Lekker ReemRemy schreef op maandag 19 juni 2006 @ 08:29:
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Aannames, bah. Er zijn een aantal super- en hyperzooms die prima presteren. Geef die Bor de Wollef liever links naar foto's inc 100% crops gemaakt met super/hyperzooms, daar heeft hij echt meer aan
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Bron: http://www.photozone.de/8...igma_18200_3563/index.htm
Moet ik dezelfde soort quotes ook nog uit de Tamron 18-200 review van Klaus vissen of is het wel onderbouwd dat, in z'n algemeenheid, een hyperzoom een compromis is tussen optische kwaliteit en range? Ok, doen we ook nog even:An extreme 11x zoom lens like the Sigma has to come up with a complex optical design in order to deliver an acceptable quality - it is made of 15 elements in 13 groups including 2 SLD (Super Low Dispersion) and 2 hybrid aspherical elements.
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A major weakness of most long range zoom lenses is the level of distortions and the Sigma is no exception. At 18mm the lens produces a rather extreme degree of barrel distortions changing to pronounced pincushion distortions from 35mm and up.
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There's no such thing as a free lunch in lens land and the Sigma AF 18-200mm f/3.5-6.3 DC is no exception here. The resolution figures are generally quite decent and regarding the extreme zoom range you may accept the very pronounced distortions present throughout the zoom range as well as a few other shortcomings.
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So if you're interested in this lens it's a good idea to take your DSLR to your trusted photo dealer around the corner to check whether the camera's AF system is really up to the task. If so it is a good compromise between quality and zoom range.
Bron: http://www.photozone.de/8...mron_18200_3563/index.htm
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The Tamron shows a rather extreme degree of barrel distortions (3.6%) at 18mm which is only topped by the Canon EF 17-85mm IS so far. At 35mm and 80mm the situation changes to pronounced pincushion distortions decreasing to moderate pincushion distortions at 200mm. All-in-all no lens that you'd like to use for architecture photography.
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The vignetting characteristic of the Tamron is generally decent EXCEPT at 18mm @ wide-open aperture where the problem is very pronounced at 1.4EV. It's probably a good idea to avoid that setting (as we'll also see in the MTF chapter). From f/5.6 there's only a moderate to low degree of vignetting throughout the zoom range.
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In the MTF lab the Tamron delivered a relatively decent but certainly not flawless performance. The center portion is generally very sharp with excellent resolution figures at the wide end and still very good quality at 200mm. Unfortunately this isn't quite true for the borders at the extreme ends of the zoom range. At 18mm f/3.5 the border resolution is dismal but stopping down to f/5.6 lifts the quality to acceptable levels. A similar behaviour is observable at 200mm where the borders are quite soft at f/6.3. There's a slight increases in quality here towards medium aperture settings.
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Chromatic aberrations (color shadows at harsh contrast transitions) are very pronounced at the extreme ends of the zoom range peaking in an average width of 1.4 pixels at the image borders. Reducing CAs via tools (e.g. RSE Essentials or PS ACR) may be a good idea here. At 35mm and 80mm the issue is rather moderate.
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There's no such thing as a free lunch and the Tamron is no exception here. The extreme zoom range combined with the small lens dimensions comes at cost of some compromises. One is the rather slow max. aperture which limits the creative potential regarding shallow depth-of-field and the other compromise is, naturally, optical quality. In absolute terms the lens shows rather extreme distortions at the 18mm and vignetting as well as border quality don't impress either. The latter is also true for the 200mm setting. Nonetheless the lens is capable to deliver decent quality images under controlled conditions - reads: f/8 (see also the sample shots).
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ALL-CAPS WITH NO PUNCTUATION IS SO MUCH TRUER TO THE WAY THOUGHTS HURTLE OUT OF THE HUMAN BRAIN THAN CAREFULLY MANICURED AND PUNCTUATED SENTENCES COULD EVER BE