But first things first. Since the last time I have seriously upgraded my camera. I went from a Sony NEX5n which I still love to the 24MP Sony A7 so the quality of the photos should be much improved. I will try to post a complex review of the camera in the near future, but I will just say it's an amazing piece of gear and it surpassed my expectations in every aspect.
The Samyang 135mm is quite a bulky lens, but achieving such wide aperture at that focal length just takes its toll and there's no way those laws of physics can be bypassed. The first thing you notice are just huge front and rear optical elements, which are a promise of good optical quality and the first photos you take just confirm that 100%. If I could summarize the experience in just one sentence, it would be: "that is the sharpest lens I have ever used". I have seen a couple tests online prior to using it, but taking the photos myself and then seeing them on a large screen I just couldn't believe my eyes.
Some of my samples, all taken at f/2 because stopping down is not necessary here (and several 100% pixel per pixel crops):
But the sharpness is not all. This lens has got amazing colour rendition and contrast...
....and spectacular bokeh...
Every one of 24 million pixels is put to use by this lens. You can see on some of the crops that the detail is almost finer than the digital 'grain', I would love to see some samples from a Sony A7R or Nikon D600. I have not corrected chromatic aberration on any of the photos.
Using this lens I camer to had to remember to keep my exposure times short (as it is a tele lens) which was more than easy during the day, but in the afternoon I had too boost ISO100 to ISO800 to stay in the safe zone.
There is an old rule of thumb for exposure times. When handholding your shots your times shouldn't be longer than 1/(focal length), so basically for this lens the value was 1/135s and 1/160s when you round it off to an existing value. You have to remember though that this applies to full frame, when using a crop sensor, you need to calculate the equivalent. So when using Sony NEX5n (crop factor of 1.5x) with this lens the safe exposure time would be around 1/200s as 1.5 times 135 equals 202.5. You have to remember that this rule just tells you what is the longest eposure time you can safely handhold, it does not mean that all of those shots will be sharp. Shaky hands can ruin everything, but if you are steady, you can just as well pull off a longer exposure time. But still I think this is very useful to keep that in mind.
* The lens I tested was a Nikon mount and I used an adapter to mount it. This does not change anything, but I thought some people might wanna know that.
edit 19.04.15 - I'm adding some more samples: