03-14-2011, 12:03 PM
[quote name='Brightcolours' timestamp='1300103084' post='6741']
Is it possible for you to try both lenses yourself?
People who have tried them side by side uniformly say that the Sigma is their favorite. A bit more contrasty, less CA wide open, and sharpness is not a let down for that Sigma.
About the AF noise, I know that for the Canon mount both lenses have motors inside the lens, and that there the Sigma is better (both noise wise and speed wise). And is more accurate. But I do not know if that is the same on Pentax... do they have their own motor for Pentax, or do they use the in-body motor (as I have always thought they are)?
If they use the in-body motor, I think the Sigma and Tamron will not show the difference you see for the Canon mount.
The Sigma is better built too, and it offers a closer MFD.
[/quote]
Thank you very much for your quick answer! Unfortunately I can not try both lenses side by side as the Sigma is officially discontinued and I have found only one shop in the Netherlands that still has the Sigma with the Pentax mount in stock. But they do not have the Pentax version of the Tamron lens, so I have to try that one somewhere else.
In my understanding both lenses are focussed by the in-camera motor of the Pentax K-5 via the slotted drive in the mount. However, there can still be a significant difference in the AF noise, as the mechanics in the lens (gears etc.) generate their own noise.
I have indeed read that the second version of the Sigma (the Macro version) has indeed good control of CA in contrast to the Tamron which has quite hefty CA at 17 mm. But what worries me is the border sharpness of the Sigma, I mean for portraits it would not matter that much, but shooting a scene indoors in low light might be a problem if I have to stop down to f5.6 to get decent borders.
Is it possible for you to try both lenses yourself?
People who have tried them side by side uniformly say that the Sigma is their favorite. A bit more contrasty, less CA wide open, and sharpness is not a let down for that Sigma.
About the AF noise, I know that for the Canon mount both lenses have motors inside the lens, and that there the Sigma is better (both noise wise and speed wise). And is more accurate. But I do not know if that is the same on Pentax... do they have their own motor for Pentax, or do they use the in-body motor (as I have always thought they are)?
If they use the in-body motor, I think the Sigma and Tamron will not show the difference you see for the Canon mount.
The Sigma is better built too, and it offers a closer MFD.
[/quote]
Thank you very much for your quick answer! Unfortunately I can not try both lenses side by side as the Sigma is officially discontinued and I have found only one shop in the Netherlands that still has the Sigma with the Pentax mount in stock. But they do not have the Pentax version of the Tamron lens, so I have to try that one somewhere else.
In my understanding both lenses are focussed by the in-camera motor of the Pentax K-5 via the slotted drive in the mount. However, there can still be a significant difference in the AF noise, as the mechanics in the lens (gears etc.) generate their own noise.
I have indeed read that the second version of the Sigma (the Macro version) has indeed good control of CA in contrast to the Tamron which has quite hefty CA at 17 mm. But what worries me is the border sharpness of the Sigma, I mean for portraits it would not matter that much, but shooting a scene indoors in low light might be a problem if I have to stop down to f5.6 to get decent borders.