06-14-2010, 01:23 PM
[quote name='vc13130' date='14 June 2010 - 01:34 PM' timestamp='1276518897' post='494']
someone did a "bokeh test" where they manually set the focus to 1 m and looked at the bokeh of background lights at f 2.2, 2.8, 4.0, etc. and showed that it was the same between 2.2 and 2.8 but different between 2.8 and 4.0.[/quote]
Well, at 1m that's hardly surprising, since wide open isn't reported as f/2.0 anymore (probably f/2.2 instead) and consequently f/2.8 isn't a full stop away. If this is how the test was performed, than it was doomed to fail because of a faulty setup.
And in addition it tells nothing about a possible misalignment of the aperture lever. Nonetheless I will check this theory tonight (I have my doubts, though).
Not to say the Tamron doesn't have a problem wide open ... it certainly does. But my feeling is more that some people posting "test results" are completely unfamiliar with the effective aperture reported by macro lenses with F mount.
Finally: our MTF measurements are done at a larger distance, 60 times the focal length, so 3.6m in this case.
-- Markus
someone did a "bokeh test" where they manually set the focus to 1 m and looked at the bokeh of background lights at f 2.2, 2.8, 4.0, etc. and showed that it was the same between 2.2 and 2.8 but different between 2.8 and 4.0.[/quote]
Well, at 1m that's hardly surprising, since wide open isn't reported as f/2.0 anymore (probably f/2.2 instead) and consequently f/2.8 isn't a full stop away. If this is how the test was performed, than it was doomed to fail because of a faulty setup.
And in addition it tells nothing about a possible misalignment of the aperture lever. Nonetheless I will check this theory tonight (I have my doubts, though).
Not to say the Tamron doesn't have a problem wide open ... it certainly does. But my feeling is more that some people posting "test results" are completely unfamiliar with the effective aperture reported by macro lenses with F mount.
Finally: our MTF measurements are done at a larger distance, 60 times the focal length, so 3.6m in this case.
-- Markus
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