John, Pentax Norway graciously let me test the FA* 200 against the DA*200 earlier this spring. The DA sharpness is on par or better than the FA, and so is contrast.
I looked particularly for colour defects, and as far as I could see, the DA has a different approach to correction for different wavelengths. In the classic twig-against-bright-background situation that Fotozone whines about, I found the following (using K10D): The FA is less prone to the classic PF, BUT! The general optimization for colour aberrations in different in the two lenses. With the FA* they've tried a trade-off optimization, trying to bring all wavelengths *almost* into focus. With the DA*, they've corrected 100% for green, and let the red and blue wander off a bit. The result is that wherever you get other kinds of colour aberrations, it manifests in both green and purple with the FA, but only in purple with the DA. So the classic twigs will have alternating green and purple edges to them when shot with the FA, but only purple edges with the DA. The latter is far much easier to correct in post-processing. Also, it is worth noting that if you underexpose slightly, and then lift the shadows in post-processing, the DA looks far better. I think this is because most of the fringing for the colour purple is caused by the sensor anyway, and can be avoided by this technique. Further, it is also worth noting that the colour fringing happens at large apertures. Stop down to f/5.6 and it's all gone on both lenses. At f/4 it's already much better than f/2.8. I'd say the DA* is a step forward in lens design over the old FA*. Jostein 2008/5/20 John Mustarde <[EMAIL PROTECTED]>: > I'm curious - what is a "centering defect" > > Photozone shows a flaw in the DA* 200 - purple > fringing. Bad enough for me to avoid it. > "Unfortunately the DA* 200mm f/2.8 has quite a problem > regarding purple fringing. Purple fringing is a > blooming effect that occurs at extreme contrast > transitions. The camera sensor has surely a few stakes > in here but the effect is also dependent on the lens. " > . > -- > John Mustarde > Paris, TX > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. > -- http://www.alunfoto.no/galleri/ http://alunfoto.blogspot.com -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
