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08-06-2016, 09:53 PM   #1
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Difficulty with Rokinon 14mm f2.8 on K-1

Hey guys, been a while since I posted. I'm going to post some recent stuff in the K-1 Pictures thread this weekend.

Anyhow, I recently picked up a second hand but unused Rokinon 14mm f2.8 from a classified ads site and got to finally spend some time with it today to test it properly in the environment I intend on using it (nature, landscapes, etc.)
After reading many many reviews and looking at hundreds of sample images, including many created with the K-1, I can't say I'm thrilled following my experience shooting with it.

The first thing that bothers me, other than the fact that I can't say that anyof the images produced with it are what i would consider 'very sharp', is the terrible time I'm having focusing with it.
I'm using the Live View most of the time and it's setup on a tripod to ensure the best possible performance (also using 2 second timer almost exclusively) and, whenever in Live View, the image i see on the display is blurred but almost to the point where the highlights are creating a Halo effect making it very very hard to focus. It seriously looks like there's clear jelly crap smeared on my lens when i'm trying to focus (at a few X multiplication, other lenses don't do this) The end result doesn't show this, but again it's never as sharp as I'd like it. I don't think this is related to the focus peaking feature because I've played with this and don't believe it affected this issue...

I've also found mentions online of many people with this lens making adjustments to the focus rings themselves using the 3 screws under the rubber ring, but that's only to set a new Infinity point... I don't even look at my markings when I'm shooting so I don't think that fix would affect me either.

Any ideas? Could this be related to some setting somewhere or did I just buy a 350$ potato? I'll provide some samples in the morning! Thanks in advance!

08-06-2016, 11:13 PM   #2
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Sounds like there might be something wrong with this lens. This lens is known to be soft in the corners (even Rokinon admits it), but it shouldn't be a complete blur.

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08-07-2016, 10:50 AM   #3
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Alright I played with it more today and I MIGHT just be being too picky.
Set it up on a tripod and carefully took more shots at f8-f11 at what I felt was the sharpest I could get the trees across the lake.

https://drive.google.com/open?id=0BzL1myXZb9sdYUV6VFg2dzVUM2M

There's a link to a DNG file that's ~45MB. (Click the Download arrow at the top to get the actual file)
Would you be content/happy with this result?
08-09-2016, 07:15 AM   #4
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QuoteOriginally posted by eliphas Quote
There's a link to a DNG file that's ~45MB.
Just post some JPEG crops of the problem areas pls.
(I personally don't like the idea of downloading 45MB DNG's from stranger's Google Drives).

08-09-2016, 08:16 AM   #5
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I wouldn't need to download the file. It is unacceptably soft across the frame (assuming that Google Drive is not heavily compressing the file). Most likely it is the lens. I would do at least one more test, taking f/8 distance photos at infinity, 3m, 2m, 1.5m. The sharpest most likely will come at 2m - that's where mine is at for infinity. The 14mm is so wide, live view focusing can be challenging for certain scenes. It would work well for a newspaper (and that's another good test), but not for most landscape situations. I don't have the K-1, but that big, bright viewfinder might be better for focusing in good light than focus peaking.

Not having shot the 14mm on FF, I have no idea how soft it would be in the corners (especially if you feel strongly about correcting the significant distortion on FF). On the K-3 and other crop lenses, it is amazingly sharp into the corners.

Nothing in the album linked below is remarkable, just chronicling a day outing - but it happens that they all were taken with the Samyang 14mm (designated 12mm in EXIF). Even the low light inside photos are pretty sharp across the frame:
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08-10-2016, 06:46 AM   #6
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Actually, now that I have magnified the image trying to determine point of focus (difficult to find stopped down to f/8-11), it clearly is sharpest near the close shoreline - probably about 20 feet away. The lens is not focused near infinity. I see no evidence that the lens is misaligned, as the edges are relatively sharp on both sides and the CA is very low.

Keep working with the lens. Perhaps you can do better using the viewfinder. Realign the lens if desired (I simply keep true infinity on the lens in mind and adjust accordingly), and set distance by estimating. On the K-3 and other crop cameras, I find that to be most accurate - at least for distance shooting.
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