Polarizing Filters

[Shiva_42]

I've got to buy some new polarizing filters for existing and new lenses for my Nikon D90. All my previous Polarizers were linear, and I understand I need circular for my auto-focus stuff now...

Question 1: Will the circular still work as expected on my older film cams?
Question 2: I'd love to be able to buy the top-of-the-line multi-coated B+W or equivalent filters, but present income bracket won't allow it. What would be a really good brand for a selection of MC filters, but less expensive than this?

I'm probably thinking less than $100.00 for a 72mm Cir. Pol., and will need some smaller ones as well. I haven't kept up with technology the last few years, and don't know where to start.

Thanks!

 

[Overread20]

The only difference with a circular polarizer is you will have to turn the polarizer in order to vary the degree of polarization on the light entering the camera. So you can turn it from full to nothing - note that even with no polarization you will still lose the light entering the camera because of the filter.
Note that the ability to turn is part of the polarizer construction so it won't screw in/out of the filter thread as you turn it.

Also you can save money on filters by buying one topbrand filter for your largest filter thread size and then head over to ebay and get stepping rings so that you can fit the larger polarizer onto smaller filter threadded lenses. Generally speaking all your lose at this point is the ability to use a lens hood, but because of the need to rotate the filter itself you'll generally find that you're not using a hood with a polarizer. (if you do it can be a nightmare ).

For good brands B&W and Hoya are recommended brands - note that you want to make sure its a multicoated filter in the very least

 

[Garbz]

Q1: Yes. Will work as previously.
Q2: Hoya SHMC or Hoys Pro1 series are a bargain on ebay. Stay away from cheaper Hoya they are nasty, but the top of the range Hoya are IMO 95% of the B+W quality at like 50% of the price.

The only difference with a circular polarizer is you will have to turn the polarizer in order to vary the degree of polarization on the light entering the camera.

False. Common misconception of terms though. The terms circular and linear relates to the direction of the polarisation angle of the light coming out the back of the filter, not the action of the filter.

Incoming light is a mixture of polarisation angles circular, linear, etc. A Linear polariser will filter out linearly polarised light at a different polarisation angle than the angle of the very fine grid in the filter (the reflection off water has a linear component). But all light coming out of the back of a linear polariser is linear (which is why 2 linear polarisers stacked back to back will block ALL light).

The circular polariser is a linear polariser with a coating on the back that is 1/4wave of the light frequency. This causes the linearly polarised light into circular light again. So you still have the selective blocking of the linear filter, but the circular polarised light which allows the autofocus systems to work just fine.

 

[Shiva_42]

Decided to get the Hoya SMHC series, and couldn't be happier. I've also ordered the Cokin 100mm system to cover a variety of needs, and anxiously awaiting their arrival to try as well.

Thanks again for the good advice!