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Category Archives: Lenses and Optics

A Look at Stopping Down

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  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

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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 [...]

A 24-105 Comparison

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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

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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

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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 [...]

Why You Can’t Optically Test Your Lens with Autofocus

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By far the most common email and PM I get basically says, “I think my lens is optically out of sorts. What do you think?” The second most common is, “So what’s the best way to optically test my lens without a ton of equipment.” Years ago I wrote an overly long post about testing [...]

Tamron 150-600 Telezoom Shootout

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There’s been a lot of interest in the newly released Tamron 150-600mm f/5-6.3 SP Di VC USD lens. (For those wondering what the initials mean, VC means vibration compensation, the others all read ‘marketing drivel’.) But meaningless initials or not, with a price under $1,100, a superior range, and vibration compensation, this lens has created a lot [...]