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Advice please on the 24-70....
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<blockquote data-quote="WayneF" data-source="post: 492936" data-attributes="member: 12496"><p>No, I don't know much about lens testing, except a few basics how it is done. It has been done for more than 100 years, so a lot of experience is known, but it is still a very difficult problem to concoct meaningful numbers.</p><p></p><p>I may know a little more about digital sampling of that lens resolution. The big mistake we make is to imagine there is some one to one correspondence between pixels per mm and line pair per mm. There is Nyquists Minimum 2x sampling rule about aliasing (false detail due to insufficient sampling), but no maximum. More sampling is always better, at least within reason.</p><p></p><p>Measuring line pair per mm is difficult, determining when we can just make out that two fuzzy lines are distinguishable (not really the same criteria by which we judge our photos). Contrast of those fuzzy lines is a very big deal, so Modulation Transfer Function (MTF) is a big deal thought useful by lens manufacturers - but hard for many to understand, and again, not what we see in our photos. What we like to see is sharp photos, but measuring that in meaningful numbers is very difficult. We just know what we like. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p></p><p>Imatest manufactures printed test charts for others to use. Which seem very popular, and they do observe ISO standards (DxO makes up their own crap about megapixels). The Imatest chart is an ISO standard used by many tests - <a href="http://www.photozone.de" target="_blank">www.photozone.de</a> too, except they do not duplicate your links report about the Tamron at 70mm peaking at f/11. I trust Photozone more, they are not amateurs. The job sort of needs experienced people too. </p><p><a href="http://www.photozone.de/nikon_ff/789-tamron2470f28fx?start=1" target="_blank">Tamron AF 24-70mm f/2.8 SP Di USD VC (FX) - Review / Test Report - Analysis</a></p></blockquote><p></p>
[QUOTE="WayneF, post: 492936, member: 12496"] No, I don't know much about lens testing, except a few basics how it is done. It has been done for more than 100 years, so a lot of experience is known, but it is still a very difficult problem to concoct meaningful numbers. I may know a little more about digital sampling of that lens resolution. The big mistake we make is to imagine there is some one to one correspondence between pixels per mm and line pair per mm. There is Nyquists Minimum 2x sampling rule about aliasing (false detail due to insufficient sampling), but no maximum. More sampling is always better, at least within reason. Measuring line pair per mm is difficult, determining when we can just make out that two fuzzy lines are distinguishable (not really the same criteria by which we judge our photos). Contrast of those fuzzy lines is a very big deal, so Modulation Transfer Function (MTF) is a big deal thought useful by lens manufacturers - but hard for many to understand, and again, not what we see in our photos. What we like to see is sharp photos, but measuring that in meaningful numbers is very difficult. We just know what we like. :) Imatest manufactures printed test charts for others to use. Which seem very popular, and they do observe ISO standards (DxO makes up their own crap about megapixels). The Imatest chart is an ISO standard used by many tests - [URL="http://www.photozone.de"]www.photozone.de[/URL] too, except they do not duplicate your links report about the Tamron at 70mm peaking at f/11. I trust Photozone more, they are not amateurs. The job sort of needs experienced people too. [url=http://www.photozone.de/nikon_ff/789-tamron2470f28fx?start=1]Tamron AF 24-70mm f/2.8 SP Di USD VC (FX) - Review / Test Report - Analysis[/url] [/QUOTE]
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Advice please on the 24-70....
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