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Lens Testing ProtocolsAre Lens Reviews worth bothering about..

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Posted by novicius: Thu Feb 4th, 2021 23:59

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I came across a website called PhilipReeve.net,....more precisely an interview with the lens designer of the LAOWA 15MM 2.0 ZERO-D FE , a Mr.DAYONG LI.

It is a Rangefinder / Mirrorless lens, as I found the Interesting part of said interview the comments of Mr.DAYONG LI about the Lens testing procedures of reviewers , here is a link to the Interview :

https://phillipreeve.net/blog/the-man-behind-the-lens-mr-li-laowa-15mm-2-0-zero-d-fe/

I have posted the link out of respect and Courtesey , hoping it is accepted here as well,..however, here is the exerpt that I found Interesting and I Quote :

Quote : \" PR: There are now several websites conducting more or less sophisticated measurements of lenses and then coming up with a rating of some sort. Personally I think those tests rarely reflect the actual quality of a lens and are often performed at too short distances. Still, many people use these ratings and tests to base their buying decisions on. Do you have a look at the tests of your lenses and are those tests something you already think about when designing a lens?

Mr. Li: Yes, a lot of reviewers are testing lenses in the laboratory. But the equipment and methods they are using are generally protocols designed for the evaluation of older, less demanding optics. However, many modern lenses now being produced feature much wider angles of view and much higher resolution. By using those older protocols, tests make them seem to have much poorer performance than they really do. This is because these lenses are designed for best performance at the most common shooting distances. For instance, with wide angle lenses, we would concentrate on infinity for landscape pictures, and distances of at least several metres for architecture. Therefore, we have to ensure a good performance from at least 1m distance and out to infinity. Since the angle of view is very large, at subject distance shorter than 1m, we will get extremely high field curvature. Thus the edge performance will drop significantly if the lens is focussed centrally at these short distances. The problem arises in laboratory tests when a chart is used to test resolution. With a wide angle lens, in order to capture an image of the whole chart, the shooting distance must be very short. Maybe it is just 60-80cm away from the lens. Most ultra-wide angle lenses have their worst performance within this distance. But in fact it is uncommon to take shots this close in real life while using an ultra-wide angle lens. So if we test the performance of a lens using these protocols, the result will be very inaccurate. I have seen some websites showing some bad test results for an ultra-wide angle lens, but giving sample landscape and architecture photos taken with the lens which are excellent. I think this explains why these tests can be so inaccurate.\" - end Quote.

We have here debated before , the Validity of Lens testing by Independent reviewers and therefor I thought it worth to note the views of a Reputable optical Engineer , also, I found the Entire Article worth a read , hoping that I have Not committed any Violations of copyright , hence my posting the link to the entire interview.

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