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Rokinon/samyang 135mm with zwo cam

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#1 Kaldoris

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Posted 05 October 2022 - 06:09 AM

Hi there,

 

Beginner here, bought a samyang 135mm and used my Canon 2000d to start. Quickly got hooked and now I got myself a zwo 585mc. I asked the store I bought it what I need to use both together and they sold me the Canon-zwo T2 adapter.

 

I tried it yesterday and it seems that I can't get in focus I would have to push the focus ring past infinite. I started to read on the Web that there is those back focus problems and I have to find the right rings to get the cam at right place. 

 

Is it right that for a canon model samyang 135mm I have to aim for 44mm ?

If I measure  quickly (see image) I am already past 44mm, is the canon-zwo adaptor the wrong one ? Or I don't measure right ?

 

Thanks for your enlightenment.

 

Cheers 

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#2 mayhem13

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Posted 05 October 2022 - 06:51 AM

How far off are you from prime focus?…..the issues with the 135mm Rok/Samyang infinity stop are well known and documented. There is a fix to change the stop you can do yourself….google Niko Carver….he’s got a video on how to do it I believe 

 

there’s info here as well

 

https://www.cloudyni...infinity-focus/



#3 Kaldoris

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Posted 05 October 2022 - 07:24 AM

So it's a lense problem, nothing about a distance between the cam and the lense ? 

 

Because at infinite I only started to see blurry circles for the stars and its as if it would miss like quarter of a focus ring rotation to get something visible.


Edited by Kaldoris, 05 October 2022 - 07:26 AM.


#4 t-ara-fan

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Posted 05 October 2022 - 07:59 AM

I bet if you read the product description on the ZWO website you will start thinking about why you have the 5mm extender in your setup.

Read the specs for your camera (specifically the mechanical drawings).

And with that you will have solved your problem all by yourself. High five!!

#5 fmendes

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Posted 05 October 2022 - 08:45 AM


Is it right that for a canon model samyang 135mm I have to aim for 44mm ?

 

Yes, 44mm from the lens mount to the sensor. And your measurement seems correct, it looks like the assembly is too long. Which female ring did you use? If I remember right, there are two different lengths.

 

I wouldn't adjust the lens not knowing if you have the right setup.



#6 Kaldoris

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Posted 05 October 2022 - 09:09 AM

I bet if you read the product description on the ZWO website you will start thinking about why you have the 5mm extender in your setup.

Read the specs for your camera (specifically the mechanical drawings).

And with that you will have solved your problem all by yourself. High five!!

I was trusting the store I bought it, couldn't just go and scream for that, with my small experience. Do that's what I was afraid of, they didn't sold me the right adapter frown.gif


Edited by Kaldoris, 05 October 2022 - 09:09 AM.

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#7 t-ara-fan

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Posted 05 October 2022 - 10:01 AM

The lens is designed for a 44.5mm flange to sensor distance. That is standard Canon spacing.

Your ZWO camera has a 17.5mm flange to sensor distance.

So you need the EOS bayonet to M42 adapter to be 27mm long. Unscrew the 5mm spacer. If it is tight, try wearing rubber gloves when unscrewing. Or wrap it in cloth and use gooseneck pliers and possibly scratch it. Or buy a lens clamp wrench thingy of the correct diameter. My little spacers always get stuck.

Edited by t-ara-fan, 05 October 2022 - 10:02 AM.


#8 t-ara-fan

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Posted 05 October 2022 - 10:04 AM

Like this

PROfezzion 3-Pack Camera Lens Filter Wrench Kit for CPL UV ND Filter, Fit 37-52mm 55-72mm 77-95mm Lens Thread for Canon Nikon Sony Fujifilm Olympus Pentax & Other Camera https://a.co/d/6AwGLhF

#9 Kaldoris

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Posted 05 October 2022 - 11:36 AM

Thanks everyone.

 

Found this image on the Web that explains a lot to me, thought the adapter was in 1 peace.

 

Will try this.

 

Cya all

 

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