07-14-2010, 02:51 PM
This lens is quite interesting in the trade offs that were made. Basically is serves the purpose, which is to deliver high sharpness over the field of view at a cheap price, so it's a winner.
IMHO a few things make this low price and high performance possible, by allowing a relatively simple overall design:
- No electronics, no AF, no coupling... who cares? It's a wide angle for landscapes!
- Plenty of uncorrected distortion. Again, for most natural landscapes who cares?
- Small aperture far from the center (high vignetting)[sup]*[/sup].
[sup]*[/sup]This is also why some large format lenses perform so well off their centers: they have a very small aperture. The diaphragm is effectively stopping the light pencils which would be distorted otherwise, resulting in very high vignetting. This is probably why the lens performs well wide open in the corners in terms of sharpness because of vignetting, not despite it <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt=':o' />
IMHO a few things make this low price and high performance possible, by allowing a relatively simple overall design:
- No electronics, no AF, no coupling... who cares? It's a wide angle for landscapes!
- Plenty of uncorrected distortion. Again, for most natural landscapes who cares?
- Small aperture far from the center (high vignetting)[sup]*[/sup].
[sup]*[/sup]This is also why some large format lenses perform so well off their centers: they have a very small aperture. The diaphragm is effectively stopping the light pencils which would be distorted otherwise, resulting in very high vignetting. This is probably why the lens performs well wide open in the corners in terms of sharpness because of vignetting, not despite it <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt=':o' />