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04-21-2014, 04:24 AM   #1
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Strange thing with Samyang 16mm

I went to take night sky shots tonight and found a weird thing about my new Samyang 16mm F2.0.
It's not easy trying to focus on stars with a manual lens and this lens made it harder.

I took half a dozen shots set to infinity then uploaded them the my computer and discovered they were all very out of focus.
So then I went back out and took another 10 shots, moving the focus ring slightly away from infinity with each shot.
I found true infinity to be a long way from where the ring actually stops. Now I know some lenses can be slightly of the mark but I feel this one is just too far out.

Ok so I thought I might check the other end just to see what happens.
The specs for this lens say closest focus is at 20cm, well my copy will focus at 8cm. That's a bonus that I like, but one of the main reasons I purchased this lens in the first place was for star shots and the way the focus ring markings are placed makes that a real chore.

Now for the pics.
First one shows infinity stop.
Second one shows actual infinity position.
Third is close up stop.

Should I send this lens back and get a replacement ?








Last edited by chromo; 04-21-2014 at 05:59 AM.
04-21-2014, 04:58 AM   #2
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This has always been a problem of the wide angle samyangs. Had to adjust both my 8mm and 14mm. I imagine this design is very similar to mine. You can easily adjust it yourself. Lift the rubber on the focus ring slightly until you expose the screws. Then set the infinity now at the accurate infinity position. Unscrew the screw (not needed to remove them just slightly loosen). Set the infinity symbol to where it's supposed to be. Retighten them and cover w the rubber. All in all 5 min of work. Your Next lens will prob also have this problem. :/
04-21-2014, 05:20 AM   #3
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QuoteOriginally posted by oxidized Quote
This has always been a problem of the wide angle samyangs. Had to adjust both my 8mm and 14mm. I imagine this design is very similar to mine. You can easily adjust it yourself. Lift the rubber on the focus ring slightly until you expose the screws. Then set the infinity now at the accurate infinity position. Unscrew the screw (not needed to remove them just slightly loosen). Set the infinity symbol to where it's supposed to be. Retighten them and cover w the rubber. All in all 5 min of work. Your Next lens will prob also have this problem. :/
That sounds ok but is it the external ring that hits the stops or the internal mechanism ?
because if it's the external ring and I adjust it to the correct mark, it will still be way past where infinity really is.

What I mean is, if I could adjust the mark to where the stop is, then I can find infinity even in the dark. Else the stop will still be past infinity.

It's a confusing issue.

Last edited by chromo; 04-21-2014 at 05:35 AM.
04-21-2014, 06:18 AM   #4
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The physical stop is on the focus ring itself. If set infinity at the right place, you will no longer be able to go past it. Not sure if this answers your question.

04-21-2014, 07:18 AM   #5
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QuoteOriginally posted by oxidized Quote
The physical stop is on the focus ring itself. If set infinity at the right place, you will no longer be able to go past it. Not sure if this answers your question.
Yes that's what it should be so I'll try that adjustment.
Thanks
04-21-2014, 08:24 AM   #6
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the lens doesn't have a hard infinity stop. This is done so that : a) less QC and precision is needed, which lowers costs and b) it guarantees that infinity will be somewhere on the ring and not "beyond" it. This also helps because the temperatures can affect materials and throw off the distance scales
Finally, there was much debate over whether the Samynag 14mm has distance scales calibrated for Canon instead of Pentax, which would be just a mistake.

But your lens is behaving normally. The problem with adjusting it is that its difficult to tell where infinity is through the viewfinder and you don't want to accidentally prevent the lens from reaching infinity.

Also, the minimum focus distance is not 8cm. The MFD measures from the sensor to the closest possible subject, NOT from the front of the lens (that is usually called working distance). So if you take 8cm+lens length+register distance, you will notice the MFD is not actually far off
04-21-2014, 08:42 AM   #7
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QuoteOriginally posted by chromo Quote
I found true infinity to be a long way from where the ring actually stops. Now I know some lenses can be slightly of the mark but I feel this one is just too far out.
Welcome to the World of Samyang. Why they can't properly calibrate their wide angle lenses at the factory is a mystery. Fortunately they are easy to adjust.


Steve
04-21-2014, 10:37 AM   #8
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My Samyang 16mm does the same. I found it frustrating at first before I realized they're not the only manufacturer that does this. I recently purchased a Sigma 10-20mm F3.5 EX (which sells new for around $700) and it does the same.
I actually like this feature because the ability to focus beyond infinity means you will always have the ability to focus at infinity. Albeit, it will take more effort to do manually, because you have to check your focus instead of blindly turning the focus ring until it hits the end.
I've owned two Pentax lenses (one was a Limited lens ) and a Tamron lens that had infinity stops and were unable to focus at infinity. I'm assuming it was due either poor quality control or things loosening with time. Either way, I wouldn't have had to dismantle these lenses to fix them if they had the ability to focus beyond infinity built into the design like your Samyang.
If you're using this lens with a camera that has live view (magnification), and focus peaking (added bonus), it should be fairly easy to focus manually at infinity.


Last edited by geomez; 04-21-2014 at 02:01 PM. Reason: Had to change "many fracture" to manufacturer. Stupid autocorrect makes me look like a dunce.
04-21-2014, 10:52 AM   #9
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QuoteOriginally posted by stevebrot Quote
Welcome to the World of Samyang. Why they can't properly calibrate their wide angle lenses at the factory is a mystery. Fortunately they are easy to adjust.


Steve
I don't think it is a Samyang thing. Many modern lenses allow the focus go pass infinity slightly, I read somewhere it is to avoid hard stop due to the strong motor that modern camera uses that drive AF.
My PENTAX 16-50 is like that (though not that much off).

If you read how to take night skies tutorial, most would suggest you find out your lens 'true infinity' before dark and switch to MF and tape the focusing ring.

so definitely not a Samyang thing.
04-21-2014, 11:01 AM   #10
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QuoteOriginally posted by LFLee Quote
I don't think it is a Samyang thing. Many modern lenses allow the focus go pass infinity slightly, I read somewhere it is to avoid hard stop due to the strong motor that modern camera uses that drive AF. My PENTAX 16-50 is like that (though not that much off).
That may be one reason for it, but in the case of Samyang it is not. Their lenses, including the one in question are manual focus lenses.
04-21-2014, 11:20 AM   #11
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No one mentions this (and I haven't used it) but a fast wide lens like this may suffer from severe focus shift. I recall one of the reviewers (of the Samyang 8mm lens) mentioning the Samyang fish eye was likely (on purpose) properly scale focused to infinity at f/11. So before you adjust it to have a hard stop wide open at infinity, check the focus stopped down.
04-21-2014, 11:49 AM   #12
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This issue arises for star shots only as far as I can see.


The thing is, stars are always at infinity. None of them are ever any closer, the closest is I believe .3.5 light years away.


Therefore only one focus mark is ever needed for your astro work. So paint it on the lens where you determine the infinity point to really be and use that.
04-21-2014, 12:02 PM   #13
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QuoteOriginally posted by Imageman Quote
The thing is, stars are always at infinity. None of them are ever any closer, the closest is I believe .3.5 light years away.
Well, infinity for a lens!

Your comment about light years made me look up parsec vs. light year on Wikipedia, and I found this under Light-year:
"Although modern astronomers often prefer to use the parsec, light years are also popularly used to gauge the expanses of interstellar and intergalactic space.this is dumb as f**k"

Sorry for the (quoted) profanity, but this just emphasizes my skepticism about a "crowd-sourced" repository of knowledge... Maybe Samyang gets their QC protocols from Wikipedia as well?
04-21-2014, 12:13 PM   #14
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QuoteOriginally posted by panoguy Quote
Your comment about light years made me look up parsec vs. light year on Wikipedia, and I found this under Light-year: "Although modern astronomers often prefer to use the parsec, light years are also popularly used to gauge the expanses of interstellar and intergalactic space.this is dumb as f**k"
Funny thing, when you go to edit the wiki the last line doesn't show up in the editable text.
Maybe the wikipedia mods what it there.
04-21-2014, 01:20 PM   #15
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QuoteOriginally posted by geomez Quote
That may be one reason for it, but in the case of Samyang it is not. Their lenses, including the one in question are manual focus lenses.
Also consider that the matter of flaky infinity focus with the Samyang wide-angles is a frequent topic of discussion on this site, on the order of the same issue with the Zenitar 16/2.8 Fisheye. It might be good to also note that the calibration error is not always in the direction of "past infinity". Mine was the other direction. I view it as a final assembly/QA issue at Samyang that unfortunately casts a bad light on an otherwise good product.


Steve
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