17 replies to this topic

[elakrab]

Hi,

 

I just got a Samyang 135mm f2 and ... big bummer, the focus cannot reach infinity by really little   

 

I know that in many cameras there are some focusing adjustment screws hidden in the focusing rubber or somewhere else. Is that the case of the Samyang/Rokinon? Anyone has manipulated those to move the focusing a bit to allow infinity focus? 

 

Big thanks

[B 26354]

Doesn't sound right, to me. I've never encountered a standard camera lens that couldn't focus at infinity... and these days, digital-camera lenses reach focus beyond infinity. If you bought it new... return it for a replacement. If you bought it used... return it for a refund.

[elakrab]

Nevermind, I just did some quick surgery on the samyang and now it focuses correctly to infinity as it is supposed to be without the stopper getting in the middle . The procedure is similar to the one for their 85mm and other manual prime lenses. Not the first lens I have to do this to but definitely one of the easiest ones https://www.dyxum.co...topic76615.html

 

So, instructions:

 

1) Peel the rubber out 

2) remove the 3 screws at 120 degrees. That will allow to retreat the focuser ring and access the stopper silver colored plate with its two screws. Move a bit the screws so that the stopper allows to move past infinite (the adjustement is just of a couple of mm, not more).

3) fix again the 2 adjusting screws to fix the stopper to its new position.

4) move the focuser tube back to its place and check (in my case I did it with a star) the focusing point to infinite so that we can put the focuser with its scale back to its correct position.

5) screw back in the 3 120 degrees screws.

6) Put the rubber band back in

 

Enjoy the lens .

[elakrab]

Doesn't sound right, to me. I've never encountered a standard camera lens that couldn't focus at infinity... and these days, digital-camera lenses reach focus beyond infinity. If you bought it new... return it for a replacement. If you bought it used... return it for a refund.

 

It doesn't depend on the camera, it depends on the lens, the backfocus and how the stoppers are set (if there are stoppers). Not the first lens I encounter with this issue and tolerances are so low that it may change from unit to unit. Fortunately manufacturers know and if the lens is not a terrible one it should come prepared to be serviced this way. 

Edited by elakrab, 23 October 2019 - 01:02 AM.

[tkottary]

I have 2 of these and both of them stop right at infinity. Not a mm after that . I had to adjust spacers with 1600 and 071 to get them into focus. I will give this method a go once current projects gets done. 

[Traveler]

When i recieved a lens and i have to do what you did, i send it back...

[calypsob]

Very interesting! I would have returned it but now you have fixed it yourself. This may be helpful for ccd and cmos users who have slight spacing issues.

[B 26354]

It doesn't depend on the camera, it depends on the lens, the backfocus and how the stoppers are set (if there are stoppers). Not the first lens I encounter with this issue and tolerances are so low that it may change from unit to unit. Fortunately manufacturers know and if the lens is not a terrible one it should come prepared to be serviced this way. 

Thanks. I do realize that the issue isn't camera-dependent. What I didn't realize, is that this is a manual lens. Since this is a DSLR and digital camera forum, I just assumed that the lens was a typical auto-focus lens. I always focus my AF lenses manually, whether I'm shooting terrestrial or astro... so I'm used to having lenses that do not have infinity stops.

 

Good job, fixing it! 

[geldingmakr]

I have a rokinon 135 that reaches infinity focus on my stock canon, but not my modified canon. I imagine the focus is different with the filter removed and it’s just at the point for the rokinon to not quite reach focus. I am trying to manually adjust the stops. Here I adjusted what I believe to be the infinity adjustments. But there plastic washered screws in deep are still mechanically stopping it. Anyway advice?

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[satiephile]

Hi geldingmakr,

 

Did you ever get this to work? I have the same focus problem with my Rokinon 135 and I'm about to try the same thing.

[Kendahl]

I have Samyang's 14 mm, f/2.4 lens. I spent extra for it because published test photos were clearly sharper than photos from their f/2.8. The lens focuses fine at infinity when the indicator on the scale points to 3 meters. I decided to keep it since it works for my sole application of astrophotography. However, it's why I have written off Samyang/Rokinon and spend my money with Canon and Sigma.

[asanmax]

I still don't understand why they put that limit on manual lenses that prevents them from focusing slightly past infinity. Almost all modern Canon and Nikon lenses focus ring run past infinity and that is super helpful especially with temperature fluctuations when imaging. 

[NuovaApe]

I'm having Samyang 135 infinity focus issue after modding my Sony A7RII for "full spectrum".

 

That "sliding T bar" in the pic above was preventing getting anywhere near infinity.

I've totally removed it so there is no bump-stop at all and it still wont quite get to infinity - another mm or 2 and I think it'd be there!

 

I might be the victim of tolerances, or removing my IR blocker pushed it over the edge.

My 20mm Samyang got to infinity fine (after stripping that down too and fiddling with the inner silver wheel thing).

 

My only resort is possibly a clip-in clear filter (eg STC). Maybe that'll put some optical length back in. They're about £90 so it's a bit of a gamble.

If I knew the STC thickness, it's refractive index, and if I was any good at physics I could figure out if it'd work but alas a gamble it will be!

[geldingmakr]

I did finally get this to work  https://youtu.be/Yk2myVjAFlU

[robininni]

I did finally get this to work  https://youtu.be/Yk2myVjAFlU

Thanks for the link, I followed his instructions and now my Rokinon 135mm works with my modified DSLR at F2   Woo hoo!

[KLWalsh]

I have an H Alpha modified Canon M200.
With a Canon autofocus lens, it could reach infinity focus, but with a Rokinon manual focus, it could not.
Unfortunately, this Rokinon lens doesn’t have a rubber grip ring to move out of the way and likewise there are no screws for adjusting infinity focus.
I was able to achieve infinity focus with an easy kluge-y cheat: I added a 1.25 inch Astromania UV-IR cut filter onto the back of the lens. A few drops of slightly rubbery hot melt glue holds the filter in place.
The 1.25 inch filter cell allowed the filter to be placed flat and normal to the focal axis without disturbing the rear lens element and without sticking back too far and hitting the sensor. The 1.25 inch filter is large enough so I don’t get any vignetting. Nor does it cause chromatic aberration.
The thickness of the flat filter was sufficient to move the focal point back far enough to reach infinity and still have some focusing margin.

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Edited by KLWalsh, 09 September 2024 - 06:10 AM.

[Mikehuerto]

I did finally get this to work  https://youtu.be/Yk2myVjAFlU

Wow! I just had exactly this probkem with a Canon 6D and Samyang 135 - followed your instructions, and now move back and forth through CFZ to get focus!! Thanks!

 

Mike

[belliott4488]

I did finally get this to work  https://youtu.be/Yk2myVjAFlU

Me, too! My Rok 135mm had no trouble reaching focus when I used it with an L-eXtreme dual-band filter, but when I tried it tonight without the filter, it was just a bit short of focus at the infinity stop. I was able to follow the procedure in the video, and now I'm back to imaging on the same night!