Question re: filter factor

[Hibbs]

Ok...here is the scenario. I am trying to figure out the the filter factor for using film in a totally automatic camera.

The camera is an Olympus Pen EED. Meter is outside of filter ring.
The filter is a Red 25A.
The film is Ilford Delta 3200.​

If I wanted to expose the film @ ISO-1000, should I set the Pen EED @ 125 given that the filter factor of 8 requires 3 full stops.

1000 X ½ = 500

500 X ½ = 250

250 X ½ =125​

Is this correct?...or does anyone have another suggestion.

Also...if I wanted to use something like Kodak BW400CN rated at 250 w/ the red filter, I'd set the EED at ISO 30?

Thanks for any encouragement here...just havin' a bit of fun!
~hibbs

 

[Pherdinand]

correct...

 

[spyder2000]

The simplest way is to divide the exposure index by the filter factor. The result is the EI setting for the camera or meter.

 

[eli griggs]

Does anyone here know of a good filter factor calculator that can be downloaded and printed/assembled like a sliderule?

Eli