On Thursday 20 March 2014 08:41:56 Torsten Bronger wrote: > Hallöchen! > > Wolfgang Mader writes: > > May I please have your opinion on the reason of the green/blue rim > > around the flower [1]. The shot was taken with a prime lens, 50mm, > > into the general direction of the sun. > > It is longitudinal chromatic aberration, which is not easy to > correct. In particular, it cannot be corrected based on a profile > (e.g. Lensfun). Have a look at > http://www.photozone.de/images/8Reviews/lenses/canon_24_14_5d/loca_f14.jpg: > Everything behind focus has green fringing, and before it has purple > fringing. > > It can be removed by desaturating edges, limited to the area and > colours in question. > > Its root cause is low-quality glass. I suspect to used a close-up > filter. Such filters are usually only one single lens, so they > exhibit maximal chromatic aberration.
Well you are right about the chromatic aberration. Thank you. I read the dpreview of the lens [1] (Sigma 50mm F1.4 EX DG HSM) again, and they say "Perhaps more problematic, though, is the presence of quite strong bokeh chromatic aberration, which is magenta in front of the focus plane and green behind. This is most visible at wide apertures with their associated extremely narrow depth of field, and can result in a strong fringing artifacts in high contrast regions." The shot was taken wide open. I didn't use a close up filter. Would you consider this lens poor glass? In general, I am quite happy with it, but this chromatic aberration problem is a little disappointing. Best, Wolfgang [1] http://www.dpreview.com/lensreviews/sigma_50_1p4_c16 > > Tschö, > Torsten. ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. Written by three acclaimed leaders in the field, this first edition is now available. Download your free book today! http://p.sf.net/sfu/13534_NeoTech _______________________________________________ Darktable-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/darktable-users
