Category: Lenses and Optics
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Just The Lenses: Canon vs Nikon Zooms at 70mm
It’s impossible to accurately compare lenses from different mounts using any form of Computerized Target Analysis testing (methods like DxO or Imatest). Target analysis tests an entire system (camera and lens). People try to, of course, but it’s not accurate since you always have the added…
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Some M-Mount Field Curvatures
I haven’t posted very much lately. We’ve had some new equipment installed and we’ve been doing a LOT of testing as we develop our new database of lenses on the optical bench. As the database fills out I’ll be posting more than ever, just because a lot of this stuff is just fun. Today’s post is…
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Geeks Go Wild: Data Processing Contest Suggestions
A couple of years ago I gave a talk on the history of lens design at the Carnegie-Mellon Robotics Institute. The faculty members were kind enough to spend the day showing me some of their research on computer-enhanced imaging. I’m a fairly bright guy with a doctorate of my own, but I don’t mind…
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Sensor Stack Thickness: When Does It Matter?
The first post I made on sensor-stack thickness wallowed deeply in PhotoGeekery. This one is meant to be of practical use so I’ll try to leave the Geek stuff out. We’ll start with the simple facts. 1) There are several pieces of glass right in front of the sensor of every digital camera. 2) The…
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The Glass in the Path: Sensor Stacks and Adapted Lenses
_NOTE: This is a Geek Post. If you aren’t into geeky photo measurements, or into adapting lenses from one brand of camera to another, you’ll not be interested._ A year or two ago, I wrote a blog post where I basically showed lenses shot on adapters on other cameras aren’t acceptable for testing. If…
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Comparing Rangefinder and SLR 50mm Lenses. (Version 0.7)
Well before our Imagemaster optical bench was delivered, I knew what I wanted to do first: compare some Leica lenses with the best SLR lenses on a level playing. I did one comparison involving Leica lenses a long time ago, but Leica lenses are difficult to test in our Imatest lab. It’s nothing to…
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MTF – The English Translation
This post contains absolutely no mathematics. Explaining MTF without math is sort of like doing a high-wire act without a net. It’s dangerous, but for any number of reasons is more likely to keep the audience interested. ## Why Am I Doing This Again? I wrote an article on reading MTF charts several…
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A Look at Stopping Down
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…
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OLAF’s Lens Art
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…
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Roger’s New Toy Needs a Name
First and foremost, if you aren’t at least a little Geeky, this post is not for you. Unless you’re one of those people who thinks ‘just take some pictures, dammit’ when I write some article about resolution testing. In that case, you might like this article because we’re taking pictures to test…
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A 24-105 Comparison
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…
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Examples Using an Optical Testing Station
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…