Polarizing Filters and Contrast-Detect Focus

[lobalobo]

<p>Does a digital camera with a contract-detect auto-focus (such as the Fuji s6000fd bridge camera or the Panasonic G1 micro 4:3 "EVIL" camera) require a circular polarizing filter, or is a linear as good or better? A linear is cheaper and my understanding superior in manual focus analog cameras, but that they disable phase-detect autofocus in SLRs. What's the answer for a contrast-detect focus, though? Thanks in advance.</p>

[William Kahn]

<p>Linear polarizers tend to confuse autofocus functions. That's why circular polarizers were invented. I'm not familiar with "contrast-detect" focus, but if it's essentially an autofocus function, there will probably be a problem with a linear polarizer. Why not contact Panasonic and ask them?</p>

[peterblaise]

<p>.</p>

<p>Nope, any polarizer will do if there's no silvered mirror splitting the image "beam" -- as has been true for the last 10-sum-odd years of non-DSLR-digicam photography and longer than that for non-mirrored auto focus cameras like pocket compacts.</p>

<p>Even with a silvered mirror beam splitter, it's up to the alignment of the polarizer and the sensors to fight or cooperate, so sometimes linear polarizers appear to work just fine on auto focus SLRs. Go figure.</p>

<p>Try both, have fun, let us know what works, and share some pictures!</p>

<p>----------</p>

<p>And I think of the <strong>2008 Panasonic Lumix DMC-G1</strong> as a <strong>DSL/EVF</strong> <em>Digital Single Lens Electronic View Finder</em> camera, though I understand wanting to include the "I" as in "Interchangeable" lens, something nobody <em>ever </em> did for SLRs, never calling them SILR cameras for Single Interchangeable Lens Reflex cameras (pronounced "sillier" camera?), so why start now? I suppose we could start a preference war between cameras nicknamed "EVIL" and "SILLIER". Go for it.</p>

<p>.</p>

[davidlong]

Contrast-detect AF is fine with a linear polarizer, since it works just what on what the sensor sees. The only conceivable difference between a linear and circular polarizer in such a camera is the light's interaction with the birefringent anti-aliasing filter that sits on top of most Bayer sensor arrays. Any effect from that is likely to be tiny if it's detectable at all.