exposure breadth of B&W film. But you can't go wrong with following the Kodak recommendation either. They know their film and the specific spectral response of it. I don't know how that relates to Ilford products, though, which may not exactly match the same characteristics.

 

[Ed Bray]

I have used the following for many years, 1 Stop for Yellow, 1.5 Stops for Yellow/Green, 2 Stops for Orange and 3 Stops for Red. Usually they are not too far out.

 

[Pete Myers]

Thanks Ed--I appreciate your insight. Somehow 1 stop of filter factor did not quite grab me as enough and 2 stops likely too much for HP5+.

Pete