B&W CPL filter differences (KSM, EW)

[criza]

So I want to get a CPL filter, most probably a B&W, which they offer in 3 variations:

Normal
Kaesemann
Kaesemann EW

Anyone kind enough to tell me what the differences between these 3 filters are? Mostly between the Kaesemann and the Kaesemann EW?
Thanks in advance.

Regards
Chris

[neuroanatomist]

Normal is just that, except that there are actually two flavors of normal - one will have the MRC designation (multi-resistant coating), which is a multilayer coating that reduces reflections and is easier to clean. If there's no MRC in the name, it's just got a single layer coating. MRC is better (and more expensive).

Käsemann filters are the higher grade of CPL. Here's what B+W says about them: "This high quality polarizer is crafted from select polarizer foils and specially prepared optical glass. This neutral polarizer is edge sealed and therefore, it is durable under extreme climatic conditions." Käsemann filters are always MRC coated. Personally, I have Käsemann CPLs in both 77mm and 82mm sizes, in the Slim mount.

The Käsemann EW (or any B+W filter with an EW designation) is 'extra wide' meaning it's designed for ultrawide lenses. Basically, the glass is one size larger, and the filter combines a step-up ring in the mount. For example, a 77mm EW filter has 82mm diameter glass pieces but threads onto a 77mm filter thread - the larger glass means less chance of vignetting commonly seen on UWA lenses (where, to be honest, using polarizers is challenging due to uneven polarization at FF-equivalent 24mm and wider). Other options to redude vignetting are the Slim mount (thinnest option, lacks front threads) and the XS-Pro mount (still slim, but a little thicker and retains front threads for a lens cap).

Hope that helps...

[Busted Knuckles]

Buy whichever you want, BUT buy them from a no hassles return policy.

I bought something than the top of the line CPL and tested the impact on focus and sharpness - lets just say I tossed away the filter and the few dollars I thought I saved.

I now test every filter I buy the day it shows up on my two "best" lenses and anything other than "perfect" goes back before the UPS driver leaves the block.

Mike

[criza]

Normal is just that, except that there are actually two flavors of normal - one will have the MRC designation (multi-resistant coating), which is a multilayer coating that reduces reflections and is easier to clean. If there's no MRC in the name, it's just got a single layer coating. MRC is better (and more expensive).

Käsemann filters are the higher grade of CPL. Here's what B+W says about them: "This high quality polarizer is crafted from select polarizer foils and specially prepared optical glass. This neutral polarizer is edge sealed and therefore, it is durable under extreme climatic conditions." Käsemann filters are always MRC coated. Personally, I have Käsemann CPLs in both 77mm and 82mm sizes, in the Slim mount.

The Käsemann EW (or any B+W filter with an EW designation) is 'extra wide' meaning it's designed for ultrawide lenses. Basically, the glass is one size larger, and the filter combines a step-up ring in the mount. For example, a 77mm EW filter has 82mm diameter glass pieces but threads onto a 77mm filter thread - the larger glass means less chance of vignetting commonly seen on UWA lenses (where, to be honest, using polarizers is challenging due to uneven polarization at FF-equivalent 24mm and wider). Other options to redude vignetting are the Slim mount (thinnest option, lacks front threads) and the XS-Pro mount (still slim, but a little thicker and retains front threads for a lens cap).

Hope that helps...

Thanks for the very complete answer neuroanatomist! I will have to think about what to choose.

To some degree it's funny that I want a filter mainly for my 24mm glass (currently on a crop), meaning it's not UWA yet, but if I would go full frame it would be. So I guess the EW version can wait.

Another question evolved: I can use a step-up ring to mount a 77mm CPL filter on a 200mm lens, which has a 72mm thread, without any disadvantages? Would be nice to spare some money..

[Dr Croubie]

Another question evolved: I can use a step-up ring to mount a 77mm CPL filter on a 200mm lens, which has a 72mm thread, without any disadvantages? Would be nice to spare some money..

How much do you like hoods?
I can mount a 72mm CPL on my 67mm-threaded 70-300L with a 67-72mm step up ring.
But, I have to mount the hood first, then the step-up-ring and CPL. Dismantling, I have to unscrew the CPL and step-ring first, then take the hood off, and sometimes that's been a bit scary when i couldn't get the filter off easily (and couldn't get filter wrenches in there because of the hood).
In short, I gave up and bought a 67mm KSM CPL. It is still hard to adjust the CPL with the hood on, but at least I can get the hood on and off without touching the filters...

[Sean Setters]

Personally, I like buying decent quality 77mm filters (the largest that I currently need) and using setup up rings with them. Step up rings are cheap and allow you to use the same filter across multiple lenses. I think that's just brilliant and economically sound--but I'm cheap when it comes to most things.

[criza]

Personally, I have Käsemann CPLs in both 77mm and 82mm sizes, in the Slim mount.

Is there any special reason you are using slim mount CPL filters, and not the regular ones? Thanks in advance.

[neuroanatomist]

Is there any special reason you are using slim mount CPL filters, and not the regular ones? Thanks in advance.

Reduced likelihood of vignetting. With some lenses, it doesn't matter, but with others, it does. Sometimes I'm in a hurry to catch a shot, and I just stack the CPL on the UV filter already on the lens, instead of swapping them. I'm not bothered by the lack of front thread on the CPLs, I only mount them when I'm using them so no need for a cap.