Polarizing Filter (Circular)

[LarryRz]

Since we've had lots of bright sun in Chicago this summer I've been getting pictures with lots of bright, reflective areas and dark shadows. Lots of glare as well.

Recently I purchased a circular polarizing filter (B+W) for my G1 with 58mm adapter.

I have several basic (hopefully not to dumb) questions on the correct usage of this piece of equipment.

1. The filter can be rotated once it is screwed onto the LA-DC58. I can't see any difference when I rotate it, not like when I rotate my sunglasses. Why would a circular polarizer care what rotation is is at? I can understand why one would desire to rotate a linear polarizer. So, what am I supposed to be doing here?

2. The polarizing filter has threads on the outboard end to, I assume, allow attachment of another device (filter or lens?). Is it appropriate to attach a skylight filter or UV filter to the front of a polarizer? How about a teleconverter...?

3. When I use my teleconverter, Canon TC-DC58 should it be positioned closest to the camera, farthest from the camera, or doesn't matter?

Thanks for help with these questions. I'll probably end up with a few more.

Uncle Lar

Chicago

[henkbos]

Hi Uncle,

Got filters as well and I do see the effect (both on EOS500 and on D30). Different brand though but that shouldn't matter.

As for the threads: I guess that the pol-filter should be as much in the front as possible like you would use clip-on sun glasses if you were glasses.

Good luck

[Eric F.]

Hi Larry,

I also have a circular polarizer which I have been using with my G2, expermenting from time to time. I really did not know exactly what I was doing, but every once in a while I would get a very much improved picture. Most notable was Blue skies and some colors.

Saw a article in September 2002 issue of Popular Photography magaizine on "HOW TO MAKE YOUR POLARIZER DO WHAT YOU WANT!" I think I now understand how and why these things work. Of course the article is 5 pages long with pictures and diagrams so you will most likely need to find a copy and read it but I will atempt to give you the highlights. :)

1. A linear polarizer must be turned to work, because the "magic angle" is 30 degrees. That is why you see it darken as you turn it, because the angle to the light is changing. In a circular polarizer, you will not see the same effect while turning, but you will see "and need to be aware" a difference in your lenses angle to the light. There is a handy way of easily doing this with you thumb and finger shown in the article.

2. The threads are for attaching other lenses on it. The article stated that it was important to make sure that the basic filter was clear or neutral gray, but that some places warming filters improved the pictures. I have used my teleconverter attached successfully.

3. I think that your filter would have to go between the adapter and the teleconverter, unless you have a large one that would fit on the outside which would be a lot more expensive.

It would worth your time to find a copy of the magizine, then you could answer everyone elses questions. :)

Hope this helps.

[Sheila]

My polarising filter is also attached to the skylight filter on my D60. Polarising filters only work at a certain angle to the sun - I believe it is 90 degrees more or less. I could not live without this filter here in Sydney where the lighting is extremely bright (more or less due to lack of pollution). But I never use it on a long lens as it cuts down too much light (about 2 stops I believe) and always take it off when shooting with flash.

Hope this helps.
Cheers
Sheila

[LarryRz]

Thanks everyone...this thread was quite old so I was surprised to hear from y'all!

I'll watch http://www.popphoto.com/ for the September issue articles. I've seen others (Fred Miranda comes to mind) about polarizers so I have been using mine to advantage. I now know how to align the rim for best effect.

Of course when I turn the camera to portrait orientation I have to remember to turn the polarizer as well!

I'm still shooting away with my G1; over 22,000 now and a few keepers. I'd be broke if I had to buy all that film and developing!

Some stuff is at:

http://www.pbase.com/larryrz

Larry

[ken-w]

LarryRz wrote:

1. The filter can be rotated once it is screwed onto the LA-DC58. I can't see any difference when I rotate it, not like when I rotate my sunglasses. Why would a circular polarizer care what rotation is is at? I can understand why one would desire to rotate a linear polarizer. So, what am I supposed to be doing here?


Hi Larry - I'll add my 2-cents here. All polarizers work the same way and all have to be rotated to achieve the proper polarizing effect. Circular polarizers (not to be confused with round polarizers - since both linear and circular are round with a rotatable ring and look identical). A circular polarizer has a second layer that transforms linearly polarized light into circularly polarized light which is needed for some SLRs (with beam splitters) to focus properly. The Canon G1 and G2 will work equally well with either a linear or circular polarizer.

Maximum polarizing effect is achieved looking 90º away from the sun (i.e. your shoulders in line with the sun). If you are shooting into the sun or 180º away from the sun you will see no polarizing effect. You must use your LCD viewfinder to see the polarizing effect (since the optical viewfinder doesn't look through the lens). A hint is to hold down the shutter button to lock in exposure and then rotate the ring. If you don't do this, the camera will compensate for the exposure difference between non to full polarization and the optimal polarization spot will be harder to see. Another hint is to aim the camera at something that will show maximum polizaring effect (i.e. blue sky). Once you have the ring in the right position, recompose and re-expose your shot and take the picture. The use of exposure bracketing is also highly recommended.


2. The polarizing filter has threads on the outboard end to, I assume, allow attachment of another device (filter or lens?). Is it appropriate to attach a skylight filter or UV filter to the front of a polarizer? How about a teleconverter...?


Most filters can be stacked using the outboard threads. For instance I often use a polarizer in conjunction with an infrared R72 filter. There are two issues regarding stacking filters. The first is that the more glass you add, the greater the possible optical degradation, even with clean filters. The second is possible vignetting (round borders at the edges of your photos when the lens sees the outside corners of your filter). This isn't much of an issue if use the 58mm adapter since it is much wider than the lens size.


3. When I use my teleconverter, Canon TC-DC58 should it be positioned closest to the camera, farthest from the camera, or doesn't matter?


Since the TC-DC58 doesn't have outboard threads the only option is to position it as the outermost piece.

Happy polarizing.