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Samyang 135 Star colors issue

Canon EOS 700D / Rebel T5i / Kiss X7i Artifacts Help Needed
Samyang 135 f/2 •4 replies•394 views
Ali Alhawas avatar
Ali Alhawas avatar
Hi all,

Got the Samyang 135 2 years ago, but unfortunately never get a good image..
the issue as you can see in the picture is strange star colors .. its look like the stars color have 2 different  settings..
see left and right stars colors .. the left part got greenish blue stars while the right part look normal..
Any idea what caused this weird difference ?

Modified Canon 700d - Samyang 135 at f2.8

Thanks in advance
patrick cartou avatar
patrick cartou avatar
Hi Ali

Maybe a stacking problem rather than a lens issue ?
CS

Patrick
Hartmuth Kintzel avatar
Hartmuth Kintzel avatar
I think it could be the lens.
The stars on the left don't seem sharp either.
That could be a badly corrected single lens affecting mostly blue light.
It shouldn't be a tilted lens because the transition is very rough.
Unfortunately, the Samyang 135 has a relatively strong fluctuation in quality.
I also had to swap mine out first to get one of good quality.

CS
Hartmuth
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Marco van der Kooij avatar
Marco van der Kooij avatar
Hi,

Based on what i see it is much more likely you have a combination of acquisition and adapter problems (in that order).

you have to first exclude having obvious acquisition problems like polar alignment, autoguiding, flex etc.

After having dealt with those issues you might experiment by rotating the lens, the adapter and look for additional problems.

It is not straightforward to pull all information from the lens to its potential so you want to make sure you do it right.

You might measure the star resolution and eccentricity throughout your image in order to obtain a more accurate quantitative assessment as opposed to qualitative assessment you posted.

Good luck

Marco
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Peter Pat avatar
Peter Pat avatar
This looks a bit like you might have some tilt (non orthogonality) - could be a lens issue of course.
I've been using this lens for a while and have found that focus is absolutely critical - if you're out by even a tiny amount it has a big effect on the resultant image. Perhaps try some test images with focus slightly shifted either side of what you think is perfect focus and see if there are any differences?
Perhaps also try shooting directly overhead vs at a low angle & compare. Hope you get it sorted.
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