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Does wider zoom range mean lower image quality?
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<blockquote data-quote="lokatz" data-source="post: 644269" data-attributes="member: 43924"><p>Good and valid questions, thank you. Every so often, the magazine publishes a report on exactly how it tests. I don’t have a copy of the last issue where they did that, and quite honestly, I wouldn’t want to have to translate all of that into English anyway, but it did make sense to me. In a nutshell, they measure, always across the whole aperture range, resolution, distortion, vignetting, and chromatic aberration, each at the short end, in the middle, and at the long end. They then use a single formula to translate those measurements into one percentage score, where 100% represents a fictional “ideal” and loss-free optical transmission.</p><p></p><p>If we looked at the formula in detail, I’m sure some of us would argue that sharpness should get more (or less) weight, distortion should get more (or less) weight, etc., but I doubt any of that would make huge differences in the relative comparison between different lenses. You asked for how visible these differences are at 1:1, which is the very same question I would ask.</p><p></p><p>Well, the mag also publishes shots, always of the same subject, always at a distance such that it fills the frame, always showing 1:1 cutouts from the center, from the edge, and from a corner. There are always two shots, one taken at the largest aperture the lens offers, the other stepped down to half of that aperture. Taken together, these images give a visual idea of how much sharpness, vignetting and CA each lens has. This test procedure makes a lot of sense to me – I hope to you, too. </p><p></p><p>Here are three examples from the lower end of the lens performance spectrum to illustrate what these IQ score differences mean in practice. The compilation from different tests was done by me; I also added the explanatory text. I picked the Tamron 16-300 (average IQ score: 43.5), Nikon 18-140 (51.8) and Nikon 18-105 (59.2). It is pretty obvious to me why they see the lenses at different IQ levels, so the lens scores match the visual check these shots allow, which I find crucial and further raises my confidence in their testing. </p><p></p><p></p><p>[ATTACH]271086[/ATTACH]</p><p></p><p></p><p>I couldn’t agree more that any kind of ranking is suspicious as long as the criteria used aren’t clear. I think they are clear enough here, so I stand by my initial post in this thread.</p></blockquote><p></p>
[QUOTE="lokatz, post: 644269, member: 43924"] Good and valid questions, thank you. Every so often, the magazine publishes a report on exactly how it tests. I don’t have a copy of the last issue where they did that, and quite honestly, I wouldn’t want to have to translate all of that into English anyway, but it did make sense to me. In a nutshell, they measure, always across the whole aperture range, resolution, distortion, vignetting, and chromatic aberration, each at the short end, in the middle, and at the long end. They then use a single formula to translate those measurements into one percentage score, where 100% represents a fictional “ideal” and loss-free optical transmission. If we looked at the formula in detail, I’m sure some of us would argue that sharpness should get more (or less) weight, distortion should get more (or less) weight, etc., but I doubt any of that would make huge differences in the relative comparison between different lenses. You asked for how visible these differences are at 1:1, which is the very same question I would ask. Well, the mag also publishes shots, always of the same subject, always at a distance such that it fills the frame, always showing 1:1 cutouts from the center, from the edge, and from a corner. There are always two shots, one taken at the largest aperture the lens offers, the other stepped down to half of that aperture. Taken together, these images give a visual idea of how much sharpness, vignetting and CA each lens has. This test procedure makes a lot of sense to me – I hope to you, too. Here are three examples from the lower end of the lens performance spectrum to illustrate what these IQ score differences mean in practice. The compilation from different tests was done by me; I also added the explanatory text. I picked the Tamron 16-300 (average IQ score: 43.5), Nikon 18-140 (51.8) and Nikon 18-105 (59.2). It is pretty obvious to me why they see the lenses at different IQ levels, so the lens scores match the visual check these shots allow, which I find crucial and further raises my confidence in their testing. [ATTACH=CONFIG]271086._xfImport[/ATTACH] I couldn’t agree more that any kind of ranking is suspicious as long as the criteria used aren’t clear. I think they are clear enough here, so I stand by my initial post in this thread. [/QUOTE]
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