đánh giá tamron 17-50 2.8

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Tamron AF 17-50milimet f/2.8 SP. XR Di II LD Aspherical (Canon) - reviews / Test Report
Lens Đánh Giá - Canon EOS (APS-C)



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Đánh Giá by Klaus Schroiff, published December 2007Special thanks khổng lồ Sitháng Procz for providing this lens!IntroductionThe Tamron AF 17-50mm f/2.8 SP.. XR Di II LD Aspherical (difficult lớn speak in one gasp ...)is the lachạy thử addition khổng lồ the popular mix of fast standard zooms. Tamron has categorizedthe 17-50mm as SP (Super Performance) lens - Tamron"s professional grade product league.As indicated by the Di II the lens provides a reduced image circle so it is onlycompatible to lớn APS-C DSLR. Its field-of-view is equivalent to~27-80mm (1.6x crop) on full frame cameras. The lens is available in Canon, Nikon and Sony(KM) mount. At a price around 400€/US$ the Tamron costs only a fraction of the genuinemanufacturer alternatives making it pretty attractive to budget shoppers who are looking fora good khuyến mãi for their bucks.
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The optical construction is made of 16 elements in 13 groups including two hybrid aspherical elements,one LD (Low Dispersion) glass element and one XR (Extra Refractive) element.According khổng lồ Tamron the characteristic of the XR element allows a very compact thiết kế (82x74milimet, 434g).Both the Canon EF-S 17-55milimet f/2.8 USM IS and even more so the Nikkor AF-S 17-55milimet f/2.8 ED aresubstantially bigger but the Sigma AF 18-50mm f/2.8 EX DC is pretty much comparable in kích cỡ.The min. focus distance is 0.27m resulting is a max. object magnification of ~1:4.5 at 50mm.The lens features 7 circular aperture blades. The filter size is 67mm.
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The build quality is very decent build qualitybut typical for most Tamron lenses there"s a little too much plastic in there for my taste.Nonetheless it is still one of the better implementations in Tamron land. The zoom ring feelsvery smooth. Same goes for the focus ring which is even a little damped (are the old times comingbachồng after all ?). On the downside Tamron still didn"t manage khổng lồ decouple the focus ring from theAF motor so the ring rotates during AF operations. As you can see in the product shot above sầu the lens extends when zooming towards the longkết thúc of the zoom range & the supplied petal-shaped hood adds a little extra length on top.Thanks to lớn internal focusing the front element does not rotate so using a polarizer remainseasily possible.Due khổng lồ a very short focus path (about 45 degrees) the slightly noisy AF is very fast.During the field tests the AF accuracy was fine in outdoor conditions but a little unsure indoors(low light) at the wide-kết thúc of the zoom range - the EOS 350D is no stellar performer here anyway though.

Chuyên mục: Kiến thức