Frustrated w/new Rokinon14: coma and vingetting

Hello all,

I purchased the Rokinon 14mm 2.8 for my Sony A7RII (un-mod) after hearing all the great things about this lens. After my first test of the lens I was disappointed. At first I thought I might have bumped the camera during the exposure, but I think this is coma. Also the vignetting is high. 30sec ISO800 F 2.8, single exposure.

This is a JPEG size of the original unedited photo:



This is the modified picture in LR



Also, there does not seem to be a lens profile for the Rokinon lenses in LR. The milkyway also did not have any color which I know I can't blame on the lens. This was a relatively dark sky region.

I'm not sure if I just have a bad copy I have been hearing about or I am not post-processing this correctly in LR-CC.

C&C would be much appreciated.

I am considering selling this lens and getting a Canon 16-35/2.8 with the Metabones IV converter. Any thoughts on this lens for astrophography and as a general carry around lens.

Thank you in advance for any help.

Marc

You have a very bad lens !! All of the distortion is on the left half/ 2 thirds of the image while the right is "OK". There's nothing you can do about the vignetting, ALL lens's have it wide open. But your star trails, where they are clean, are still worse than your de-centered optics. I'd cut your exposure to 15 sec. That's the problem with a 42.5 MP cam. Shoot the the same thing at 24 MP and you'd be fine.

"I am considering selling this lens and getting a Canon 16-35/2.8 with the Metabones IV converter. Any thoughts on this lens for astrophography and as a general carry around lens."

Since you're not actually taking AP's, but rather "nightscapes", and trying to force the issue of maximum f ratio, high ISO,short exposures, good luck finding any lens that will work "perfectly" with the A7RII. Lens manufactures are lagging far behind the advances in sensors. You're trying to shoot a MF resolution camera with antique 35mm lens'.

id go with a rokinon 24mm 1.4seid to be one of the best lens made for nightscapes, it has something like 4 times the actual aperture size (aperture size equals focal length divided by f number) of youre 14mm. so you're going to get lots more detail. there are drawbacks however. you will need a shorter exposure- something like 13 or 15 seconds.

The rokinon lenses have decent performance, and a great price/performance ratio.

However the quality control just sucks.

I had to buy and return two 14mm lenses until I got a good one.

I have just returned THREE 24mm lenses, which seem to be even worse.

If you just dig through a bunch of them, you will eventually get a good one.

-- TREASURE it --

The key is to buy from a retailer that will allow multiple returns until you get a good one.

-- Rick

Thank you everyone for your input. I purchased this lens from Amazon back in the beginning of December so I guess I'm out of luck on a return for now.

Marc,

Although it is too late to return it to Amazon. You can return it to Rokinon. They will look at it and replace it with a new one. Yours definitely shows a lens tilting problem. The turnaround is usually 1-2 months.

Wade

Thank you!!!!

Marcster said:

Hello all,

I purchased the Rokinon 14mm 2.8 for my Sony A7RII (un-mod) after hearing all the great things about this lens. After my first test of the lens I was disappointed. At first I thought I might have bumped the camera during the exposure, but I think this is coma. Also the vignetting is high. 30sec ISO800 F 2.8, single exposure.

This is a JPEG size of the original unedited photo:



This is the modified picture in LR



Also, there does not seem to be a lens profile for the Rokinon lenses in LR. The milkyway also did not have any color which I know I can't blame on the lens. This was a relatively dark sky region.

I'm not sure if I just have a bad copy I have been hearing about or I am not post-processing this correctly in LR-CC.

C&C would be much appreciated.

I am considering selling this lens and getting a Canon 16-35/2.8 with the Metabones IV converter. Any thoughts on this lens for astrophography and as a general carry around lens.

Thank you in advance for any help.

Marc

Click to expand...

That looks exactly like a copy I just received, but in the Bower name. A rep from Rokinon confirmed that the 14mm 2.8 lenses that look exactly like the Samyang or Rokinon ones are not affiliated with Samyang optics anymore and can be cheap Chinese knock offs. It went back to the store and I got a Nikon 20mm f/1.8G Nano, which I'm waiting for its arrival.

I simply cannot waste my time or effort ordering copy after copy to find a good one.

Thank you, I'm thinking about getting a Sony or Canon 16-35/ F4 for my A7RII. I guess I'm losing one stop from 2.8 but I have a much more versatile lens I can use all the time. Please let me know how it goes with the Nikon 20mm/1.8. I was also considering the Tamron 15-30 2.8 but not sure if the converter will allow it to focus on my Sony. Not sure which will work well for the stars.

I know Sony makes an A-mount 16-35 2.8 for 2k and I'm not sure if all the cost with the converter to e-mount is worth it. Also Sony might come out with new lenses soon.

A couple of things. First of all you can bump up the ISO to at least 1600 or even higher. A 30 second shutter speed is too long if you are not tracking. The centre looks fairly good however you have problems in the corners.
I would say there is nothing wrong with your lens the distortion and vignetting in the corners is normal wide open. This lens performs best at f4 and if you shoot at 1600 or higher you will get better results. You may also want to look into a star tracker as well

I consider myself to be somewhat of a Rokinon "expert" having purchased many of these lenses, mostly in the 14mm and 24mm sizes for full frame.

YES, they are very good lenses in terms of relative performance.

YES, a best buy at the price

NO, you are not likely to get a good copy on your first try.

I have a GOOD 14mm F2.8 that is my workhorse lens for night landscapes. My third copy was good and a keeper.

I have a MEDIOCRE 24mm and trying to get a good one. I am on my FIFTH copy. Once I find the GOOD one, I will treasure it forever.

Many of these copies would have been OK to fine for normal daytime photography. Stars are a tough test for any lens. There aren't many alternatives out there anyways, and almost none in this price range.

Make sure to purchase from a vendor with easy returns ...

-- rick

Hi Rick, what do you think, do I have a bad lens? Some on the post say yes and some say no. Thank you.
--
Marcster

I have had Samyang 14 and a friend too. I had a good copy, my friend had a bad. Your images looks like his.



/Stefan

Marcster said:

Hi Rick, what do you think, do I have a bad lens? Some on the post say yes and some say no. Thank you.
--
Marcster

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