This is huge: A Geek’s Guide to Pentax’s *switchable* low-pass filter

by Dave Etchells

posted Monday, October 7, 2013 at 8:19 PM EDT


We don't normally post a separate news story when a new camera model brings a new technology along with it, but Pentax's new mechanical anti-aliasing filter simulator is so revolutionary that it more than deserves special mention. For the first time, a camera exists that lets you choose whether you want a low-pass filter in your optical chain or not. This is huge.

There's always been an uncomfortable trade-off in digital imaging between image detail and image artifacts; crank up the detail, and moiré patterns and color artifacts will follow right behind. Crank down the artifacts, and your images will appear soft and mushy as well. It's the job of the anti-aliasing filter (also called a low-pass filter or LPF) to manage this trade-off. Coosing just the right strength filter is a fine art, and greatly subject to personal preference.

Recently, there's been a move to do away with low-pass filters entirely, for the sake of the increased image sharpness you can get as a result. We at Imaging Resource believe this is a fundamental mistake, because once you have moiré patterns or color artifacts in an image, it can be difficult or impossible to get rid of them. While clever in-camera software can help reduce the incidence of such problems, it's mathematically impossible to do so in all instances. If you drop the low-pass filter, sooner or later, you're going to have moiré patterns or ugly color artifacts in your pictures.


In the past, the only way to choose how much low pass filtering you got -- or whether you got any at all --  was by choosing one camera over another. Some subjects need an LPF, while others don't, but you've had to make your choice one way or the other and then just live with it. At least, you've had to do so until now, thanks to Pentax.

Pentax's concept of mechanical anti-aliasing filtration is so revolutionary that we've devoted a large section of our just-posted Hands-On Preview of the Pentax K-3 to this one feature. Rather than repeat that all here, though, follow this link to access that section of the preview.

Will the other camera companies be able to respond to the challenge Pentax has laid down? Read our analysis to find out.