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Anyone else shooting a Samyang/Rokinon 135 have this issue?
  
 
bluloo
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p.1 #1 · p.1 #1 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


So, I posted a previous thread in which I noted that my copy of the SY135 had a large, internal flare under certain lighting conditions, and was particularly noticeable when stopped down.
Being unable to resolve the issue (ruled out adapter reflection, light leaks etc), and that it appeared to be something internal to the lens, I returned it.

See pic 1, at bottom of post, for most egregious example of the flare on the first lens.

Given the otherwise excellent IQ and affordability of the lens, I decided to roll the dice and recently ordered the same lens from B&H (open box, as new), and set out to test it.

To my surprise, it has a similar, but much less noticeable flare under similar lighting conditions, when stopped down.
Examining the lens further, I noticed an internal haze or ring of some sort, and wondered if that might be reflecting/capturing light under certain conditions, when the lens was stopped down.

The blemish circled in blue, in the photos below.
It is visible with the naked eye, from multiple angles, and from the front and rear elements - though it seems to be more prominent, viewed from the rear.

I almost always shot the (first) lens wide open, where it's not noticeable, so it was likely present from the get go, but I never noticed. I also never checked for the same sort of internal blemish on the first copy.

My lens is Nikon mount, FWIW.

I wonder if others with the same lens (regardless of mount) might look to see if theirs has a similar blemish. I just find it odd that two different lenses would have a similar issue, and think it likely effects multiple lenses.

I've submitted an exchange request to B&H, and asked them to verify the replacement lens has no such blemish.

Comments, insights, and observations appreciated.


Samyang 135 Internal Blemish by lareginl, on Flickr

Samyang 135 Internal Blemish by lareginl, on Flickr


Samyang 135 Internal Blemish by lareginl, on Flickr

Samyang 135 Internal Blemish by lareginl, on Flickr

Samyang 135 Internal Blemish by lareginl, on Flickr





Pic 1: Worst-case sample of internal flare, stopped down.




Jan 13, 2017 at 09:14 PM
formula4speed
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p.1 #2 · p.1 #2 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


That's bizarre, I just got one in Nikon mount from Adorama, so far haven't noticed any flare but I will try to remember to look at the lens closer when I get home tonight.


Jan 13, 2017 at 09:31 PM
bluloo
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p.1 #3 · p.1 #3 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


formula4speed wrote:
That's bizarre, I just got one in Nikon mount from Adorama, so far haven't noticed any flare but I will try to remember to look at the lens closer when I get home tonight.



That would be great. Flare pic was from first copy, the second wasn't nearly as bad.
Look closely for an internal element blemish, if you would.
Hope yours is solid.



Jan 13, 2017 at 09:35 PM
formula4speed
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p.1 #4 · p.1 #4 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


Just took a look through mine, looked at a plain wall and shined a light through it and I don't see anything like you have on your lens. Mine is a Rokinon and purchased new from Adorama about 2 weeks ago.

Maybe they had a bad batch that shipped to B&H?



Jan 13, 2017 at 10:48 PM
bluloo
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p.1 #5 · p.1 #5 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


formula4speed wrote:
Just took a look through mine, looked at a plain wall and shined a light through it and I don't see anything like you have on your lens. Mine is a Rokinon and purchased new from Adorama about 2 weeks ago.

Maybe they had a bad batch that shipped to B&H?


First one was purchased used from Amazon. This one was open box ("new"), from B&H.

In any case, something is definitely up.

Here's my lens illuminated with an oblique flashlight, at slightly different angles. Yikes. No wonder I'm seeing a "flare".

I wonder if it's excess dust settling on an internal element during storage or shipping. It's literally shaped like the aperture.

SY Blemish-7- by lareginl, on Flickr


SY Blemish-6- by lareginl, on Flickr




Jan 14, 2017 at 12:15 AM
Vcook
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p.1 #6 · p.1 #6 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


my goodness that looks terrible. Its so bad that I ran and checked mine to make sure it wasnt showing these signs. Mine is clean and clear as can be from what I can see. You've got some bad luck


Jan 14, 2017 at 04:04 AM
rico
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p.1 #7 · p.1 #7 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


All lenses will look bad with a bright enough light. That said, suppression of stray light is a weak spot in this otherwise awesome optic. Light within or outside the FX frame can easily generate excessive veiling glare, although I don't recall flaring or ghosts. In studio, I'm careful to flag the lights, and avoid white b/g if possible.


Jan 14, 2017 at 08:03 AM
rico
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p.1 #8 · p.1 #8 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


On review of some old pics, I notice a diffused central hotspot in some cases where incoming light was not flagged or blocked by a lens hood. I'll investigate all issues raised in this thread when I get my copy back (currently on loan).


Jan 14, 2017 at 10:05 PM
bluloo
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p.1 #9 · p.1 #9 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


rico wrote:
On review of some old pics, I notice a diffused central hotspot in some cases where incoming light was not flagged or blocked by a lens hood. I'll investigate all issues raised in this thread when I get my copy back (currently on loan).



Thanks. FWIW, I saw significant flare with the hood as well.



Jan 14, 2017 at 10:14 PM
AHPZuazua
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p.1 #10 · p.1 #10 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


Did u return it


Feb 04, 2017 at 01:24 AM
 

Search in Used Dept. 



bluloo
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p.1 #11 · p.1 #11 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


AHPZuazua wrote:
Did u return it


Yes.
Received a second copy, and a brief test didn't indicate similar issues. I have yet to shoot with the replacement lens though.



Feb 04, 2017 at 02:33 AM
rico
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p.1 #12 · p.1 #12 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


Finally formalized a flare test and the results, as I already expected, look pretty dismal. One doesn't appreciate the expertise of CZ to suppress stray light until the third-party lens steps up to the plate. In this area, the Rok 135 is generally mediocre in a 1950s Leitz kind of way, allowing many photons within the frame to spray all over the sensor. However, matters are much more severe when a light source gets in the frame, or within about 30° of the optical axis. Then we observe all manner of veiling glare, flare, and hot spots. The mix of effects will depend on the entry angle and f-stop. For some reason, many effects are only visible via LiveView while the OVF shows little.

I narrowed this report to one angle that gets past the OEM hood. Without the hood, troubles are visible and worse over a large angle. Light source was a double-AA Maglite placed on an arm which could be swung to explore different angles. Also on a swinging arm were barndoors to improve on the hood.





Row 1 shows flare at different f-stops with OEM hood installed and the Maglite taking maximum advantage. Row 2 shoulds vast improvement with barndoors conforming tightly to the frame. Row 3 shows Maglite and barndoors removed.

Inspecting the light path with barndoors installed leads me to believe the problem is reflection of stray light off the barrel interior behind the iris. This could be fixed with flocking and a rectangular baffle. Of course, that would incur engineering costs that we bottom-feeders avoid. While the Rok is otherwise a mind-bending performer, there is an argument for upgrading to the CZ Aposonnar 135/2.



Feb 14, 2017 at 11:20 AM
bluloo
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p.1 #13 · p.1 #13 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


Awesome test. Two thumbs up.

My first two copies seemingly had other issues too, namely large blemish/detritus on internal element(s).

Does your lens have the center blemish as well?
My current copy doesn't, and doesn't flare nearly as badly in the same off-center lighting conditions as did the previous copies.

Also, do not tempt me with tales of the APO...



Feb 14, 2017 at 04:02 PM
rico
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p.1 #14 · p.1 #14 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


No blemishes: the glass is crystal clear. Except for control of stray light, this lens is an optical equal to my Leica Apo-Telyt-R 280/4 at 10x the price. I'm lazy about hoods but, in this case, it's essential. Without it, a correctly-exposed white b/g will very severely degrade contrast. The applicable cinematographer tool is a matte box, and they all use one. I'm going to make my own out of cardboard since the real ones go for thousands of bucks.


Feb 14, 2017 at 09:03 PM
bluloo
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p.1 #15 · p.1 #15 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


I wonder if clip-on barn door(s), placed strategically, might work, or if the small section of the clip on the inside of the hood, might interfere with the image.

For me, a bright light source coming from the front-right side of the frame, was the biggest issue.



Feb 14, 2017 at 11:14 PM
rico
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p.1 #16 · p.1 #16 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


The OEM hood has decent construction—better than the plastic of the lens! I would not hesitate to hang some fabric barndoors off it: simply apply some Velcro to the hood exterior. Alternatively, retool the hood itself by flocking with velvet and mounting a rectangular cutout up front. That the hood is a bayonet design means the cutout will always be correctly oriented.

Edited on Feb 14, 2017 at 11:30 PM · View previous versions



Feb 14, 2017 at 11:29 PM
bluloo
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p.1 #17 · p.1 #17 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


I wonder if clip-on barn door(s), placed strategically, might help, or if the small section of the clip on the inside of the hood, might interfere with the image.

For me, a bright light source coming from the front-right side of the frame, was the biggest issue.

Also, based on my earlier work with the issue, there's an exposed ribbon cable and semi-reflective metal surface just above it that covers the electronic connectors for the lens, at about 11:00-12:00 (from the rear of the lens, when the lens is mounted and the camera is level) that would be exposed as the rear element moved forward, when the focus was zoomed, and approximately when the reflection was most prominent in the frame.

There's also a reflective metal arm that runs just along the inner baffle, that may be reflecting stray light as well - assuming that area is the culprit.

IIRC, the most prominent reflection was present when focusing the lens, based on the focusing scale, from around 7'-5' or so, which coincides with greater exposure of those surfaces.

Maybe some extra thin gaffer's tape would work.



Feb 14, 2017 at 11:29 PM
rico
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p.1 #18 · p.1 #18 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


Yeah, I was testing at 5-7' ft, it being my regular working distance in the studio. Maybe the flaring clears up nicely at infinity. Ha, ha.


Feb 14, 2017 at 11:33 PM
rico
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p.1 #19 · p.1 #19 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


@bluloo, Eureka, I found the internal reflection!





With hood mounted, the range of vulnerable angles is narrow but with severe flaring outcome as demo'ed above. To find the internal reflection, lens and camera were disconnected. After finding the worst angle for flare, I removed the camera and could see the problem site immediately. Swinging the Maglite a tiny amount showed the pool of stray light being cut off by the hood. Aperture for this experiment was f/5.6.



Feb 15, 2017 at 05:41 AM
bluloo
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p.1 #20 · p.1 #20 · Anyone else shooting a Samyang/Rokinon 135 have this issue?


Nice work.

So, this is looking like a design flaw that's not amenable to a simple DIY fix - a la blackout of internal surfaces...

I wonder, would a flared extension, added to the end of the existing hood, partially mitigate the problem? - and/or perhaps a different shape to the hood?



Feb 15, 2017 at 03:46 PM
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