Originally posted by MossyRocks Not that I can tell even when running it wide open but there is a little bit of star bloat wide open. Also wide open there is some coma in the corners even on APS-C but it is minor. Shortly after getting the lens I gave it a fairly comprehensive test and found that it basically becomes perfect when running at f/3.5. The coma is gone and the stars get to their smallest size at this point. Also it really needs a filter in the filter holder without it performance drops noticeably for astro. I tested it with no filter, a hoya red intensifier (poor mans light pollution filter), and the top of the line ProMaster UV multi-coated filter.
Another thing I found was that using the 1.4X-L rear converter seems to make the lens better. Using it with that converter I can run wide open (f/4) and can't find even the minor issues I saw with just the lens wide open. I did stop it down out to f/8 and the only difference I found was that got more noise after equalizing the brightness of the test shots.
I got one of those red intensifiers a while back too, along with a light red B+W that has made me a fan of that company. I'm not sure which one I like better, though the B+w really drives off the blue end of lp and is a lovely little brass tank, the Hoya just looks awesome when applied to landscape shots, especially around sunset - which I think was it's original claim to fame. It hasn't hurt my stationary and gps night shots either.
I've never hd any luck with my tc's but then they're super cheap knock offs I got with other lenses and stuff. I will confess to buying that horrid 3x cpc though.
Just to pretend to stay on topic, I bought a scrap fast 50 pentax-m 50mm/f1.4 for 30$ on a complete gamble last year and I'm calling it
"Zombie", actually I think I'll call it Tae chan after my favorite zombieland saga character. :P
I thought the gamble was a total loss after cleaning revealed what appeared to be balsam separation in the rear group. I tried a couple of the usual tricks to see if I could get the lenses apart to clean them but nothing worked, including the somewhat terrifying boiling water soak, which was the last resort before I put it back together still a bit hazy, took a few lackluster test shots to compare my work and stuffed it in a lens can in the extras box. I guess I just needed to wait a while because I got it out recently and found it clear as a bell! --and yep... those things are cool! Even though the sensor crop makes the fov look a bit long on my aps-c k50, you can dial dof to nearly nothing and make almost(not a selfie guy) any portrait look amazing.