Originally posted by SteveinSLC Thanks all. Yeah, at distance, mine's not as sharp as I'd like at any aperture. If the 28-105 is a lot better, something is off. Maybe I could adjust it, but I'm not going to take the chance. Back it goes.
Now have to decide between another copy, trying the 24mm/1.4 instead(which also seems to have the same QC issues), or spending a lot more for the Pentax 15-30.
Looking for something fast and sharp for landscapes and astrophotography. Any thoughts one whether it's worth trying more Samyang/Rokinons, going with the Pentax or waiting for Pentax or Sigma to come out with something? There is also the Irix, but the couple of early reviews I've seen have had quality issues with that too.
Try another Samyang/Rokinon provided returns are easy. The 14/2.8 works well if you don't get a bad copy. Or, if you prefer the 24/1.4 field of view, try that one.
The 15-30 is a good lens too but much heavier than the Samyang primes.
---------- Post added 03-16-17 at 09:11 AM ----------
Originally posted by Meg4mi ...Do you think the problem here is focusing or the lense suffer from other issue ?
The 100% crop seems reasonably sharp.
Flickr says it was at 30 seconds, ISO 3200. 30 seconds: If the astrotracer was off or miscalibrated, stars move a little bit. ISO 3200: The noise is not bad but smears details a little bit.
It looks like the bright stars have an off-center halo. Was the 100% crop from the center or a corner?
Try a similar shot, at 15 seconds, ISO 800. The image will be much darker but might be easier to assess sharpness and aberrations. Compare the center and all 4 corners.