I would love to do some more experimenting with star fields and stopping down, but weather has turned rainy so it will ave to wait. In the interest of this discussion however, I did put my 16/3.5 fisheye on the OM-D the other night and took one image at 60sec wide open, Here it is for a look. I did crank the ISO up to 1250 to try to get some more light thru this F/3.5 lens. I think it may belie the idea that fisheyes are more prone to this?
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So I found two more examples of same sky area which I took last year. Both are zooms and both seem better than the 75.
First (..0011) the 12-60 at about 42mm and wide open at F/3.8:
Second (..0086) is the 14-35 at 21mm stopped down 1 stop (dunno why I did that) to F/2.8:
I cropped em to show same FOV.
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So the skies finally cleard and I was able to test the 75/1.8 at other apertures. The purple fringing is defintely aperture dependent as the matrix photo shows. It's prominent at F/1.8, F/2 and is mostly gone by F/3.5
The last two show comparable-size crops at normal and using the in camera doubler.
Sorry, i was trying to add a 6 shot matrix to above post. I'll try again here:
But I keep getting this: The server returned an error during upload