Re: More Lense questions-Sorry-

Dave,

Jim is correct that a smaller Fstop such as F16 gives greater depth of field and therefore better chances of having focus through the entire depth of the photo. However, most zoom lenses has a sweet spot regarding sharpness of the entire frame (corner to coner top to bottom). Most zoom lenses sweet spot is somewhere in the range of F5.6 to F8. Above F8 they generally start to encounter greater and greater lens difraction. This causes the photo to be sharp in the middel and softer in the corners and perifery. You might got to http://www.dxomark.com/index.php]DXO Mark[/url] and see if they have tested the Tamron lense you have. If so, their review will show where the Fstop sweet spot is. Anyway, hope this helps unravel some of the sharpness mysteries about your lense.

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Tom Kneib
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