Problem using polarizer on MX300.

[florian otel]

Basically this is a cross-post from dv.com. Appologies for that, but maybe someone here has a decent technical explanation for a change...


Again: The story was that originally I was trying to use the Pana wide-angle adaptor w/ a polarizer on my Pana MX300. When mounting a Hoya 72mm Circ. Pol. in front of the adaptor I got color aberations: lower right corner turned redissh, lower left corner turned greenish, like this:

http://www.ce.chalmers.se/staff/otel...aberations.jpg


Now, after getting a 43mm polarizer, mounted between the camera and the wide angle, I get the same effect, except that the hues are reversed and spreaded over the whole image, not only the lower half: The lower right and top left quarters turned greenish (as opposed to redish above), lower left and top right corder are reddish (as opposed to greenish above).

As other have suggested (thanks Frank!) the basic conclusion is "forget using this adaptor with a polarizer" (It works perfectly well w/ a warmer filter, but that's beside the point).

The adaptor issue beeing moot now, what really worries me is that I get the EXACT effect as the second above when using the polarizer WITHOUT the wide-angle adaptor. And that is disregarding _how_ I mount the filter -- directly on the lens thread or on the rubber hood thread -- I still get the color aberations.

On a side note, the effect is most vissible when using manual white balance and set for a bit "warmer" colors. Also, it is less visible when there is no direct sunlight on the filmed object.

Now, while I can accept that the adaptor cannot be used with a polarizer, being crippled and not being able to use a polarizer AT ALL with the camera, it's a bit more than I can digest....

So, my question is: Anyone, any idea on what could be the cause and/or how to fix it ?


Thanks,

Florian

P.S. Questions to moderators: What do I have to do to be able to attach images to my posts ? Did read the FAQ but I'm not allowed any attachments. And no [img] tag either. TIA...

[Frank Granovski]

I thought I explained about your problem over at the other forum. Anyways, I've discovered that there is a real problem with using filters on wide angle adaptors. You will almost always get some vignetting (what you call aberations). This is perhaps why so many brands of wide angle lenses do not come with filter threads. I know you don't like this, and neither do I.

I've discovered that Tiffen makes a very good 43mm wide angle with threads, but as Terrence explained on the other thread, the Panasonic is probably the best wide angle for your cam. I think that you should just forget putting a filter in front of the wide angle. But, if some filters work this way for you, then keep using them.

Regarding the circular polarizer, just forget it. Make due with your adaptor's hood. I know this isn't the best solution, and you won't get rid of the reflections, but it will help with the streaking/reflections you get from not using a hood.

With putting the polarizer between the camera's lens and lens adaptor, I don't think the polarizer will work. That's because the glare is already coming through the adaptor, which is basically 1/2 of your cam's lens (with the adaptor attached).

If you keep trying to make this work somehow, the more frustration you will encounter - with always the same results: aberations. I e-mailed Terrence, perhaps he can tackle this further. (I'm going to have a look at that Tiffen wide angle later today. I'll let you know what I think of it, for the MX300/0).

By the way, nice picture!

[florian otel]

Frank, I'm not sure I got my message through, even the second time.

This is NOT about the adaptor anylonger. Forget the adaptor, I got that message right the first time (well, maybe second ;)).

I have vignetting when using the polarizer on the camera itself WITH NO ADAPTOR WHATSOEVER. Just the 43mm polarizer on the camera lens. That's my problem.

P.S. That web site was down for a bit..

[Frank Granovski]

Sorry. I guess I didn't understand the question. You're getting vignetting from the 43mm filter. Is the filter a "slim line?" Is it fat and does it stick out? If this is the case the filter is too far from the lens. The other thing that comes to mind is that the filter itself is faulty. Did you try shooting with both the filter and rubber lens hood? The lack of a hood may cause streaks.

[Chris Hurd]

Hi Florian,

I chose not to allow the posting of images in order to keep the overall bandwidth down. The only bad thing about this forum software is that it's based on tables; some fairly complex tables have to load in order to display the page. The bandwidth is a little too much (the pages load a bit too slowly) for my tastes, and images would slow it down even further.

If you don't have a site that you can upload your sample images to, you could e-mail a couple of them to me and I can probably do it for you from my site. The images should be 640x480 with no more than 20% compression. Hope this helps,

[Andre De Clercq]

Although I try people to convince that circ polarizer are not needed in video camcorders and just linears can do a perfect job, there are a couple of problems which you can get IF SOMETHING ELSE IN THE OPTICAL PATH IS WRONG. Plse inform whether yr camera is a 3CCD or not. Secondly doublecheck if yr polar is really circular with the retarder on the right side. You can do this by looking through your polarizer into a mirror from both filter sides. If you look through the filters' frontside it should look opaque (black) if yr polar is a circ one.

[Tim Selander]

Hi dre.... stumbled on your post. Would be very interested in hearing why linear pol. works as well as circular for video cameras. Florian's camera is a 3CCD, and coincidently, yesterday someone with the same camera was asking me about polarizers. I told him to go with circular -- a bum steer?

[Andre De Clercq]

It's a general misconception that you would need circular polar for camcorders. Only for some photograhic camera's (SLR...) which contain polarisation sensitive elements in the measuring path depolarising incoming light is a must, That's what a circular polarizer does with it's retarder plate. With camcorders,nor the main optical path, nor the sensing for gain control,focus,..contain any polarisation effect...did you ever see the "bleu sky" become deeper bleu when rotating your camera...no? then it doesn't show any polar effect by itself and thus is polorisation insensitive. However, if the optics show birefrengence and/or the color spliiting dichroic prism is not uniform, all kinds of polarisation rotation occur which can end up in colored shades if a linear or eliptical polar is being used...

[florian otel]

dre,

First of all, thanks for the insight. I was aware of the fact that a circular polarizer is not really needed since -- and this was my vague understanding before reading your post -- the whole idea of circular polarizers was that linear ones used to interfere with the TTL metering system of SLR cameras since those employ mirrors.

However, the choice of the polarizer was actually beyond me: Despite that I would have preferred a cheaper linear polarizer, the local shop had only two types of polarizers in 43mm: Soligor circular and Hoya circular. I went for the former since it was cheaper..

Second, as Tim said (thanks Tim -- yet again) the Pana MX300 (mentioned in my previous posts) is indeed a 3 chipper. What puzzels me the most is that, with it being a popular camcorder, I've heard quite a few people using polarizers with it but none complained about vignetting (or "color aberations" as I used to call it -- I though vignetting pertains only to corner darkening..)

I will try to check if the polarizer is really circular, using the method you described. While I have no reason to doubt the seriousness of the store I've bought it from, it might worth a double check. I still don't get how it would help though. Barred the mishap that indeed it is not a circular and the color-splitting prism in my camcorder is non-uniform, which is a long, long shot...


Anyway, many thanks for the tips and the technicalities. Now THIS is what I thought a forum about DV cameras technicalities should be like :-)

Cheers,

Florian

[florian otel]

Tim,

I have a short question: Since apparently the "Soligor" brand of my circular polarizer is Japanese I was wondering if you ever heard / encountered this brand of filters/polarizers there in land-of-the-good-sushi :)

Seriously now, I think I have two choices:

1) This Soligor polarizer is a crappy one and I should exchange it for a Hoya and hope that one behaves better.

2) Shake my shoulders, deploy my fate, forget using a polarizer of any sort in my MX300 and return it for a refund.

Thanks,

Florian

[florian otel]

Chris,

Thanks for the explanation. No problem posting images on other sites. While I can completely understand the undesirability of attachements due to bandwidth limatations (afterall this is a community service you're doing and its your own bandwidth we're consuming -- for free), it's a bit of a PITA not being able of using [img] tags to link to external sites. Now _that_ shouldn't consume _your_ bandwidth ? Or there is smth else escaping me?

Thanks again,

Florian

[Frank Granovski]

Florian,

I use a Cokin circular polarizer (43mm). I haven't noticed the problem you describe. I've always had good luck with Cokins, Heliopans and B+Ws. My favourites are still the Cokins. They work well, they have a large selection, and they are inexpensive.

[florian otel]

Yes Frank, we both know you're a Cokin fan :) Remeber, I tried myself to get some Cokins (i even sent you a mail about that...) but in this dark corner of Europe Cokins are not the cheapest I can get, unfortunately. And, to be honest, I'm not sure if ever changing polarizers would help....

Anyway, I think I will take my chances with the Hoya. If that one doesn't work, that's it. Until next time :)

Thanks,

Florian

[Andre De Clercq]

I am not convinced you have a bad performing polar. Just keep it in front of another camcorder and see what happens... I don't know if the MX 300 contains (internal) acrylic lensparts, but they are very sensitive to birefrengence if mechanically stressed. I think this is the most plausible reason for your problem. In this case, even a circ polar cannot avoid colorshades. I would advise to send this cam back...Keep in mind that "living without polar" is not a good solution because, even without polar, the (polarised) blue sky or window reflections can still result in unwanted colorshades

[Frank Granovski]

The Cokin polarizer is brought into North America by Minolta. It's their speciaty filters which are difficult to get. That should change soon, though.

The other member brought up an interesting possibilty. (It could be a problem with your cam.)

Yes, I'm a Cokin fan, but I own many filter brands for my SLRs.