Quote:
Originally Posted by Astrofriend
Hi,
I made two new pages where I compare the stars from the Pentax lens and the Sigma lens. It's from center and the extreme corner. It's interesting to study these photos, in some cases the old Pentax non APO looks sharper then the more modern Sigma APO lens. And the Pentax is at full aperture (f/2.8) and the Sigma is stopped down to f/4.
Have a look at page 7 and 8:
http://www.astrofriend.eu/astronomy/...vs-pentax.html
What I know the Sigma APO 150 mm f/2.8 is very good, even for astrophotography when stopped down one step.
/Lars
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You can't compare one lens at F2.8 and the other at F4. All lens are better stopped down so the Sigma is made to look better. Even at F4 its showing a lot of coma. I prefer the Pentax. Its also showing star colour whereas the Sigma has all stars as white which of course they aren't.
The Pentax does show some chromatic aberration with those magenta rings around the brighter stars so you can either stop that down to F4 to help there or use the chromatic aberration slider in Lightroom to get rid of it.
Greg.