See a split screen when using circular Polarizer

[bob_tourdot]

<p>Hello,</p>

<p>There's a phenomena I don't understand and I wonder whether anyone can explain it for me. When using a circular polarizer outside, while rotating the polarizer and looking through the optical viewfinder of slrs, often the view through the viewfinder seems to split into a dark half and a light half instead of the normal intensification and reduction of the polarizing effect with rotation. This doesn't happen all the time, and I thought it might be that I was using a linear polarizer instead of a circular one, but this happens with different lenses, polarizers, and cameras. This may be a simple question but I'm baffled.</p>

[henryp]

<p>The split image portion of a camera's focus screen needs an effective max aperture of f/5.6 or brighter or you have to be VERY careful to make sure you eye is dead-on in the optical center of the field of view. if you add a pol filter to a zoom with a max aperture of (for example) f/4-5.6, the filter factor makes the effective max aperture smaller than f/5.6.</p>

<p>So the solution is to move your eye side-to-side until you hit that sweet spot and/or to avoid using filters with high filter factors with relatively slow lenses. Hobson's choice.</p>

<p>Henry Posner<br /> <strong>B&H Photo-Video</strong></p>

[Ed_Ingold]

<p>A polarizer has no effect on a split-prism viewing screen. While the filter affects exposure (q.v., filter factor), it has no effect on the diameter of the aperture, which must be greater than f/5.6 for the rangefinder to function. The rangefinder is also fussier when a longer than normal lens is used, regardless of aperture.</p>

[bob_tourdot]

<p>Thank You</p>