I also have Samyang 85mm 1.4 and agree, like almost any very fast lens it's quite soft wide open but nice at f2 and very nice from f2.8 on. The main advantage of such fast lenses for me is not to use it wide open, but to get sharp images already at 2.8 or something.

Yeah, all of fast lenses have some character.
Guys, do you know history of this lenses?
As I know Canon 50mm FD is slightly price optimized FL 50mm.

Added fast lens comparison from Luminous-landscape article

See full version - Fast Lenses for the Epson R-D1

I like the Rokkor 50mm 1.4. The 58mm have a slightly better bokeh, but I prefer the color of the slightly Rokkor-X MD 50mm F1.4. And it was $45. That Canon 1.8 looks awful good.

I bought a "Mamiya/sekor AUTO 55mm f/1.4 M42 Screw Mount" on ebay last week and...eh.

It was damaged, a bent filter ring, so I got it cheap, $26 plus another $15 or so for the adapter, so I don't feel that ripped off, but if I had paid in the range of $100(where most f1.4 lenses start), I'd feel very gyp'd. That's a side by side still frame of a vid shot using the 75mb peak performance at MJPEG 1440x816 with the Sekor and a Minolta MC 1.7 55mm at iso 1600, both wide open, the dark at iso 100. The only light is the TV and a clip on work light with a 60 watt fluorescent. FPN wasn't that bad, and the grain looked like typical low light noise. Ironically, much less FPN in AVCHD vs the MJPEG

Can you tell wich is the Minolta MC 55m 1.7 and the Sekor 55mm 1.4? I forgot after recording it, :P so yeah, not much difference. I wouldn't spend more than $30 for the Mamiya /Sekor if I was you.

Just a thought. In my view, the value of "tack sharp" in video is highly overrated. Video is a moving image medium. As a consequence, "tack sharp" means very little; nothing I would suggest. A shot is often better if it's in focus (but not always). Even exposure is an esthetic decision not a practical one. To my eye, a "tack sharp" image can often detract from the theme of the image because the image quality, rather than its content, becomes paramount.

I have a 58mm MC Rokkor 1.2 that's razor sharp at 1.2 and built like a tank love it! Almost 3d in it's out of focus rendition. Also love the Hexanon 50 and 57 1.4 - great character. Edit oh and the lovely dinky Hexanon 40 1.8 !

@sdbest +1

With video, I've found that smooth edges blend together far more pleasingly than sharp, high-contrast edges. Probably everyone here has seen the distracting flicker effect produced when panning across a sunlit, highly-detailed scene loaded with crisp vertical edges. This is not a flaw in the camera, it is the inevitable result of high-contrast object movement projected at a low frame rate. It can be minimized by softening the image, either with long-shutter motion blur, or by shooting at wide-open apertures.

What I've found more important than sharpness is a lens' dynamic response to flare. Digital image sensors respond very differently to direct light sources than film does. The flat film plane responds equally well to light coming from any angle, whereas the photocells in an image sensor respond primarily to perpendicular, rather than oblique, light rays. This can produce harsh looking flare effects when a direct light source moves across a video frame.

Fast lenses typically use broad front lens elements to gather as much light as possible. Most vintage prime lenses predate modern aspherical lens designs that minimize flare. The problem with flare is that it's very difficult to measure or quantify in a way that can be used to predict how a lens will perform in practice.

I've tried out a fairly wide variety of prime and zoom lenses - Lumix, Zuiko digital, Leica, Canon FD, Nikon AIS, Konica Hexanon, Minolta MD, Tokina, Rokinon, and Sigma. I found the Lumix and Zuikos excellent for still photography, but they're often too sharp and clinical for video. Vintage primes look beautiful wide-open under controlled lighting, but flare is all over the map, especially when the front lens barrel is extended. What seems to work most consistently for my shooting style are prime and zoom lenses with internal focusing mechanisms that do not extend the front lens element. Their fixed, non-rotating front lens barrels also happen work well with polarizers, anamorphic adapters, and matte boxes.

I own Nokton and I think it is one of my best lenses. First and foremost because of the low light performance when no other glass can handle the darkness, I can do interviews which is a huge leap forward in the documentary world. I has to shoot secretly in a night club full of Russian thugs, this little thing worked (20mm 1.7 was too slow for that purpose). Prior to that we either had to use lights, or boost the video until we ruin it completely. With Nokton I don't even need a light source or if I use it, it can be a tiny consumer LED pointer - enough! I understand what you mean when you say you usually don't go lower than 1.4. "Too much shallow DOF will kill you", right? I think that it is just a matter of artistic choices. My most loved bokeh lens is Nikkor 50mm (120 $). My problem with it is that it's extremely hard to stabilize. But it's even more beautiful than Nokton. But Nokton is the best.

Bright lenses for the GH2 are not a problem. but WIDE ANGLE lenses are a problem. I tried all the c-mounts and other low price alternatives, but I start looking at the Olympus 12mm f2 and wondering if it is worth it.