Which polarizing filter, linear or circular??

[User_2019667]

What type of polarizing filter should I use on my Minolta X-370

manual focus camera? Linear or circular?

John Pender

[dave_osborne]

Either if it's manual focus. You only need to worry if you've got autofocus (in which case you would use circular).

[rdkirk]

A camera requires a circular polarizer if it uses a semi-silvered mirror in the light path of either the focusing or metering systems.

 

A linear polarizer polarized the light by removing all waves not vibrating in the polarizer's set direction). Then, a semi-silvered mirror attempts to polarize it again--most likely in a different direction--which filters out all or most of the remaining light.

 

A circular polarizers applies a "quarter twist" to the light after polarizing it so that it's not affected further by any semi-silvered mirrors in its path.

 

Most modern SLRs and DSLRs do have semi-silvered mirrors. Most P&S digitals and most many manual focusing SLRs do not.

[pvp]

It might require a CP due to the metering system. Fact is, a circular polarizer will work on absolutely ANY camera, while linear polarizers can have problems in some cases. There is no difference in the effect on the image. If there's any doubt, just get a CP and no worries.

[discpad]

Kirk's analysis is spot-on; and Alan's advice to use a CPOL filter is also quite correct.

 

[Like an alley-oop: The guard throws the ball near the basket, and the center slams it home.]

[dave_osborne]

Just curious - which manual focus metering systems require a circular polarizer?

[discpad]

Super Dave,

 

Most all manual focus SLR's that have metering: In fact, screwing up the metering is the more serious issue when using a linear polarizer.

 

 

Here's a test you can try: Put a linear polarizer on your SLR and set it to manual, so you can read the light level. Point it at a light source and rotate the linear polarizer ring, and watch the indicator in the viewfinder swing.

 

In fact, in a pinch you can use a linear polarizer, provided you mark on the lens barrel where the meter is reading the absolute maximum... But, if you have to ask... DON'T DO IT!

[Matthew Currie]

The X-370 does not have a semi-silvered mirror. You can use a linear polarizer. I just confirmed this on mine. The mirror has an opaque metal back, and turning the polarizer has no effect on the meter reading.

[richard_cochran]

<cite>Just curious - which manual focus metering systems require a circular polarizer?</cite>

<p>

Very few. The only ones I can think of offhand are the pellicle mirror cameras. These replaced the bouncing movable mirror of a conventional SLR with a fixed semi-silvered mirror, mostly in order to avoid the speed penalty of having to flip the mirror up and down with each shot. The downside was a dim viewfinder and less light reaching the film, since the light going through the lens was always divided between the viewfinder and film. Nikon made special high speed motorized versions of the F, <a href="http://www.mir.com.my/rb/photography/hardwares/classics/nikonf2/rjohnson/nikonf2h.htm">F2</a> and <a href="http://www.mir.com.my/rb/photography/hardwares/classics/nikonf3ver2/variations/f3hspeed/">F3</a> using this strategy. Canon made similar high speed versions of its F1 and F1n. The <a href="http://www.mir.com.my/rb/photography/companies/canon/fdresources/pellix/">Canon Pellix</a> was a more common "pedestrian" camera that also used a pellicle mirror.

<p>

There were a couple of other manual focus cameras with a semi-silvered mirror in the metering path, but that practice didn't become really common until autofocus.