Category: Technical Discussions
-
Cine Lens Teardown Comparison: Zeiss 85mm CP.2 T2.1 and Rokinon Xeen 85mm T1.5
I was pretty excited when I first heard about the Rokinon Xeen line of Cinema lenses. For several years now, Samyang / Rokinon photography lenses have given photographers with reasonable expectations some superb alternatives. They sell optically excellent lenses at amazingly low prices. There are…
-
MTF and Variation: An Example
We’ve spent most of the last month establishing a database of MTF curves and expected copy-to-copy variation for a number of lenses. Most people have a general idea about what we’re doing, can follow along the basics of MTF curves, etc. But many other people also have a very good question, “How…
-
Quick MTF of the Tokina 24-70 f/2.8 PRO Fx
* Courtesy Tokina, USA * Tokina is releasing a new competitor in the 24-70mm f/2.8 standard zoom lens group. It’s a reasonably sized lens, having an 82mm diameter front ring, measuring 4.25 inches long, and weighing 2.2 pounds. That’s just a bit smaller and lighter than the Tamron 24-70mm f/2.8 VC…
-
A Quick Look at the New Sigma 24-35 f/2 Art
* Image Courtesy Sigma USA * I generally do MTF testing on multiple copies of a given lens so that I can present the averages, look at sample variation, and stuff like that. I’m always aware that looking at any single copy of a lens, especially a zoom lens, gives only a limited prediction of how…
-
Variation Measurement for 50mm SLR Lenses
Last week we posted an introductory article on how we measure copy-to-copy variation in different lenses. I’ll be continuing to publish these results over the next few weeks for prime lenses. We will eventually have a database put up, but I think it’s important to look at the different lenses in…
-
Measuring Lens Variance
Warning: This is a Geek Level 3 article. If you aren’t into that kind of thing, go take some pictures. I’ve been writing and discussing the copy-to-copy variation that inevitably occurs in lenses since 2008. (1,2,3,4) Many people don’t want to hear about it. Manufacturers don’t want to acknowledge…
-
I Don’t Know Why It Swallowed a Fly – Weather Sealed Lens With a Fly Inside
I’ve been blogging about testing and taking apart camera equipment for almost a decade. Lensrentals.com has many thousand lenses these days, and they all get used frequently. When you have lots of lenses and they get used frequently, stuff gets inside them. Usually the stuff that gets inside is…
-
A Thinner Sensor Stack
A few months ago, before my hiatus from blogging, we did a series of articles showing the effect that a thick sensor stack (the glass above the sensor) had when we use adapted lenses designed for a thin sensor stack. The first one was mostly about theory, the second about when it was likely to…
-
A Data Processing Contest
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 hours…
-
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…
-
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…
-
Setting Up an Optical Testing Station
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 day,…