Thread: Pentax Lenses
View Single Post
  #5  
Old 05-10-2015, 04:45 PM
Retrograde's Avatar
Retrograde (Pete)
a.k.a. @AstroscapePete

Retrograde is offline
 
Join Date: Oct 2011
Location: Sydney
Posts: 1,727
Quote:
Originally Posted by gregbradley View Post
I wonder if you got a bad copy? Or alternatively I got a good one. I use mine with filtered imaging so perhaps that makes a difference but my copy is sharp wide open and no chromatic aberration or very little.
Hi Greg,

it's interesting that you and I have gotten such different results.
There could possibly be different revisions of the lens (I just grabbed one off ebay for around $200 so no idea what year it was manufactured or anything) or it could be the type of imaging as I'm still at the DSLR stage.

I'm very happy with the sharpness - it's just the CA that I've been having an issue with.

Quote:
Originally Posted by gregbradley View Post

I don't see chromatic aberration in those samples you linked. Those bright stars are blue which is correct. Either way blue fringing is pretty easy to correct in Lightroom so long as its not too bad.
It's not actually blue-fringes that I'm getting but rather purple/magenta-fringes on the medium-bright stars.
Here's a crop of a cluster near Eta Carina (single sub) that has not had any processing done to it to remove fringing. This is at f4.
Would certainly be interested in your thoughts on this.

Thanks,
Pete
Attached Thumbnails
Click for full-size image (EtaCAcrop.jpg)
160.7 KB27 views
Reply With Quote