Mtmountainman wrote:
I don't know how the lens does it, but when I shoot at f2 I get nice sunstars when there are bright lights which I think adds a nice touch to the image.
I noticed that when I look into the back of some EF wide angle zooms (just checked the 24-70/2.8II and 16-35/4L IS), there is a secondary aperture that adjusts size as the lens is zoomed. It becomes smaller as the lens is zoomed wider; it's quite noticeable with the 16-35/4 that the secondary aperture changes size, less noticeable with the 24-70. This secondary aperture is very round compared to the lens's main aperture, but probably still not absolutely perfectly round. If this also exists in the 28-70, it could be a reason why you're seeing slight starbursts wide open. Or, when the aperture is wide open, the blades are still slightly in the light path, rather than fully retracted. IIRC this is the case with my Leica 90/2 Summicron-M APO ASPH.
Update: while editing images from the 24-70, the batch included one wide open at 24mm with a specular light source in the background with some starburst effects. It wasn't super clean and well defined rays, but more than I'd expect from a wide open aperture. I think it's possible that secondary aperture caused this.
TakesRandomPics wrote:
I see some weird outlines around the yellow flowers on the right is this a post-processing thing or just something that happens when shot wide open?
According to Flickr the photo was stopped down to F3.2, so not an issue shooting wide open. I am not really noticing any weird outlines on the yellow photos that look out of the norm.
