Rokinon/Samyang 16 mm F2 on Pentax K5-11. Won't open up to F2, stops at F4

Turtle1313 · 12-14-2021, 09:44 PM

I just purchased a Rokinon (Samyang) 16 mm F2 manual lens for my Pentax K-5 IIs body. The lens will go from F4 - F22, can't get it to reach F2.
Bought it for night photography, so really need the F2.
Followed the instructions, "A" set to distance line, on manual, AV, and aperture ring "prohibited".
Any suggestions? I know many people in forum have this lens and note how sharp it is at F2.
Thanks in advance!

Adam · 12-14-2021, 10:08 PM

Is it not stopping down past F4 when the aperture ring is set to A, or is it not stopping down when the aperture ring is set to F2? The former could be an issue with your contacts whereas the latter could mean the diaphragm has an issue. Does it stop down all the way if you move the aperture lever menually?

stevebrot · 12-15-2021, 12:39 AM

Originally posted by Turtle1313

Followed the instructions, "A" set to distance line, on manual, AV, and aperture ring "prohibited".

Set your camera to allow aperture ring by default. There is no reason to do otherwise. With "A" set at the index mark, the lens should behave the same as a manual focus Pentax-A series f/2 lens. Under those circumstances the camera body should be controlling both aperture and shutter speed.

Steve

**UncleVanya** · 12-15-2021, 04:59 AM

Originally posted by Turtle1313

I just purchased a Rokinon (Samyang) 16 mm F2 manual lens for my Pentax K-5 IIs body. The lens will go from F4 - F22, can't get it to reach F2.
Bought it for night photography, so really need the F2.
Followed the instructions, "A" set to distance line, on manual, AV, and aperture ring "prohibited".
Any suggestions? I know many people in forum have this lens and note how sharp it is at F2.
Thanks in advance!

With the lens off the camera does it open fully to f2 when the aperture is set to f2? Does it open fully when mounted on the camera - perhaps it is reporting wrong but still opening correctly?

**Michail_P** · 12-15-2021, 06:35 AM

Why set the aperture to prohibited?
Check the operation of the diaphragm manually see if that opens fully. Clean the lens’contacts.

ChristianRock · 12-15-2021, 07:27 AM

Yeah I would check the aperture manually first - set the aperture ring to f2 and see if it opens up all the way (with the lens detached from the camera). If it doesn't open up, you probably have an issue with the aperture blades.

How do you like the lens by the way? I've always been curious about it. I have seen good deals on it but the lens is heavier than my DA*16-50mm and I'm not sure I need the f2 at 16mm, so I always ended up deciding not to get it... it has better distortion control (exactly the same in fact as the DA 16-45mm f4 that I'm very familiar with...) and I guess better CA control, so I'm still curious about it...

Turtle1313 · 12-15-2021, 08:27 PM - **1 Like**

I talked to a friend who just suggested cleaning the contact points with alcohol and it worked! I how have F2.

Thank you all for suggestions. I just joined and it sounds like a wonderful group of folks.

ChristianRock ... I haven't had a chance to put it through its paces yet. I got it for $350 from B and H. I have the Pentax DA 16 - 45 mm F4 as well, which I really like. I've been using that to get acquainted with night photography, but it seems
like all the suggestions were for a faster lens, so I purchased this. Its a little heavier than the Pentax lens, but not bad, esp on a tripod. It seems that the reviews of the 16mm F2 lens were alot better than the F2.8 16 mm Rokinon/Samyang lens.

Read more at: Rokinon/Samyang 16 mm F2 on Pentax K5-11. Won't open up to F2, stops at F4 - PentaxForums.com

Turtle1313 · 12-15-2021, 08:29 PM

Originally posted by stevebrot

Set your camera to allow aperture ring by default. There is no reason to do otherwise. With "A" set at the index mark, the lens should behave the same as a manual focus Pentax-A series f/2 lens. Under those circumstances the camera body should be controlling both aperture and shutter speed.

Steve

thank you!

Turtle1313 · 01-02-2022, 08:07 PM - **1 Like**

Originally posted by photogem

And let us know how you proceeded!

Hi! I put an earlier post with the solution, but it is buried in the many kind suggestions from group members.

A friend suggested cleaning all the contacts with alcohol. It worked! If I remove the lens I have to re-clean the contacts,

but once the lens is on the body it continues to work.

To answer other questions, I was using the camera's aperature dial to change the aperature setting, and it only went down to F4.
It didn't involve manually using the lens' aperature ring. Once I cleaned the contacts, it was able to go all the way down.

Turtle1313 · 01-02-2022, 08:09 PM - **1 Like**

Originally posted by Adam

Is it not stopping down past F4 when the aperture ring is set to A, or is it not stopping down when the aperture ring is set to F2? The former could be an issue with your contacts whereas the latter could mean the diaphragm has an issue. Does it stop down all the way if you move the aperture lever menually?

You are correct! A friend suggested cleaning the contacts for the body and lens, and that did the trick.
The issue was that the camera body aperture dial would not dial down past F2. Now it does :-)
Thanks for your help.

**photogem** · 01-02-2022, 08:16 PM

Originally posted by Turtle1313

Hi! I put an earlier post with the solution, but it is buried in the many kind suggestions from group members.

A friend suggested cleaning all the contacts with alcohol. It worked! If I remove the lens I have to re-clean the contacts, but once the lens is on the body it continues to work.

To answer other questions, I was using the camera's aperature dial to change the aperature setting, and it only went down to F4.
It didn't involve manually using the lens' aperature ring. Once I cleaned the contacts, it was able to go all the way down.

Thanks for letting us know.
Usually I read all posts since the beginning your your answer somehow slipped my attention.
It is good and important to know how things proceeded.

Turtle1313 · 01-04-2022, 10:25 PM - **1 Like**

I"m guessing that I likely didn't click the right button to link it also. Everyone was wonderful with suggestions.

12-14-2021, 09:44 PM	#1
Turtle1313 New Member Join Date: Dec 2021 Posts: 6	Rokinon/Samyang 16 mm F2 on Pentax K5-11. Won't open up to F2, stops at F4 I just purchased a Rokinon (Samyang) 16 mm F2 manual lens for my Pentax K-5 IIs body. The lens will go from F4 - F22, can't get it to reach F2. Bought it for night photography, so really need the F2. Followed the instructions, "A" set to distance line, on manual, AV, and aperture ring "prohibited". Any suggestions? I know many people in forum have this lens and note how sharp it is at F2. Thanks in advance!

12-14-2021, 10:08 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	Is it not stopping down past F4 when the aperture ring is set to A, or is it not stopping down when the aperture ring is set to F2? The former could be an issue with your contacts whereas the latter could mean the diaphragm has an issue. Does it stop down all the way if you move the aperture lever menually? Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

12-15-2021, 07:27 AM	#6
ChristianRock Pentaxian Join Date: Jul 2013 Location: People's Republic of America Photos: Gallery \| Albums Posts: 9,912	Yeah I would check the aperture manually first - set the aperture ring to f2 and see if it opens up all the way (with the lens detached from the camera). If it doesn't open up, you probably have an issue with the aperture blades. How do you like the lens by the way? I've always been curious about it. I have seen good deals on it but the lens is heavier than my DA16-50mm and I'm not sure I need the f2 at 16mm, so I always ended up deciding not to get it... it has better distortion control (exactly the same in fact as the DA 16-45mm f4 that I'm very familiar with...) and I guess better CA control, so I'm still curious about it... Last edited by ChristianRock; 12-15-2021 at 07:34 AM.*

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12-15-2021, 12:39 AM	#3
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by Turtle1313 Followed the instructions, "A" set to distance line, on manual, AV, and aperture ring "prohibited". Set your camera to allow aperture ring by default. There is no reason to do otherwise. With "A" set at the index mark, the lens should behave the same as a manual focus Pentax-A series f/2 lens. Under those circumstances the camera body should be controlling both aperture and shutter speed. Steve

12-15-2021, 04:59 AM	#4
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,468	Originally posted by Turtle1313 I just purchased a Rokinon (Samyang) 16 mm F2 manual lens for my Pentax K-5 IIs body. The lens will go from F4 - F22, can't get it to reach F2. Bought it for night photography, so really need the F2. Followed the instructions, "A" set to distance line, on manual, AV, and aperture ring "prohibited". Any suggestions? I know many people in forum have this lens and note how sharp it is at F2. Thanks in advance! With the lens off the camera does it open fully to f2 when the aperture is set to f2? Does it open fully when mounted on the camera - perhaps it is reporting wrong but still opening correctly?

12-15-2021, 06:35 AM	#5
Michail_P Site Supporter Join Date: Nov 2019 Location: Kalymnos Photos: Gallery Posts: 3,006	Why set the aperture to prohibited? Check the operation of the diaphragm manually see if that opens fully. Clean the lens’contacts.

12-15-2021, 08:27 PM - 1 Like	#7
Turtle1313 New Member Join Date: Dec 2021 Posts: 6 Original Poster	I talked to a friend who just suggested cleaning the contact points with alcohol and it worked! I how have F2. Thank you all for suggestions. I just joined and it sounds like a wonderful group of folks. ChristianRock ... I haven't had a chance to put it through its paces yet. I got it for $350 from B and H. I have the Pentax DA 16 - 45 mm F4 as well, which I really like. I've been using that to get acquainted with night photography, but it seems like all the suggestions were for a faster lens, so I purchased this. Its a little heavier than the Pentax lens, but not bad, esp on a tripod. It seems that the reviews of the 16mm F2 lens were alot better than the F2.8 16 mm Rokinon/Samyang lens. Read more at: Rokinon/Samyang 16 mm F2 on Pentax K5-11. Won't open up to F2, stops at F4 - PentaxForums.com

12-15-2021, 08:29 PM	#8
Turtle1313 New Member Join Date: Dec 2021 Posts: 6 Original Poster	Originally posted by stevebrot Set your camera to allow aperture ring by default. There is no reason to do otherwise. With "A" set at the index mark, the lens should behave the same as a manual focus Pentax-A series f/2 lens. Under those circumstances the camera body should be controlling both aperture and shutter speed. Steve thank you!

01-02-2022, 08:07 PM - 1 Like	#9
Turtle1313 New Member Join Date: Dec 2021 Posts: 6 Original Poster	Originally posted by photogem And let us know how you proceeded! Hi! I put an earlier post with the solution, but it is buried in the many kind suggestions from group members. A friend suggested cleaning all the contacts with alcohol. It worked! If I remove the lens I have to re-clean the contacts, but once the lens is on the body it continues to work. To answer other questions, I was using the camera's aperature dial to change the aperature setting, and it only went down to F4. It didn't involve manually using the lens' aperature ring. Once I cleaned the contacts, it was able to go all the way down.

01-02-2022, 08:09 PM - 1 Like	#10
Turtle1313 New Member Join Date: Dec 2021 Posts: 6 Original Poster	Originally posted by Adam Is it not stopping down past F4 when the aperture ring is set to A, or is it not stopping down when the aperture ring is set to F2? The former could be an issue with your contacts whereas the latter could mean the diaphragm has an issue. Does it stop down all the way if you move the aperture lever menually? You are correct! A friend suggested cleaning the contacts for the body and lens, and that did the trick. The issue was that the camera body aperture dial would not dial down past F2. Now it does :-) Thanks for your help.

01-02-2022, 08:16 PM	#11
photogem Site Supporter Join Date: Apr 2015 Posts: 3,525	Originally posted by Turtle1313 Hi! I put an earlier post with the solution, but it is buried in the many kind suggestions from group members. A friend suggested cleaning all the contacts with alcohol. It worked! If I remove the lens I have to re-clean the contacts, but once the lens is on the body it continues to work. To answer other questions, I was using the camera's aperature dial to change the aperature setting, and it only went down to F4. It didn't involve manually using the lens' aperature ring. Once I cleaned the contacts, it was able to go all the way down. Thanks for letting us know. Usually I read all posts since the beginning your your answer somehow slipped my attention. It is good and important to know how things proceeded.

01-04-2022, 10:25 PM - 1 Like	#12
Turtle1313 New Member Join Date: Dec 2021 Posts: 6 Original Poster	I"m guessing that I likely didn't click the right button to link it also. Everyone was wonderful with suggestions.