View Full Version : Filter Factors

Paul Mongillo
28-Apr-1999, 14:45
I recently purchased a Cokin filter system for B+W 4X5 photography. I got the 0 01 yellow, 002 orange, 003 red, 004 green and 160 polarizing filters. Simple en ough. However, things seem to always be more complicated. No literature came w ith them. Therefore no info was provided on how to contact Cokin with questions . I don't even know what country they are located in. I tried and e-mail searc h and the 1-800 operator, but to no avail. Does anyone know how to get ahold of Cokin or would any of you like to try to address my questions ?

1. Cokin provided no filter factor for the polarizer. I put it on my spot meter and found a 2 f stop decrease. This matches some literature, but others say a bit more. OK on this one I guess other than Cokin gave no indication of what it should be.

2. The yellow filter factor provided on its plastic container is 13 f stop. I cannot find any standard yellow filter that matches this. I put it on my spot me ter and found it reduced exposure by 2/3 f stop which is standard for a number 6 yellow filter . Anybody know whats going on here ?

3. Cokin indicates on the orange filter container that the f stop adjustment is 1. This does not match any in the literature I have. I put it on my spot mete r and found nearly a 2 1/3 f stop difference which matches a number 21 orange. Any ideas ?

4. OK on the green and red. Cokins f stop recommendations match my meter and t he literature.

5. While trying to figure all of this out, I noticed that the recommended filte r factor adjustments are different for some filters for Tri-x and T- max. I'm t otally confused now.

Charles Matter
28-Apr-1999, 15:14
Cokin filters, (I believe) are made in France..but get hold of the B&H Source book. They list suggested filter factors in the Cokin listings, as well as a host of other useful information. Calumet catalogue does the same. The polarizer FF will vary according to how it's rotated, which will darken and lighten according to the relationship of the reflection, or light angle to the axis of the filter. Take the filter and look thru it as you hold it up to blue sky. Turn it and watch what happens. The different ff's for different film dosen't surprise me. All panchromatic emulsions will vary slightly in their color response, especially red. Use the values you have as starting points and fine tune as you shoot

William Marderness
28-Apr-1999, 15:43
Polarizers in general require a 1 1/3 stop increase. I have been using this with my 4x5 regardless of the filter's rotation with good results. I don't know about Cokin filters first hand. (Why are you using Cokin? The quality is questionable.) I suspect that the Yellow is an 8 and the orange a 15. Try matching them to Tiffen 8 and 15's (which can be found in most camera stores). Tiffens match Kodak Wrattens.

William Marderness
28-Apr-1999, 17:03
The filter factor for yellow and dark yellow filters is less for Tmax than for Tri-X because Tmax is less sensitive to blue than Tri-X.