by Adam Wilt: Sony F5 / F55 Optical Low-Pass Filters

[Chris Hurd]

Originally Posted by Adam Wilt

OLPFs suppress high frequency detail that can cause aliasing and moiré, and most cameras have an OLPF carefully chosen to match the characteristics of their sensor’s native resolution (Nikon has a good writeup on OLPFs here). But when a sensor is scanned out in a non-native way, or at a different resolution, the OLPF’s characteristics may no longer be suitable: if it’s too strong, you’ll get an overly soft image; if it’s too weak, you’ll get excessive detail, aliasing, and moiré. For example, the Canon 5D Mk II’s OLPF is optimized for 21 Megapixel stills capture, but it’s woefully inadequate when that camera is used for 2 Megapixel HD capture. Folks like Mosaic Engineering make add-on OLPFs for the 5D Mk II and other cameras to better filter the image for HD capture, but these add-on filters add bulk and change the optical path length of the light behind the lens, so focusing marks shift.

Read the full article at Sony F5 / F55 Optical Low-Pass Filters at DV Info Net