Filter Factors

[pemongillo]

I recently purchased a Cokin filter system for B+W 4X5 photography. I got the 001 yellow, 002 orange, 003 red, 004 green and 160 polarizing filters. Simple enough. However, things seem to always be more complicated. No literature came with 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 search 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 ?

 

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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.

 

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2. The yellow filter factor provided on its plastic container is 1\3 f stop. I cannot find any standard yellow filter that matches this. I put it on my spot meter 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 ?

 

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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 meter and found nearly a 2 1/3 f stop difference which matches a number 21 orange. Any ideas ?

 

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

 

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

[c_matter1]

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]

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]

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.