Change in Visible Noise after Changing Lens

Started Mar 19, 2008 | Discussions thread
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David G O Smith
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Change in Visible Noise after Changing Lens
Mar 19, 2008

I have a 20D. Until last week I used a Canon Ef-S 17-85 IS USM lens as my only lens. The visible noise I got at my usual ISO (400) and with my usual processing was fine.

I now have bought a Sigma 18-200 OS lens and find that with the same body and same processing the apparent noise is much worse. Nothing else has changed: same RAW processor, same other procedures.

It seems that at many focal lengths (35mm being a notable exception) the Sigma is sharper and has more contrast than the Canon, not to mention a different color reproduction.

When I look at the Sigma images after processing in dcraw 8.39 and without doing any sharpening that I have more detail than with the Canon lens using the same RAW processor.

Does it make sense that a sharper lens wlll, other things being equal, produce more apparent noise than a less sharp lens?

Any help would be much appreciated.

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