Sigma 17-70 compared to Sigma 18-50

Started Feb 15, 2006 | Discussions thread
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Miljenko Regular Member • Posts: 368
Sigma 17-70 compared to Sigma 18-50

In case you didn't notice, there was a new Sigma wide-to-mid range zoom offered recently. As it is not EX series lens, it's introduction went pretty silently as nobody expects much from this modestly priced glass. I had an opportunity to get one of the early samples for testing, and today results are more or less sorted and analized: http://www.pbase.com/miljenko/1850vs1770

Does it makes sense to compare two lenses positioned into different categories? According to results, it does! Check 100% crops extracted from full size pics shot with Nikon D200 at 19, 24, 28, 35 and 50 mm. At 19 mm Sigma 18-50 is set to 18mm mark, but actual focal length is 19mm. This time I did not publishing Imatest resolution charts. The reasons are poor edge results due to curved focal plane. Real life pics (like those presented in above crops) tell the story more realistic and accurate for those two lenses. Please check Excel charts where light fall-off and distortion was measured for both lenses: http://www.pbase.com/miljenko/image/56121391 http://www.pbase.com/miljenko/image/56121390

Besides pics and charts, here are brief findings: on average, lenses are roughly similar in sharpness. 18-50 excells at wide end, while 17-70 takes over at 35mm and above. 17-70 has slightly better contrast and is neutral in colour, compared to 18-50 that has slight yellow cast. For most comparisons 18-50 pics were trimmed by +0.3 f-stops, while 17-70 pics were lowered by -0.7 f-stops.

I'm leaving conclusions to you guys, but there's one thing I'll tell you: 17-70 sample I've tested stays with me for a few weeks more.
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Best regards, Miljenko
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