One of my first post was about using 135mm legacy lenses on mirrorless systems. Since then I've acquired another 135mm lens but not one that can be adapted to all systems. The original post was about legacy lenses easily adapted to modern digital mirrorless systems via a cheap dumb adapter.
This new lens has an FE Sony mount as the Sony native lens selection is rather lacking. I have some A mount lenses but you need an adapter for those too. The native Sony lenses that have just been released are really pricey I find and since the Sony cameras are only one system that I like to use I tend to save where I can for more important purchases (such as the Olympus 25 f1.2).
The lens is a Samyang 135mm f2 lens. I must admit, I do own a few of the manual focus lenses from Samyang for the simple reason they have excellent build quality, are sharp and are exceedingly good value for the price. One drawback is they do tend to be on the heavy side. (Kirk Tuck is a fan of some of the Samyang lenses. Take a look at his site here). Some wouldn't buy them because they're manual focus only but that doesn't really bother me. Maybe the one drawback I can really think of is size and weight. I must warn you, the 135mm is large and it is quite heavy on the front of the Sony A7x series of cameras, but manageable.
I normally like to use the older, smaller 135mm lenses on the Sony A7r because I was, and still am, impressed by the image quality that sensor gives me. Although it's been superceeded by the A7rII, I have at this point no intention of upgrading. Yes, the A7r has it's quirks (slow and the shutter sound is horribly loud) I don't use it indoors where the shutter sound could become a problem. I'm mostly outdoors so it doesn't really bother anyone. Put it this way, nobody has come up to me and complained that my camera is too loud 
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Specs:
Weight: 830g
Size: 122mm x 82mm
F: 2 - 22
MFD: 0.8m
Filter: 77mm
If you want a comparison just take the Canon 100m f2.8 Macro lens. The Samyang might be a touch fatter but nothing to write home about. Focusing on the Sony A7x series cameras with the focus peaking they offer is nice and quite accurate. The lens is sharp from f2 and sharpens up slightly when stopping down. My main concern here was sharpness at f2 where I intend to use it mostly. There is slight vignetting on the Sony bodies but that can easily be removed in PP. Apart from that I can't fault it at all. This dwarfs my old legacy lenses though by a large margin not to mention the weight so it might cause me some space problems later on.
The lens can bought in nearly all mount formats and would be equal to a 270mm on the M43 bodies and just over 200mm on APS-C sensors. Of course one advantage of buying in the E mount is that I can use the lens on my Sony APS-C and FF bodies. The Sony APS-C bodies I have are due for an update pretty soon as there's been a big functionality jump in the new bodies. More on that later in another post. Using this lens on a Sony APS-C camera would be like using a lens with a camera mounted on it. There could well be a balance problem with these bodies (especially the Nex-5N which I like using), Could be it won't be workable but I'll certainly try it out.
Following are some images taken on the Sony FF bodies. I'll follow this post (or update it) as I experiment further. I can really recommend these lenses if you haven't tried them. Even rent one for a day or so to get the feel. I'm certain you won't be disappointed with the image quality.
All of the following images were taken on the A7II because I knew I was going for walk in the forest and the light isn't great so image stabilization would come in handy, otherwide I would have used my A7r.
The image above and the following two I made within seconds of each other.
Three slightly different poses and I just couldn't decide which one to post, so I posted them all.
All look good in my opinion.
