| Latest Review Posted | Sigma EX Aspherical DG DF RF 20mm F1.8
By this point, it's pretty clear that there is a great deal of sample variation within this lens. I would only recommend purchasing a copy if you can test it before buying or if the seller can provide sample photos. With that being said, here's my 2˘ on the copy that I own:
Optical Qualities:
•Wide open, this lens isn't anything to write home about. It's a tad soft even in the centre. Bokeh highlights have visible 'soap bubble' bokeh balls. There is noticeable purple CA in high contrast areas. Vignetting is obvious.
•At f/2, which is one 'click' down (~1/3 of a stop), the lens smartens up to have very good sharpness in the centre and the bokeh mellows out somewhat. CA is reduced. Vignetting is still obvious. The lens' IQ is entirely useable at this point.
https://www.pentaxforums.com/forums/members/43506-gerbermiester/albums/14186-sigma-20mm-f1-8-ex-aspherical-dg-df-rf/picture137198.jpg
Chip @ f/2
•At 2.8 through f/8, the lens is a great performer. Sharpness continues to improve and becomes more uniform across the plane of focus. Bokeh smooths out to pleasing levels. CA is negligible (except in the extreme corners), Vignetting is reduced to the point of not being a concern.
https://www.pentaxforums.com/forums/members/43506-gerbermiester/albums/14186-sigma-20mm-f1-8-ex-aspherical-dg-df-rf/picture137200.jpg
Chip @ f/3.5
•A great feature of this lens is its ability to make pleasant sun-stars when stopped down accordingly.
•Veiling flare is well control... |
