Tag Archives: Photography

How to check a lens for decentering

There are many things that can be wrong with a photographic lens. Optics require tight manufacturing tolerances in order to produce high resolution images. Copy to copy variation is a serious issue, even (or especially?) nowadays. While most lenses leave the factory in good condition, a non-negligible percentage reaches the market with unacceptable optical flaws. One of the most common issues is decentering.
Since this happend to me a few times already, I decided to write a short article about it. I will first explain what decentering means and then continue with a simple procedure on how to test a lens.

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Equivalence: How to compare different camera systems

As you may know, to compare lenses of different camera systems in terms of angle of view, the focal length often needs to be converted to an equivalent value. What about aperture and depth of field or the expected amount of noise? Are those values also comparable and if so, how?

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