Unsure of this lens' optical quality


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Oct 16, 2010
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My Rokinon 85mm f/1.4 has recently arrived, and I'm unsure of the optical quality of this new lens. Could it be a dud?
It's my first lens with a wide aperture and I don't know if it performs as well as it should. I took some test shots on a tripod; there is some quite noticeable spherochromatism at wider apertures and it seems to lack sharpness.
Here's the test images (click the thumbnails to see at 100%):

f/1.4, f/2.8, f/4.0, f/5.6

I've read that the lens is supposed to be very sharp even at f/1.4.
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It's a little soft wide open, but that's to be expected... No lens is at it's best wide open.

Of these samples, 5.6 looks best to me, but again - that's sort of what is expected...

edit, again...
Did you do test shots beyond 5.6? It might be interesting to see where the sharpness starts to fall off.
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That's true, but I've read that the lens is supposed to be sharp at f/1.4 nonetheless. I'm trying to find similar test images; maybe photographing a magazine is unfair. Yellow bars appear on the image or I am unable to get the image in focus when trying to photograph a computer monitor at f/1.4 if that's relevant to its optical quality (but it's an LCD screen).

EDIT: The images appear cleaner (and sharper) when photographing subjects that are further away.

I'm not really concerned with small apertures (I got this lens for background blur and low light capabilities after all), so I haven't taken any test shots with smaller apertures than f/5.6.
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Well, I would certainly say that it is "sharp" at 1.4, but not "sharpest".

The closest I have to that lens is a Canon 85mm 1.8, and I don't think I have any shots from it that would make a worthwhile comparison for this thread...

Can you elaborate a little on the 'yellow bars' comment? I'm not really sure what you mean there... Is it chromatic aberration? ...Or something else?
Here's a quick shot of my monitor, perfectly in focus, at 1.4:
(click to enlarge)
The yellow bar is at the bottom, but it can be elsewhere.
At the two widest apertures, longitudinal chromatic aberration is pretty clear: that is the sort of magenta-colored fringing around the out of focus type in the foreground, and the BLACK type at the focus plain, and then green-fringed out of focus type behind the focus plane. This is pretty normal for a high-speed 85mm: Canon's 85/1.2-L has it really bad; Nikon's 85 1.4 AF-D has it too ; your lens has it--in fact, MANY telephoto lenses have this issue at their widest two or three stops. By f/4 the effect is much,much harder to see. These photos are just ONE test sequence...but I'd say the lens looks okay...why not shoot it on some actual "subjects" tomorrow or this weekend and see how it does??? Unless you happen to shoot a lot of books and magazines indoors under incandescent light, these test shots do not give you any "real" indication of how this lens performs for normal use.
The yellow bar is likely somehow related to the refresh rate of your monitor (especially if it moves). And the 'softness' towards the top of the frame is mostly likely because the sensor plane was not perfectly parallel to the monitor.
Thanks. I'll test the lens outdoors tomorrow or when I have time. I suppose these shots may make the lens appear bad; I won't be photographing this kind of stuff with it anyways.

EDIT: Also, do fast primes with shorter focal lengths have these issues too? (Such as 35mm and 50mm.)
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Thanks. I'll test the lens outdoors tomorrow or when I have time. I suppose these shots may make the lens appear bad; I won't be photographing this kind of stuff with it anyways.

Some bigshot photographer used to say the only way to know show good a lens was was to "live with it for a year". For example, right NOW, in much of North America, the weather is crappy, and there's little sunshine; if a lens tends to have somewhat low contrast, then it will look bad this time of year; in bright, blue-sky weather though, it'll look much better. In the winter, a lens might have to be used at f/2 to f/4 due to low light; the lens very well might offer PEAK performance at f/5.6 or f/6.3...but in the winter, you'd never get to that f/stop under most conditions. In the summer, there are AMPLE chances to shoot directly toward bright, strong sunlight...in the winter, not so much--and so how a lens shoots contre joure, or "against the light", is sort of an unknown quantity...so...yeah...you get the idea...

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