LensRentals.com

Category Archives: Technical Discussions

A Data Processing Contest

Posted by

OK, when I introduced our new optical bench, I mentioned that it generates a lot of data. We gathered data for a nice comparison test (I mean who wouldn’t want to know how the Zeiss Otus and Sigma 50mm f/1.4 Art stack up against some nice Leica 50mm lenses). Since then I’ve spent about 20 [...]

A Look at Stopping Down

Posted by

  We all know that aberrations affect points of light off-center, making them blurred. We all know that some aberrations are worse the farther away from center we go. And we know that some aberrations are improved when we reduce the aperture. Some of us even know the various rules-of-thumb for what makes an aberration [...]

OLAF’s Lens Art

Posted by

This is a Geek Article, with very little practical information. But there are pretty pictures that non-Geeks might like. (Not the construction pictures, the ones further down.) First, I should explain why I haven’t posted much lately. Lensrentals was able to expand into some adjacent space, which was desperately needed. But the testing and repair [...]

The Sky is Falling and the Light is Leaking: the A7r Anti-Massacree

Posted by

Anti-Massacree - A humorous anti-war movement from the 1960s, suggested in the Arlo Guthrie song Alice’s Restaurant. The song, like many of my posts, was criticized for being overly long. Believe it or not, I’m mostly a lurker in online forums. I read the hysteria of the day mostly for my own amusement. Sometimes I type a [...]

A 24-105 Comparison

Posted by

Sigma has been releasing one great lens after another for a while now. Some, like the 35mm f/1.4 and 18-35mm f/1.8 zoom, have created feeding frenzies soon after (or even before) their release. Others, like the 24-105 f/4 OS, haven’t created a whole lot of fuss. So I thought we would do a little optical [...]

Examples Using an Optical Testing Station

Posted by

OK, I’ve done a couple of posts about critical focus for testing, and setting up an optical testing station.  This post will provide some demonstrations about actually using it. I’m going to use lenses that we optically adjusted back into proper alignment as examples. I’m doing this because it’s a great opportunity to show you [...]

Setting Up an Optical Testing Station

Posted by

There are a lot of right ways to do optical testing. The gold standard is to put the lens on a $150,000 optical bench or run it through a well-equipped Imatest lab. But unless you have an optical bench or Imatest lab handy, that’s not practical. We have to optically test around 400 lenses a [...]