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12-22-2023, 07:53 PM   #1
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Rokinon 16mm F2.0 on Pentax K-70, setup questions

Hello everyone, I wanted a wide angle, fast and not too expensive lens so I thought that the above mentioned would be a good compromise. I did some research and it looks like it is a decent lens and the review on this forum was encouraging.
The first impression is a good one and now I'm trying to familiarize with it but I still have some questions.
First is the question of the focal length. When starting up the camera with the new lens, I get a prompt to input the focal length but I only have the choice between 15mm and 18mm. I chose 15 which is closer but I wonder if there is a side effect or impact of this mismatch. What could possibly go wrong ?

Second, I am fully aware this lens is manual focus only so I'm now learning how to live without auto focus. Focus peaking in live view works as designed but I find it a little bit time consuming (the subject of my photos will have to be patient), however in viewfinder I see the red spot of the AF activating but I can not tell when and why. Is there a way I could make good use of this indicator in viewfinder (like when half-pressing the shutter button in AF) ?


Besides this, are there any other setting I should modify to accommodate this lens ?

12-22-2023, 08:42 PM   #2
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QuoteOriginally posted by nilie Quote
Hello everyone, I wanted a wide angle, fast and not too expensive lens so I thought that the above mentioned would be a good compromise. I did some research and it looks like it is a decent lens and the review on this forum was encouraging.
The first impression is a good one and now I'm trying to familiarize with it but I still have some questions.
First is the question of the focal length. When starting up the camera with the new lens, I get a prompt to input the focal length but I only have the choice between 15mm and 18mm. I chose 15 which is closer but I wonder if there is a side effect or impact of this mismatch. What could possibly go wrong ?

Second, I am fully aware this lens is manual focus only so I'm now learning how to live without auto focus. Focus peaking in live view works as designed but I find it a little bit time consuming (the subject of my photos will have to be patient), however in viewfinder I see the red spot of the AF activating but I can not tell when and why. Is there a way I could make good use of this indicator in viewfinder (like when half-pressing the shutter button in AF) ?


Besides this, are there any other setting I should modify to accommodate this lens ?
The only reason that the focal length needs to be entered is for Shake Reduction. No other effect or reason. Entering 15mm would be fine.
12-23-2023, 02:14 AM   #3
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Agree with Terry C. I have used 15mm with no problem. As for focus, I have found that infinity is most usual, at least for landscapes. My copy, and I have read that it is common, is that you can go beyond the infinity mark which will blur your image. Being particular about being on the mark should get a sharp photo. That said, and ain't there aways a "that said," the focus ring, at least on my copy, can move for no apparent reason. Double checking before the shot is prudent.
12-23-2023, 04:22 AM   #4
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Manual focusing needs to be practiced but is always useful.
However, a wide angle lens like the Rokinon 16mm, even at F/2, gives a lot of DOF so, most of time, you will successfully use hyperfocal rules.
At very small distances, focusing will remain difficult but you can use some tricks like live-view or viewfinder attachments. I own a Pentax Refconverter A, it is an angle viewfinder which can be switched between 1x and 2x magnification, it is sometimes very useful for close-up photos.

12-23-2023, 07:49 AM - 3 Likes   #5
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The red spot in the viewfinder is where the AF system would focus but it doesn't mean that you are focussed correctly. The green hexagon at the bottom of the viewfinder is what tells you if the camera thinks it is in focus.
12-23-2023, 08:03 AM   #6
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+1 came here to say green hexagon is focus confirmation
12-23-2023, 11:50 AM - 2 Likes   #7
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Learn to use the Hyperfocal distance scale on the lens
https://rokinon.com/cdn/shop/products/16mm-f20-high-speed-wide-angle-712694_...g?v=1647618377
The little scale between the red band and the focus distance, on either side of the wide, vertical, white band which indicates the focus point, you see the F/stops duplicated on each side of the point of focus.
Pick your f/stop, f/8, say, and set the infinity mark to align with the left hand f/8 on the scale, and you see the focus scale will align at about 1m on the right f/8 mark, everything between 1m and infinity will be in acceptable focus. If you want more depth, go for f/11 or 16, move the infinity point, less depth go the other way.
Using this method, in some situations, you can set it, use either Aperture preferred, or TAV, and not have to change anything, point, compose and shoot.
Just remember to reset your focus point anytime you change aperture.

12-24-2023, 12:56 PM   #8
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Thank you all for your answers.
Special thanks to K-Three for pointing me to information about Hyperfocal distance.
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