Different Angle on Polarizing Filter

[Denniscasey]

I was going to buy B+W single coated polarizing filter that said "single coating boosts light transmission." Then I read posts saying in bright sunlight HMC40 built in ND filter may not reduce light transmission enough --iris can not open enough to reach optimum level.

So since I use polarizing filter in bright sunlight I compared B+W single coated, B&W model BWCP43 (not single coated) and Format Hi Def circular polarizing filter. But they all had same filter factor of 1.3. I understand filter factor to mean f stop opening needed to get same light as without filter. So, am I right that all three of these filters with 1.3 filter factor has same light transmission? I read all 8 pages of filter sub-forum and did not see reference to this angle of using polarizing filter to reduce light transmission to help HMC40 work better in bright sunlight (besides other benefits of polarizing filters).

 

[nosys70]

seems you loose at best 1.3 stop (and as much as 2 stops) when using these filters.
probably a generic number that is very variable at each particular setup.
coating decrease reflection of light between the glass layers, so it improvevement is more
visible on the quality picture (mostly flare and haze) than light transmission

 

[Felipe Henao]

I was going to buy B+W single coated polarizing filter that said "single coating boosts light transmission." Then I read posts saying in bright sunlight HMC40 built in ND filter may not reduce light transmission enough --iris can not open enough to reach optimum level.

So since I use polarizing filter in bright sunlight I compared B+W single coated, B&W model BWCP43 (not single coated) and Format Hi Def circular polarizing filter. But they all had same filter factor of 1.3. I understand filter factor to mean f stop opening needed to get same light as without filter. So, am I right that all three of these filters with 1.3 filter factor has same light transmission? I read all 8 pages of filter sub-forum and did not see reference to this angle of using polarizing filter to reduce light transmission to help HMC40 work better in bright sunlight (besides other benefits of polarizing filters).

Polarizing filter not only affects light transmission but color and contrast also, if your target is light transmission go with ND , B+W by Schneider are very good.

 

[Denniscasey]

Polarizing filter not only affects light transmission but color and contrast also, if your target is light transmission go with ND , B+W by Schneider are very good.

Thank you Felipe and I recall your earlier post regarding how polarizing filters affect color and contrast also. I understand in bright sunlight actually good to reduce light transmission for HMC40 and you are right about using "add on" ND filter for that in most cases. However, in those cases where I would use a polarizing filter for the "look" it gives I was also wondering if the data published for each filter ( the "filter factor") would tell me reduction in light transmission. And I understand now the information that nosys70 pointed out in his reply.

 

[Denniscasey]

seems you loose at best 1.3 stop (and as much as 2 stops) when using these filters.
probably a generic number that is very variable at each particular setup.
coating decrease reflection of light between the glass layers, so it improvevement is more
visible on the quality picture (mostly flare and haze) than light transmission

Thank you and very helpful to increase my understanding of this including how the light transmission would vary with different amounts of polarization (why polarizing filter shows different levels of "darkness" when you turn it).