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09-06-2015, 02:14 AM   #16
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Here is a link explaining coma - along with other types of distortion.Here is a couple of links that address lenses

09-06-2015, 02:18 AM   #17
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QuoteOriginally posted by Aaron28 Quote
fortunately for me (not that I know for a fact) setting infinity on my 14 is ok and its not at a hard stop suggested marking what is infinity on your 16 may prove very beneficial when it comes to shooting at night and should be a very capable lens at f2 with the astrotracer or not......
Yeah I don't think its set right... bit reticent to take it apart... still mulling over that

QuoteOriginally posted by FantasticMrFox Quote
But I wonder why everyone is having issues with focusing and trying to find infinity on their focusing ring? I simply use live view, find a bright star, then twist the focusing ring to the point where the star's diameter is smallest.
On pentax lenses, I simply spin it round, hard stop, bang I'm at infinity no messing about


The Sigma 10-20 stopped down seems very capable from what I've seem... and of course it covers very good FL to capture it all

I'm starting to think the Samyang only has the f-stop advantage over it... Samyang is not small

The DA 15mm is small enough to be used for lots of things, travel, daylight shots etc.

I would find the Samyang too big for travel
09-06-2015, 02:42 AM   #18
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I tried DA 15mm Ltd at f4 and coma of this lens at f4 makes it really not that good for stars (I didn't know about that when I took the photo). I had to crop pretty much half of the frame out due to this. Maybe at f5.6 it's better but then you need to increase ISO. I would have got better results using DA 35/2.4 - would have same field of view as cropped image from DA 15mm at lower ISO as this lens has very low coma even at 2.4.
I've seen some pretty impressive Milky Way shots on Flickr taken with Sigma 18-35/1.8 at f2 though.


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