I may be the last person in the room to hear of this one, and I have yet to test it myself, but I thought I would pass it along for comment.
Igor's mention of purple fringing with the F 1.7x teleconverter got me Googling for "purple fringing" a and teleconverters. In some buyer reviews for a teleconverter that screws onto the FRONT of a lens, one person said that putting a UV filter between the teleconverter and the lens reduced purple fringing. That was the first time I had heard THAT. So I modified my search to "purple fringe" and UV and found that this apparently works with other (rear mounting) teleconverters as well. A few relevant links: http://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/54222-does-uv-filter-helps-cut-down-purple-fringing.html http://www.dpreview.com/forums/post/51786560 It seems to me that "purple fringing" can be caused by more than one phenomenon. If your blue channel is clipped you can solve the problem by purposely underexposing (to eliminate the clipping) and correct the exposure in post-processing. This thread http://photo.net/canon-eos-digital-camera-forum/00RJy5 gives some ways to tell if purple fringing is caused by axial aberration. I think it is worthwhile to pay attention to whether one is seeing the effect only when the lens is wide open. I realize that many people simply prefer to correct for this in post, but some might like to try a solution that prevents it in the first place, at least in some places. Darren -- Life is too short to put up with bad bokeh. -- 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.
