Marumi DHG circular polariser

'lo All

Just wondering if anyone has a Marumi DHG circular polariser. I understand these represent pretty good value for money:

http://lenstip.com/115.4-article-Polarizing_filters_test_Results_and_summary.htm...

Currently I have a linear polariser which works reasonably well. Now, I don't want to re-open a conversation about whether linear polarisers work with Pentax DLSRs or not. I don't seem to get lots of problems with the metering but I haven't tested it extensively so it could be my inexperience or that the difference is too small for me to notice.

The main reason I am considering getting a circular polariser is to use it alongside the linear polariser as a variable ND. I've not tried it out but apparently if you mount a linear polariser on top of a circular polariser you can vary the amount of light you let through. The Marumi is relatively thin and my linear polariser is really thin so vignetting would hopefully be minimal.

Since the Marumi is good value I figure I can't really lose (well, not more than £30 and even then I get a circular polariser to replace the linear one and therefore if there are some metering issues I'm not noticing then it will eliminate them).

However, I was wondering if the Marumi has a filter mounting thread on it. I believe some polarisers don't and therefore that would prevent me using it this way.

So, in a roundabout way my question is "does the Marumi have a thread to mount a second filter on it?". Anyone know?

Cheers,

WG

I have used Marumi for a good few years. They were introduced into Bahrain whilst I was there. They work well and have the thread on the front to accept others. Still worth an email to the importer to verify though.

Some data here and contact link.

link

Regards

You sure, I thought you need two if the same type...

http://www.digitalphoton.net/making-a-variable-nd-filter-with-circular-polarizer...
You might want to take a look at LCW Fader, those aren't that expensive.

Thanks for the info K10d. Reassuring to know someone else uses Marumis with good results.

Stefan, I have to admit I don't really understand the explanation in the link. However, my understanding of polarisers is very basic. I would have thought a circular polariser attached backwards would act as a linear polariser. Would the light not pass through the quarter wave plate first and then be polarised by the front plate? Anyway, I hadn't thought about the fact you would get a polarised effect. Having a think about it, I don't think that is too much of a problem for me.

I'm tempted to give it a go and see how I get on.

Cheers

wg

Well my Marumi filter turned up. Haven't had much chance to use it yet but it seems a solid piece of kit and nice and slim. It does indeed have a thread at the front for affixing another filter so I was all go to try out the variable ND effect...

... but nothing happened.

The image went from polarised to not polarised but I couldn't vary the light coming in at all, never mind blocking out incoming light entirely.

The only answer I could come up with was that my "linear" polariser was actually a circular polariser. I turned the filter around and held it in place and, sure enough, it gave the effect I wanted.

A bit more searching on the internet and it turns out that the Panasonic DMW LPL 72 may actually be a circular polariser. When I bought it I'd looked and all evidence seemed to suggest the LPL meant it was linear. Panasonic's website now lists it as cicular so that must be right.

As an aside this may explain why I never got any exposure problems with a linear polariser...

This bit of good news leaves me in a pickle as I can't use the filters together the way I wanted to. I could try and get a macro coupler but finding a 72/72 seems tricky and this would probably add to any vignetting as the filters would be further apart. I could try and take one apart and reverse the glass but that seems a fine way to ruin a decent circular polariser. The last option is to source a linear polariser. Extra cost unless someone wants to swap a 72mm linear for a 72mm cirular.

Frustrating

WG

You will never cut out all the light with one polariser, you need two for that. You also need the light to actually be polarised for any effect, and not all light is polarised.

I've tried this trick. Even with the two best polarisers together, I still got a cross in the centre (ie irregular darkening). If someone else can make it work, great, didn't work for me though, sadly.

WobblyGoblin, that's right, a linear polariser is just a backwards circular one.