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06-28-2018, 05:28 AM   #1
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Zenitar-K 16mm f/2.8 - infity focus & diaphragm

Greetings everyone !

I recently (today 06/28/2018) received a new lens, as you read in the title, the Zenitar-K 16mm f/2.8, but i'm facing problems with it. First, I read somewhere that you're unable to achieve infinity focus with a filter on the lens (the back filter) so I put the transparent filter, so yeah it's better but i'm still unable to infinity focus :c (I also niticed that there's a gap between the... hood? / Frontal part of the lens and the focusing ring. From what i've seen on the internet that seems pretty normal but I just wanted to say that just in case.

And the most important problem, my K30 is unable to control the diaphragm, sometimes it works in live view but not every time... like 1 time on 4 (did I said this right ?). When I press "optical previsualisation", nothing happens, is that because it lacks contacters so the body thinks it is impossible to operate the diaphragm ? (I specify that I authorized the use of the diaphragm ring)

Anyway, if someone can help we with one of these problems, I'll be very grateful.

I highly apologize for my mediocre English too

\/ an example photo, I was at the infinity. (in red = the "in-focus" area) \/

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06-28-2018, 05:42 AM - 1 Like   #2
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Regarding infinity focus, this is a common problem with the lens and appears to be due to poor QC at the factory.

A comment from one of our user reviews reads:

"If you have soft images at infinity, the infinity stop can be adjusted in one way or another by peeling back the focus ring, loosening (but not removing!) the screws and resetting the focusing ring a little left or right. I adjusted mine to give about 1 mm more towards infinity focus, and I got marginally sharper images. I doubt every lens needs this adjustment."

I didn't have to perform any adjustment on mine, but it sounds like yours needs it.

As for the intermittent diaphragm control... I can't speak from experience, as my own copy of the lens is in M42 mount, but it potentially sounds like there may be a conductivity problem with the lens mount. Is it a painted or coated mount, perhaps? And if you use other manual K-mount lenses with shiny silver mounts, do they work correctly?
06-28-2018, 06:05 AM - 1 Like   #3
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Infinity focus is easy to adjust, exactly as described in Mike's (BigMackCam's) post. I tested my copy both with the clear rear filter and without, and sharpness and contrast were much better without the filter. Since you're going to have to adjust infinity focus anyway, I'd recommend using the lens without any rear filter at all and setting the infinity focus to work that way.

It's really only worth setting the lens up to work with a rear filter in place if you specifically want to use the coloured filters for some reason, such as shooting B&W film.

I can't give any suggestion about the aperture linkage, as mine is the M42 version.
06-28-2018, 07:54 AM   #4
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Thanks everybody !

About the diaphragm, it's okay, that's just that the camera would not change its speed setting, but it doesn't really matters since it can be easily adjusted in post-treatment (production?)

And about the focus ring, i'll try out, so without the filter. thanks everyone !

06-28-2018, 08:45 AM   #5
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As noted above, the infinity adjustment is easy and even easier if using magnified live view. A significant improvement in performance should be the result. In regards to the clear rear filter...Yes, some users swear that it makes no difference. I tested mine (after adjusting the infinity focus) with the clear filter both on and off and found that quality was noticeably better with it on.

The matter of the aperture operation is more serious. Check actuation with the lens OFF the camera by flicking the lever lightly while looking through the rear of the lens. The action should be snappy and without hesitation at all positions of the aperture ring. The lever itself should not be bent or crooked and should look like the actuator on any other K-mount lens, free of evidence of flaw or damage and positioned parallel to its guard. I just checked my copy and noted some sluggishness due to oil fouling the aperture blades (not happy). With time, oil fouling will result in extreme sluggishness and the lens not properly stopping down for exposure. If the aperture is not working properly off-camera and/or shows evidence of damage, a return trip to the seller should be in order.


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06-28-2018, 08:58 AM   #6
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QuoteOriginally posted by RedTurian Quote
About the diaphragm, it's okay, that's just that the camera would not change its speed setting, but it doesn't really matters since it can be easily adjusted in post-treatment (production?)
The lens will not stop down unless the camera is in M, B, or X modes. For information about use of older lenses lacking the "A" contacts, see:
Using Manual Lenses (M42 Screwmount, M , K) on Pentax DSLRs F-- - PentaxForums.com
QuoteOriginally posted by RedTurian Quote
And about the focus ring, i'll try out, so without the filter. thanks everyone !
Calibrate infinity focus with the clear filter on and then check to see if well-focused photos* are worse or better with it off. That should be evidence enough. That and the fact that they are delivered from the factory with the filter in place. Think about it a bit...Why would they include a rear-mount clear filter in the kit and why is it mounted as such from the factory? A good copy of the Zenitar 16/2.8 offers very good performance at f/4 and excellent sharpness from f/5.6 down to around f/16. Results should be crisp.


Steve

(...bought my copy new in 2008, delivered in factory box with wrappings and internal packing intact...)

* There is a persistent myth that ultrawides and fisheyes in particular offer focus-free operation due to near-infinite DOF. While most such lenses are difficult to focus (everything is soooo teeny), the DOF is far from infinite, particularly for near and moderately near objects. Attention to focus pays a dividend with the Zenitar, even if it means working on tripod in live view.

Last edited by stevebrot; 06-28-2018 at 09:10 AM.
06-28-2018, 09:30 AM   #7
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QuoteOriginally posted by stevebrot Quote
The lens will not stop down unless the camera is in M, B, or X mode.
X mode? what is that? and yeah, I allowed the use of the aperture ring.

QuoteOriginally posted by stevebrot Quote
Calibrate infinity focus with the clear filter on and then check to see if well-focused photos* are worse or better with it off. That should be evidence enough. That and the fact that they are delivered from the factory with the filter in place. Think about it a bit...Why would they include a rear-mount clear filter in the kit and why is it mounted as such from the factory? A good copy of the Zenitar 16/2.8 offers very good performance at f/4 and excellent sharpness from f/5.6 down to around f/16. Results should be crisp.
Yeah but since the clear filter is not coated, I expect, like Dartomoore Dave said, that the shots will be way more contrast-ey without the filter, and probably sharper too, but what you said make sense. And I trust you about the crisp results, but I lack magnetized precision screwdrivers right now.
06-28-2018, 10:10 AM   #8
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Infinity focus... set the lens to f8, and you get focus on everything! (Joking/not joking).

06-28-2018, 10:17 AM   #9
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QuoteOriginally posted by RedTurian Quote
Yeah but since the clear filter is not coated, I expect, like Dartomoore Dave said, that the shots will be way more contrast-ey without the filter, and probably sharper too, but what you said make sense. And I trust you about the crisp results, but I lack magnetized precision screwdrivers right now.
You don't need magnetized screwdrivers. When adjusting infinity focus, the grub screws are backed out to release the ring, not removed. Do as you please with the rear filters. My experience was reduced sharpness away from center with no improvements in contrast or image quality. Of course, that was after I corrected the focus issue. I have made some spectacular prints at 13x19" from captures done with my Zenitar and have no complaints about optical quality. For a sampling of both film and APS-C digital (some much better than others and some much more fishy than others), see my Flickr album:
Zenitar Fisheye | Fotostevia on Flickr
The Flickr Zenitar Fisheye group is a source of inspiration as well as pertinent discussions.
Zenitar 16mm Fisheye | Flickr
BTW...Welcome to the Pentax Forums!

Almost forgot...X-mode is on the mode dial as a red "X" and is basically M mode with only one shutter speed, the X-sync speed for flash.
Steve

Last edited by stevebrot; 06-28-2018 at 10:25 AM.
06-28-2018, 10:22 AM   #10
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QuoteOriginally posted by RedTurian Quote
and yeah, I allowed the use of the aperture ring.
In M mode, you would then use the green button to do stop-down metering, as per stevebrot's link.
06-28-2018, 10:34 AM   #11
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I was joking above, but I will say, this lens is brilliant at f8 to f16 (I own two copies, a k mount and a m42), and I strongly suggest you find ways to stick around there. Purely my own opinion, based on shooting with the two lenses.
06-28-2018, 10:43 AM   #12
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QuoteOriginally posted by bobbotron Quote
Infinity focus... set the lens to f8, and you get focus on everything! (Joking/not joking).
Unfortunately, for a maladjusted Zenitar the problem is usually severe enough that even at narrow apertures very little in the frame is in focus regardless of focus ring position or aperture. For a well-adjusted lens, the rules for DOF at 16mm still apply. At f/8, the hyperfocal is at 5.3' on APS-C. If the subject is at 3' (not unusual for fisheye), DOF drops to 4.9' with far limit at a little short of 7'. I have learned to be aware of focus when working with the Zenitar.

My Rokinon 8/3.5 Fisheye, OTOH, is quite another beast. In the community of owners, the common advice is to tape the focus ring at 6' and shoot Av at f/8. (Hyperfocal is at 1.3' at f/8.). Unfortunately, my Rokinon also required infinity focus adjustment...not easy with that lens, even with magnified live view.

QuoteOriginally posted by bobbotron Quote
I was joking above, but I will say, this lens is brilliant at f8 to f16 (I own two copies, a k mount and a m42), and I strongly suggest you find ways to stick around there. Purely my own opinion, based on shooting with the two lenses.
Oops! I was composing as you posted.!


Steve
06-28-2018, 01:50 PM   #13
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QuoteOriginally posted by stevebrot Quote
When adjusting infinity focus, the grub screws are backed out to release the ring, not removed
Actually, what I meant is that I have no screwdrivers to fit these screws ! screw me ! *cuff cuff* (sorry about the pun)

QuoteOriginally posted by stevebrot Quote
Do as you please with the rear filters. My experience was reduced sharpness away from center with no improvements in contrast or image quality.
Yeah I was expecting this...
QuoteOriginally posted by stevebrot Quote
BTW...Welcome to the Pentax Forums!
Thank you !

QuoteOriginally posted by stevebrot Quote
Almost forgot...X-mode is on the mode dial as a red "X" and is basically M mode with only one shutter speed, the X-sync speed for flash.
I don't have that on my K30, only P, Sv, Tv, Av, TAv, M, B, U2, U1, SCN, AUTO, *lil red camera*. But since my dial is screwed up (screw again) well I can only use TAv or P mode

Thanks everyone anyway ! You've helped me a lot, I hope to see you again right aroud there ! :P
06-28-2018, 01:58 PM   #14
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It's interesting to hear that Steve prefers his Zenitar with the rear filter while I prefer mine without it. I wonder if perhaps it's down to the notoriously wayward quality control with this lens, causing different copies to have different characteristics? Or perhaps we just have different preferences for the way we like a lens to render?
06-28-2018, 02:01 PM   #15
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QuoteOriginally posted by Dartmoor Dave Quote
It's interesting to hear that Steve prefers his Zenitar with the rear filter while I prefer mine without it. I wonder if perhaps it's down to the notoriously wayward quality control with this lens, causing different copies to have different characteristics? Or perhaps we just have different preferences for the way we like a lens to render?
Well I think no matter your tastes, something sharp is something sharp. It seems more logical to me that it is more sharp with the filter, but yeah, I'll do a benchmark some day

---------- Post added 06-28-18 at 02:06 PM ----------

QuoteOriginally posted by RedTurian Quote
It seems more logical to me that it is more sharp with the filter, but yeah, I'll do a benchmark some day
It seems LESS logical, sorry :P
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